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Title
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Bird Use of Epiphyte Resources in an Old-Growth Coniferous Forest of the Pacific Northwest
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Date
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2009
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Creator
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Wolf, Adrian Lance
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Subject
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Environmental Studies
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extracted text
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Bird use of epiphyte resources in an old-growth coniferous forest of the Pacific Northwest
by
Adrian Lance Wolf
A Thesis
Submitted in partial fulfillment
of the requirements for the degree
Master of Environmental Studies
The Evergreen State College
September 2009
This Thesis for the Master of Environmental Studies Degree
by
Adrian Lance Wolf
has been approved for
The Evergreen State College
by
________________________
Nalini Nadkarni, Ph.D.
Member of the Faculty
________________________
Dave Shaw, Ph.D.
Oregon State University
________________________
Steve Herman, Ph.D.
Member of the Faculty
________________________
Anne McIntosh, Ph.D Candidate.
University of Alberta
________________________
2 September 2009
ABSTRACT
Epiphytes play important ecological roles in the Pacific Northwest and elsewhere, but the
resources they provide for birds are poorly known. If epiphytes are an important foraging and
nesting resource for birds, current and future forest management activities may have negative
effects on bird community diversity and abundance. I used mountain-climbing techniques to
access the forest canopy to: 1) assess whether species and foraging guilds use host and epiphyte
resources in the same proportions relative to their availability; and 2) evaluate whether canopylevel and ground-level point count assessments are comparable methods for detecting forest birds.
I studied epiphyte use by birds in the T. T. Munger Research Natural Area, an old-growth
coniferous forest in the southern Washington Cascades. Approximately 30% of all foraging
records (N=735) occurred on epiphyte substrates. Chestnut-backed Chickadee, Red-breasted
Nuthatch, Brown Creeper, Hairy Woodpecker and Gray Jay used epiphytes disproportionately,
based on log-likelihood ratio tests. Bark insectivores and omnivore scavengers used cyanolichen
and other lichen and bryophytes disproportionately, relative to their availability. Use of lichen
substrates was more frequent than other epiphytes in the mid- and upper-crown, compared with
more frequent use of bryophytes than other epiphytes in the lower-crown. Alectorioid lichens
were used with hanging and probing behaviors, whereas foraging bouts on cyanolichen and other
lichen substrates involved a greater variety of foraging maneuvers and postures. Pseudotsuga
menziesii and Tsuga heterophylla were used disproportionately more frequently than any other
tree species, relative to their availability when epiphyte substrates were used. Although groundlevel foraging observations were important for determining which resources were used in the
mid- to lower-canopy and understory, ground-based observers could not reliably evaluate which
resources were used by small passerines in the upper canopy. Use of epiphyte substrates for
foraging appears to be a function of observer location, rather than actual resource selection.
Similarly, the location of the observer was an important determinant for recording the height of
bird foraging activity.
More species and individuals were recorded at the canopy-level than at the ground-level
and detection frequencies increased at the canopy level when sampling radii exceeded 30 m.
Although there were no differences in the rank order of species detections between canopy and
ground-level observers, the canopy-level observer detected a more species rich community,
relative to observer detections captured at the ground level.
Non-vascular epiphytes increased the inner canopy rugosity and provided important
ecological functions for higher trophic levels, including nesting and foraging habitat. In Oregon
and Washington, 100 bird species that breed in coniferous forests use bryophyte, lichen or
mistletoe in their nests. To provide prime foraging and nesting habitat for forest birds, land
managers should consider the epiphyte vegetative community structure within foraging and
nesting habitat. Forest managers should implement forest practices that maintain old-growth
structural characteristics to enhance epiphyte assemblages and associated bird species
communities.
TABLE OF CONTENTS
TABLE OF CONTENTS ........................................................................................................... iii
LIST OF FIGURES .................................................................................................................... v
LIST OF TABLES..................................................................................................................... vi
LIST OF APPENDICES .......................................................................................................... viii
ACKNOWLEDGMENTS........................................................................................................... x
INTRODUCTION ...................................................................................................................... 1
LITERATURE SUMMARY OF BIRD USE OF MOSSES AND LICHENS............................... 5
Introduction ............................................................................................................................ 5
Methods.................................................................................................................................. 6
Results of Literature Search .................................................................................................... 6
Discussion .............................................................................................................................. 9
STUDY SITE AND METHODS............................................................................................... 11
Study Area............................................................................................................................ 11
Foraging Observations .......................................................................................................... 14
Tree Plots ......................................................................................................................... 14
Walking Transects ............................................................................................................ 17
Foraging Data Collection ...................................................................................................... 17
Resource Availability ........................................................................................................... 19
Point Counts ......................................................................................................................... 21
Statistical Analysis ............................................................................................................... 22
RESULTS ................................................................................................................................ 26
Bird Use of Epiphytes........................................................................................................... 26
Epiphyte Specialization .................................................................................................... 31
Discussion ........................................................................................................................ 32
Spatial and Substrate Specialization ...................................................................................... 34
Discussion ........................................................................................................................ 40
Use of Resources and Availability ........................................................................................ 41
Epiphyte and Host Resource Use and Availability............................................................. 41
Tree Use and Availability ................................................................................................. 44
Discussion ........................................................................................................................ 47
Community Structure............................................................................................................ 49
iii
Results for Epiphyte Foraging Events ............................................................................... 49
Discussion ........................................................................................................................ 56
Comparison of Methods........................................................................................................ 59
Comparison between Tree Plot and Walking Transect Sampling Procedures ..................... 59
Comparison between Sampling Procedures for Epiphyte Use............................................ 64
Comparison between Sampling Procedures for Spatial and Substrate Specialization.......... 65
Comparison between Sampling Procedures for Resource Use and Availability.................. 69
Comparison between Sampling Procedures for Community Structure ............................... 71
Discussion ........................................................................................................................ 73
Comparison between Canopy- and Ground-Level Point Counts ........................................ 76
Core Species..................................................................................................................... 77
Discussion ........................................................................................................................ 82
DISCUSSION........................................................................................................................... 85
Ecological Roles of Epiphytes for the Bird Community .................................................... 85
Study Limitations ............................................................................................................. 93
CONCLUSION AND IMPLEMENTATIONS FOR FOREST MANAGEMENT ...................... 94
Epiphytes as Foraging Habitat............................................................................................... 94
Point Counts ......................................................................................................................... 95
Future Research.................................................................................................................... 96
Conclusions .......................................................................................................................... 96
LITERATURE CITED ............................................................................................................. 98
APPENDICES........................................................................................................................ 108
iv
LIST OF FIGURES
Figure 1: Location of Study Area ............................................................................................. 12
Figure 2: Location of Tree Plots and Walking Transect in the T. T. Munger Research Natural
Area ................................................................................................................................. 13
Figure 3: Conceptual rendering of the Tree Plot sampling area. ................................................ 16
Figure 4: Major resource allocation for seven avian foraging guilds.......................................... 30
Figure 5: Epiphytic group allocation for four avian foraging guilds .......................................... 30
Figure 6: Nonmetric multidimensional scaling ordination for 191 individuals with different
symbols for seven foraging guilds whose members foraged on epiphyte substrates............ 54
Figure 7: Nonmetric multidimensional scaling ordination for 191 individuals with different
symbols for fourteen species observed using epiphyte substrates in the Tree Plots............. 55
Figure 8: Venn diagram of species and foraging bouts captured by survey procedure................ 61
Figure 9: Histogram of canopy- and ground-level observer detection distances for nine core
species.............................................................................................................................. 81
Figure 10: Lobaria oregana at 30 m provide refugia for canopy arthropods.............................. 91
Figure 11: The broad thallus of Lobaria oregana, at 30 m capture seed rain and litterfall.......... 91
Figure 12: Platismatia glauca, a foliose lichen, provides habitat for a dipteran at 30 m............. 91
Figure 13: Alectorioid lichens on the bole of Pseudotsuga menziesii at 26 m. ........................... 91
Figure 14: At 30 m, Alectoria sarmentosa cloaks the foliage on Tsuga heterophylla................. 91
Figure 15: Appressed and pendant bryophytes cover the limbs of Taxus brevifolia. .................. 91
v
LIST OF TABLES
Table 1: Summary data for bird use of nesting material in North America, and for birds that
breed in coniferous forests of Washington and Oregon........................................................ 8
Table 2: North American birds that use Usnea lichen as nesting material.................................... 8
Table 3: Mean number of trees per Tree Plot by species and crown class. ................................. 15
Table 4: Estimated biomass, relative proportion and ratio of epiphyte groups ........................... 20
Table 5: Estimated stores of carbon from the Canopy Crane Plot .............................................. 20
Table 6: Relative availability of tree species ............................................................................. 21
Table 7: Total species observation time, number of foraging observations and sequences ......... 27
Table 8: Number of species, foraging guilds, and individuals that used epiphyte and other
substrates.......................................................................................................................... 29
Table 9: Percent total foraging, postures, maneuvers and foraging height of 12 bird species
searching epiphyte functional groups, relative to all foraging bouts ................................... 33
Table 10: Number of foraging bouts on lichen substrates by tree species/types ......................... 35
Table 11: Number of foraging bouts on bryophyte substrates by tree species/types. .................. 35
Table 12: Number of foraging bouts on epiphyte and phorophyte groups by tree class, tree status,
tree position, crown zone, posture and maneuver .............................................................. 37
Table 13: Percentage of foraging bouts by substrate among three height classes ....................... 38
Table 14: Mean foraging height and range of bird foraging guilds by substrate......................... 38
Table 15: Mean foraging height and range of all bird records by finer-scale substrates.............. 39
Table 16: Relative availability of host and epiphyte resources and their use by five species ...... 42
Table 17: Relative availability of epiphyte groups and their use by five species ........................ 43
Table 18: Relative availability of tree species and their use by all species during foraging bouts
on epiphyte and host substrates ......................................................................................... 45
Table 19: Relative availability of tree species and their use by seven foraging guilds during
foraging bouts on epiphyte and host substrates. ................................................................. 46
Table 20: Comparison of differences in epiphyte related foraging strategies with non-metric
Multi-Response Permutation Procedures........................................................................... 50
Table 21: Behavioral activity data summary by survey procedure............................................. 60
Table 22: Searching and foraging bout survey effort summary by survey procedure ................. 60
Table 23: Number of foraging species, individuals and foraging guilds detected per day and by
survey procedure. ............................................................................................................. 61
vi
Table 24: Total observation time, number of individuals and sequences for each species. ......... 62
Table 25: Number of foraging individuals detected per survey day and detection frequency ..... 63
Table 26: Mean foraging height of all bird records by substrate and survey procedure. ............. 66
Table 27: Mean bark insectivore foraging heights by substrate and survey procedure ............... 67
Table 28: Mean timber-foliage insectivore foraging heights by substrate and survey procedure 67
Table 29: Mean omnivore scavenger foraging heights by substrate and survey procedure ......... 68
Table 30: Relative availability of host and epiphyte resources and their use by five species by
survey procedure. ............................................................................................................. 70
Table 31: Relative availability of epiphyte groups and their use by five species by survey
procedure ......................................................................................................................... 70
Table 32: Comparison of differences in epiphyte-related foraging strategies with non-metric
Multi-Response Permutation Procedures........................................................................... 73
Table 33: Species diversity by point count observer location in unlimited-radius plots.............. 76
Table 34: Mean number of birds per plot for nine species by observer location......................... 78
Table 35: Frequency of occurrence of nine bird species by observer location............................ 79
Table 36: Comparison of detection distances for nine species by observer location................... 80
vii
LIST OF APPENDICES
Appendix A: North American and Oregon/Washington breeding birds that use non-vascular
plants, Spanish Moss, epiphytic rootlets, or mistletoe as nesting substrates...................... 108
Appendix B: Description of canopy observer height, climbing tree specifics and other associated
environmental variables within the Tree Plots ................................................................. 121
Appendix C: List of bird species detected in the T. T. Munger Research Natural Area............ 122
Appendix D: Comparative use of horizontal and vertical tree zones by four birds during foraging
bouts on host and epiphyte substrates, Tree Plots. ........................................................... 125
Appendix E: Comparative use of horizontal and vertical tree zones by four birds during foraging
bouts on host and epiphyte substrates, Walking Transects. .............................................. 126
Appendix F: Epiphyte and host use of tree classes by six foraging birds; Tree Plots and Walking
Transects. ....................................................................................................................... 128
Appendix G: Relative availability of host and epiphyte resources and their use by five species.129
Appendix H: Relative availability of epiphyte groups and their use by five species................. 130
Appendix I: Availability of tree species and their use by five species during foraging bouts on
epiphyte substrates.......................................................................................................... 131
Appendix J: Multi-Response Permutation Procedures pairwise comparisons by epiphyte foraging
activity ........................................................................................................................... 132
Appendix K: Multi-Response Permutation Procedures pairwise comparisons of foraging guilds
by epiphyte foraging activity........................................................................................... 135
Appendix L: Multi-Response Permutation Procedures pairwise comparisons of species by
epiphyte foraging activity. .............................................................................................. 136
Appendix M: Number of species, guilds, and individuals that used epiphyte, phorophyte and
other substrates by survey type. ...................................................................................... 138
Appendix N: Percent total foraging, postures, maneuvers, and mean foraging height of 6 bird
species searching epiphyte functional groups, relative to all substrates, Tree Plots only. .. 139
Appendix O: Percent total foraging, postures, maneuvers and foraging height of 12 bird species
using epiphytes, relative to all foraging substrates, Walking Transects only..................... 140
Appendix P: Multi-Response Permutation Procedures pairwise comparisons of finer scale
epiphyte substrates used by all birds observed, Tree Plots and Walking Transects. .......... 141
Appendix Q: Multi-Response Permutation Procedures pairwise comparisons of foraging guilds
by finer-scale epiphyte substrate foraging activity, Tree Plots and Walking Transects. .... 142
viii
Appendix R: Mean number of birds detected in 30 m- and unlimited-radius plots................... 143
Appendix S: Frequency of occurrence of all bird species by observer location........................ 144
Appendix T: Histogram of canopy- and ground-level observer detection distances for nine
species............................................................................................................................ 145
ix
ACKNOWLEDGMENTS
Thanks to my thesis committee members, Drs. Nalini Nadkarni, Dave Shaw, Steve
Herman, and Anne McIntosh, for their support and encouragement. My earnest gratitude goes to
The International Canopy Lab and Canopy Database Project, namely Anne McIntosh, Juli Perry
and Judy Cushing – the Access Database made data transcription somewhat enjoyable. Thanks to
The International Canopy Network, Olympia WA, for access to equipment and scientific
literature. Other valued assistance with methodology and data analysis was provided by Carri Le
Roy, Alison Styring, Dave Watson, Nathaniel Seavy and Jennifer Weikel. Anne McIntosh, Carri
Le Roy, and Dr. Bruce McCune provided valuable guidance with PC Ord and interpreting NMS
and MRPP. Ken Bible and Annette Hamilton at the Wind River Canopy Crane Research Facility
(WRCCRF) were most helpful; and WRCCRF provided housing and loaned field equipment.
Martin Hutten confirmed identifications of bryophytes and lichens. Dr. Howard Bruner, Oregon
State University, provided T. T. Munger plot data from the Permanent Study Plot program, a
partnership between the H. J. Andrews Long-Term Ecological Research program and the U.S.
Forest Service Pacific Northwest Research Station, Corvallis, Oregon. Thanks to Drs. Tom Spies
and David Manuwal for providing information on the RNA. Much appreciation to Sarah Greene,
at the Forest Science Lab, for the RNA permit. Sincere thanks to Ingrid Gordon, of Gear for
Good, Inc., who donated climbing equipment; and to Deane Rimerman who spent many hours in
the RNA maneuvering through the tangled understory and over coarse woody debris to assist with
tree rigging. Last, I thank Stuart Johnston, field ornithologist extraordinaire, for his persistence,
stamina, and early morning commutes from White Salmon. Without his expertise and patience,
this study would not have been possible. Funding assistance was provided by E. Alexander
Bergstrom Memorial Research Reward, the Northwest Scientific Association Student Research
Grant Award, MES Studebaker Fellowship, and NSF Canopy dB grant (DBI-0417311).
x
These arboricolous plants turn tree limbs into Babylonian hanging gardens.
Edward O. Wilson, The Diversity of Life
xi
CHAPTER 1
INTRODUCTION
Epiphytes fulfill important ecological functions in forest ecosystems (Coxson and
Nadkarni 1995, Rhoades 1995). Epiphytic cryptogams intercept precipitation, fog and mist, and
retain aerosol-delivered nutrients, fix nitrogen (Pike 1978, Nadkarni 1986, Nash 1996); and
supply forests with a nutrient subsidy via litterfall and throughfall (Reynolds and Hunter 2004).
These arboreal communities also provide critical microhabitats for invertebrates, and vertebrate
resources for insectivorous and non-insectivorous bird species (Pettersson et al. 1995, Muir et al.
2002). Coniferous forests in the Pacific Northwest (PNW) harbor a tremendous diversity of
epiphytes, which reach their greatest diversity in old-growth stands (McCune 1993). Canopy
epiphyte biomass in the PNW is as high as 2.6 tons ha -1 (McCune 1993) and lichens alone may
contribute up to 7.5 kg ha-1 yr-1 of nitrogen to nutrient poor forests (Pike 1978).
Considerable ornithological research has been conducted in the PNW, most studies have
primarily focused on patterns of avian abundance and distribution between different aged stands
and forest types (e.g., Manuwal 1991, Manuwal and Carey 1991, Ruggiero et al. 1991, Sharpe
1996). These studies have positively correlated bird species richness and species abundance with
old-growth forest, with the relationship attributed to complex structural features of the forest.
The crowns of old-growth conifers offer tremendous structural diversity in foliage, branch forms,
snags, cavities and epiphytic communities (Shaw et al. 2002). However, no studies in the PNW
have considered the ecological relationship of epiphytic resources and birds, due to the difficulty
of accessing the canopy for direct observations (Munn and Loiselle 1995), the apparent lack of
epiphyte specialists (Sillett 1994), and the focus of research on the two federally threatened
species (the Northern Spotted Owl (Strix occidentalis caurina) and Marbled Murrelet
(Brachyramphus marmoratus)). Thus, the ecological roles of and resources that PNW epiphytes
provide for vertebrates are poorly known, particularly for birds.
My primary objective was to assess bird use of epiphytes. Research in tropical forests
has demonstrated that birds use canopy epiphytes extensively, and their presence in forests may
contribute to bird community diversity (Terbough 1980, Nadkarni and Matelson 1989, Nadkarni
1994, Sillett 1994). Tropical birds are rewarded with nectar, resins, or pollen, rewards that do not
exist in temperate coniferous forest canopies because the temperate arboreal epiphyte community
is almost entirely composed of non-vascular plants (McCune et al. 2000). Epiphytes may add to
the available pool of ecological niches, or auxiliary resources by increasing the surface area of the
1
forest canopy. This hypothesis has been proposed (Nadkarni and Matelson 1988) and tested
(Cruz-Angon et al. 2008) in tropical forest ecosystems but has not been tested in temperate
forests.
Mosses and lichens are used by temperate coniferous forest birds as nesting substrate
(Sharnoff and Rosentreter 1998), but do these birds also use these substrates for foraging? A
diverse range of biotic and abiotic variables affect bird foraging patterns and substrate selection,
but optimal foraging theory suggests that birds will optimize and maximize their successes in
procuring food by spending most of their foraging efforts searching substrates most likely to
harbor rewards (Pyke 1984, Morse 1990). Differential foraging strategies by foraging guilds and
their representative species contribute to increased niche partitioning and increased forest
diversity. I collected foraging observations from the canopy and ground level to determine the
relative frequency of specific substrates use by foraging birds. This revealed the relative
importance of each substrate for each species and respective foraging guild, and allowed a
comparison between species and foraging guilds. My alternate hypothesis is that there are
difference among species and foraging guilds: species and foraging guilds will use epiphytes
disproportionately using dissimilar foraging strategies and behaviors.
The importance of canopy epiphytic resources has been documented for certain temperate
bird species. The federally threatened Marbled Murrelet uses an epiphytic moss (Isothecium
spp.) extensively as a nesting substrate (Hamer and Nelson 1995). Sillett (1994) reported that
some birds use epiphyte resources in parts of their range during certain times of the year,
although he also noted that there were no epiphyte specialists in temperate and arctic North
America and Greenland. Birds avoided fruticose lichen and foliose species presumably because
the lichens contained anti-herbivory compounds (Sillett 1994). However, PNW canopy foliose
lichen and bryophyte mats provide suitable microhabitat for, and harbor a unique assemblage of
arthropods (Winchester and Ring 1994, Schowalter and Ganio 1998, Behan-Pelletier and Eamer
2001). Thus, temperate forest epiphytes provide foraging birds rewards, albeit indirectly. I
suggest that all epiphyte functional groups provide additional vertical and horizontal strata that
increase the structural and functional diversity of canopy resources, thus increasing foraging and
nesting opportunities for insectivorous birds.
Birds may contribute to epiphyte reproduction by acting as agents of dispersal for
vascular and non-vascular plant species (Rhoades 1995, Benzing 2004). This could account for
higher epiphyte species richness (McCune et al. 2000) and an increase in bird abundance reported
in the upper canopy, relative to the ground level and lower canopy (Shaw et al. 2002). Therefore,
not only may epiphytes provide “new” resources for birds otherwise limited to resources of the
2
host tree, but also the birds could be facilitating dispersal of propagules and spores among
epiphyte populations.
Branch forms and branch distribution influence the composition of epiphytic
communities in old-growth forests, and epiphytes within old-growth forest canopies are not
randomly or evenly distributed: the foliage supports the bulk of epiphytic lichen biomass,
followed by branches, and finally trunks (Clement and Shaw 1999). Vertical stratification of
epiphytic functional groups occurs (McCune 1993, Clement and Shaw 1999, McCune et al. 2000)
and vertical stratification also occurs in some songbird assemblages (Shaw et al. 2002). Thus, I
postulate that the gradient in epiphyte groups might influence vertical stratification observed in
birds if certain epiphytes groups are more important foraging resources than other epiphyte
groups.
The response of epiphytes to forestry practices has received considerable attention in the
past three decades (McCune 1993). Experimental studies have documented that certain epiphytes
are dispersal limited while others may be limited by substrate or micrometeorological conditions
(Pike 1978, McCune 1993, Peck and McCune 1997, Sillett and Goslin 1999). Although we can
generally predict how certain epiphyte species respond to changes in age class and canopy
structural modifications, we cannot predict how these changes alter epiphyte communities and
associated fauna, including bird communities. The effects of forest management on lichen and
invertebrate communities and passerine birds have been investigated in other countries
(Pettersson et al. 1995, Uliczka 1999). For example, Uliczka (1999) correlated the absence of
certain lichen and bird species in heavily managed boreal forests in southern Sweden. This hole
in our knowledge limits our ability to manage lands to promote biodiversity.
In the PNW, forest management goals for state and federal forests (the “matrix”) entail
harvest rotations of 40 to 80 years, stands that have poorly developed epiphyte communities
(McCune 1993). Thus, if epiphytes are an important foraging and nesting resource for birds,
current and future management activities may have negative effects on bird community diversity
and abundance. Spickler et al. (2006) suggested that epiphyte productivity and the associated
humus mats that develop in old-growth conifer crowns may maintain a diverse community of
nutrient dependant organisms. These structurally complex crowns of old-growth forest stands
may contribute to increased foraging opportunities for birds, which might account for higher bird
species richness and abundances reported for old-growth stands, relative to young stands
(Manuwal 1991, Huff and Raley 1991, Huff et al. 1991).
A secondary objective was to assess whether point counts conducted at the ground level
are a reliable census technique for forest birds. Point counts are a common census technique used
3
to estimate species richness, densities and abundances of bird populations. The accuracy and
precision of these estimates relies on them meeting certain assumptions (Bibby et al. 1992,
Buckland et al. 1993). Among-observer sources of bias and error associated with these estimates
vary according to environmental factors including vegetation and background noise (e.g., Waide
and Narins 1988, Kissling and Garton 2006, Simons et al. 2007, Pacifici et al. 2008). Groundbased techniques, such as double-observer sampling, have been developed to assess the amount
of error and bias in these distance sampling estimates (e.g., Kissling and Garton 2006). However,
few studies have evaluated among-observer variability, particularly when double-observer
sampling is conducted simultaneously and vertically in dense forests with high canopies (Waide
and Narins 1988, Anderson 2009). This evaluation is important because one of the key
assumptions of distance sampling theory is that the probability of detecting all birds at the plot
center is 1, which is unlikely in forests with high canopies (DeSante 1981). For example, groundlevel observers in a tropical forest underestimated the population of singing canopy birds by as
much as 50% (Waide and Narins 1988, Anderson 2009). Thus, if more species and individuals
could be recorded by a canopy observer, relative to a ground-level observer, then species richness
and abundances that characterize a temperate forest stand may historically have been
underestimated, since most forest bird assessments are conducted at ground level. Amongobserver variability of canopy- and ground-level point counts were compared to assess whether
ground-level point count assessments are a reliable method for detecting forest birds. I postulate
that point counts conducted at the canopy level facilitate a more comprehensive assessment of
species richness, abundance and detection frequencies in both fixed and unlimited radii plots.
The study was comprised of two parts: 1) a literature review of North American species
accounts of bird use of epiphytes and 2) field surveys. I provide information on the roles that
epiphytes provide for PNW forest birds, and compare differences between canopy- and groundlevel observers. My goals are to:
1. Quantify the frequency of bird use of epiphyte resources, and whether birds use epiphyte
resources in proportion to their availability, relative to other forest resources;
2. Identify foraging guild or species epiphyte specialists;
3. Identify the epiphyte foraging strategies used by foraging guilds and species;
4. Compare species richness and relative abundances between canopy- and ground-level
observers in variable circular plot point counts;
5. Suggest epiphyte/bird roles in forest ecology; and
6. Outline management implications of these findings.
4
CHAPTER 2
LITERATURE SUMMARY OF BIRD USE OF MOSSES AND LICHENS
Introduction
Although lichens and mosses are considered critical components of many food chains,
there is a paucity of published information on the ecological roles that these non-vascular plants
provide for wildlife, especially birds (Sharnoff and Rosentreter 1998). Most literature on the
matter has focused on lichens as an important forage base for caribou and other ungulates. For
instance, the North American Caribou (Rangifer tarandus) is known to eat pendant epiphytic
forage lichens that cloak old-growth forest canopies, including species of Alectoria, Bryoria, and
Usnea (Richardson and Young 1977).
Although it was generally accepted that birds use lichens and bryophytes for nest
structure, function and ornamentation, the listing of the Northern Spotted Owl and Marbled
Murrelet as federally-threatened species validated the importance of bryophytes and lichens as
nesting material as well as food for a variety of birds, bats, and rodents dependant on old-growth
forests (FEMAT 1993). The Northern Spotted Owl and Marbled Murrelet rely either directly or
indirectly on the presence of these cryptogams. For instance, the Marbled Murrelet uses moss
mats as a nesting platform, and the Northern Spotted Owl eats Northern Flying Squirrel
(Glaucomys sabrinus), which uses lichens and moss extensively for food and in its nests
(FEMAT 1993).
Birds use bryophytes and lichens as inner or outer nest lining, or for ornamentation of the
outside, and the nest functions provided by bryophytes and lichens include insulation,
camouflage, and possibly predator avoidance mechanisms. Lichens and bryophytes also provide
North American passerines with a forage base by affording invertebrates both food and protective
environments for shelter, oviposition and pupation sites (Seaward 1977, Smith 1982). Lichenand bryophyte-associated invertebrates include terrestrial fauna such as mites, annelids, mollusks
and other arthropods (Gerson and Seaward 1977, Gerson 1982). These invertebrates provide a
foraging base for vertebrates including insectivorous birds.
If birds use mosses and lichens extensively for nesting substrate and forage, then the
presence of these non-vascular plants may contribute to bird community diversity in these
temperate forests. A review of the literature was warranted to identify the bird species that use
cryptogams in nest construction and use lichens or mosses directly as a food source.
5
Methods
I reviewed the literature on bird use of epiphytic resources (primarily bryophytes and
lichens) as nesting substrates in North America (Gabrielson and Jewett 1970; Seward 1977,
Ehrlich et al. 1988; Marshall et al. 2003, Baicich and Harrison 2005, Wahl et al. 2005; and two
surveys of lichens and their use by North American wildlife and invertebrates [Sharnoff and
Rosentreter 1998, Sharnoff 1998]). In addition; I reviewed a subset of entries (239 species) from
the Birds of North America online electronic resource (Cornell Lab of Ornithology 2009), which
included 151 bird species known to breed in forested habitats in Oregon (Oregon Bird Records
Committee 2008, Marshall et al. 2003) and Washington (Washington Ornithological Society
2008, Wahl et al. 2005). The species reviewed included all members of the Orders
Falconiformes, Strigiformes, Apodiformes, Piciformes, and Passeriformes, and species that breed
in coniferous forests (e.g., Ruffed Grouse, Band-tailed Pigeon). The species accounts in the
citations were reviewed to determine the number of bird species that use epiphytic resources for
nesting in a) North America, and b) and Oregon (OR) and Washington (WA).
Results
Of a total of 670 bird species that nest in North America (Baicich and Harrison 2005), at
least 279 species (42%) use one or more of the five common epiphyte substrates: 1) bryophyte, 2)
lichen, 3) Spanish Moss, 4) epiphytic rootlets, and 5) mistletoe, for nesting, including structural,
nest ornamentation or lining purposes (Table 1; see Appendix A for a complete list of species and
substrate use). Nearly 40% (262 species) of North American birds use either lichens or
bryophytes as a nesting substrate or as nesting material. At least 21 North American birds use the
epiphytic vascular plant, Spanish moss (Tillandsia usneoides) as nest material (Appendix A).
Of the 151 bird species that breed in coniferous forests of OR and WA, 98 species (65%)
use either lichen or moss; and 45 species (30%) use both lichen and moss as nesting material
(Table 1). Thus, the proportion of birds that use bryophytes and breed in OR and WA coniferous
forests is almost double the proportion of North American birds that use bryophytes. Similarly,
although not quite as extreme, a greater proportion of WA and OR forest breeding birds use
lichens (35%), relative to the proportion of North American birds that use lichen (19%). In OR
and WA coniferous forests, all seven thrush (Turdidae) and six hummingbird species
(Trocholidae) use either bryophyte or lichen as nesting material (Appendix A). All nine crows
and jays (Corvidae), except one (Black-billed Magpie), use bryophytes in their nests. Similarly,
6
10 of 11 OR and WA breeding fringilline finches (Fringillidae) use either moss or lichen.
Bryophytes and lichens are frequently used as nesting material by 8 of 12 (67%) tyrant
flycatchers (Tyrannidae), and by 8 of 11 wood warblers (Parulidae).
At least 14 bryophyte and ten lichen genera are used by breeding birds in coniferous
forests: The bryophyte genera used included Alsia, Brachythecium, Calliergon, Dendroalsia,
Dicranum, Eurhynchium, Homalothecium, Hypnum, Isothecium, Pogonatum, Pohlia,
Polytrichum, Porella, and Sphagnum. The bryophyte genera Alsia, Dicranum, Hypnum,
Isothecium, and Porella generally have epiphytic forms, whereas Eurynchium is primarily
terrestrial although Eurynchium often grows on the bases of tree boles and on fallen logs. The
lichen genera included Alectoria, Bryoria, Cladonia, Evernia, Hypogymnia, Parmelia, Physcia,
Ramalina, Sphaerophorus, and Usnea. With the exception of Cladonia, all lichen genera are
generally epiphytic, growing on bark and wood of coniferous and deciduous trees (McCune and
Geiser 1997). Twenty North American bird species use Usnea lichen as either the primary
structure or lining for their nest substrates (Table 2). Eleven of the 20 species that use Usnea
lichen breed in OR and WA and locate their nests in coniferous trees; seven species, Fox
Sparrow, Golden-crowned Kinglet, Gray Jay, Hutton’s Vireo, Marbled Murrelet, Red Crossbill
and Ruby-crowned Kinglet are year-round residents, and all four tyrant flycatchers are
neotropical migrants.
Several bird species that breed in coniferous forests use nests made almost entirely of
mosses. Examples include the Winter Wren (Hejl et al. 2002), Marbled Murrelet (Nelson 1997)
and Golden-crowned Kinglet (Ingold and Galati 1997). A Hammond Flycatcher nest described
by Sakai (1988) was comprised of two epiphytic lichens (Hypogymnia inactiva and Ramalina
menziesii), and five bryophytes (including the epiphytic moss Isothecium sp., and liverwort,
Porella navicularis). Two other Neotropic migrants (Pacific-slope Flycatcher and Hutton’s
Vireo) use the epiphytic lichen R. menziesii.
7
Table 1: Summary data for bird use of nesting material in North America, and for birds that
breed in coniferous forests of Washington and Oregon.
NORTH AMERICA
No. of Species
Percent*,**
223
127
10
262
88
21
279
33
19
1
39
13
3
42
151
90
53
98
45
100
23
60
35
65
30
66
bryophyte
lichen
mistletoe
lichen or bryophyte
lichen and bryophyte
Spanish moss
either bryophyte, lichen, Spanish Moss, epiphytic rootlets or mistletoe
WASHINGTON AND OREGON
Coniferous forest breeding birds**
bryophyte
lichen
lichen or bryophyte
lichen and bryophyte
either bryophyte, lichen, or mistletoe
* percentages are based on a total of 670 species occurring in North America (Baicich and
Harrison 2005); and ** 151 breeding birds in Washington and Oregon (Marshall et al. 2003,
Wahl et al. 2005)
Table 2: North American birds that use Usnea lichen as nesting material.
English Name
Red-shouldered Hawk
Marbled Murrelet
Olive-sided Flycatcher
Dusky Flycatcher
Pacific Flycatcher
Hammond's Flycatcher
Gray Jay
Golden-crowned Kinglet
Ruby-crowned Kinglet
Bohemian Waxwing
Philadelphia Vireo
Hutton's Vireo
Northern Parula
Blackburnian Warbler
Blackpoll Warbler
Fox Sparrow
Rusty Blackbird
Common Grackle
Red Crossbill
Common Redpoll
OR/WA
breeder?
yes
yes
yes
yes
yes
yes
yes
yes
yes
no
no
yes
no
no
no
yes
no
no
yes
no
Nest host/location
Deciduous tree
Conifer
Conifer
Deciduous tree, Conifer, Shrub
Deciduous tree, Conifer
Deciduous tree, Conifer
Conifer
Conifer
Conifer
Conifer
Deciduous tree
Deciduous tree, Conifer
Deciduous tree
Conifer
Conifer
Conifer
Conifer, Shrub
Deciduous tree, Conifer
Conifer
Shrub
Winters in
OR/WA
yes
yes
no
no
no
no
yes
yes
yes
yes
no
yes
no
no
no
yes
yes
no
yes
yes
8
Discussion
Thus, many bird species use cryptogams in nest construction. This literature review was
not exhaustive since many nest details were defined in broad categories. For some species, the
nest descriptions provided were coarse categories, such as “plant debris” or “plant fibers”,
whereas for others, the nest details were meticulous. For instance, the nest of the Townsend’s
Warbler was described as being “lined with moss fruiting stems and hair”, and the Worm-eating
Warbler uses hair moss stems in the genus Polytrichum (Baicich and Harrison 2005). For some
species, the breeding ecology and nest details are poorly understood (e.g., Hermit Warbler
[Pearson 1997]). These data should also be considered an underestimate because several North
American species use abandoned nest sites or are brood parasites of species known to use
epiphytes for nest substrates (e.g., genera Molothrus). Furthermore, the nest substrate data in the
literature reviewed did not specify whether the bryophytes and/or lichen used were epiphytic
forms. Bryophyte and lichen forms may be terrestrial, epilithic (dwelling on rocks) or epiphytic.
This literature search more than doubled the number of North American birds that use
lichens in their nests to 127 species, from 45 (Richardson and Young 1977). The common use of
lichens by birds for nesting is believed to be an evolutionary adaptation that aids in nest
concealment (Richardson and Young 1977). That the terms decoration and ornamentation are
often used to describe lichen use diminishes the functional ecological role of lichens. Not only do
lichens provide aesthetic and camouflage, lichens likely play a significant role in maintaining nest
health, since several lichen species (e.g., Lobaria pulmonaria) have antimycobacterial properties
(Boustie and Grube 2005). Lichens waterproof nests by shedding water (Ehrlich et al. 1988), and
darker-colored lichens used often as nest material in colder climates (e.g., Bryoria spp.) have
insulating properties, because they more readily absorb solar radiation than lighter-colored
materials. Because 19% of North American birds (and 35% of birds that breed in coniferous
forests in OR and WA) use lichens for nesting substrates, birds may function as a dispersal agent.
This has important implications for lichen conservation and management objectives of many
dispersal-limited epiphyte species. However, birds may or may not represent a significant
pathway of dispersal.
Birds rarely use lichens or bryophytes as food, except in times of food shortages (Sillett
1994, Rhoades 1995). Possible explanations for the limited use of these cryptogams are the low
caloric value and presence of toxic compounds (Rhoades 1995). However, there were several
accounts of species eating bryophytes, but fewer accounts for lichen. Most accounts were for
species that breed in the colder climates of North America (e.g., the Red-throated Loon, Brant,
9
and three cogenerics of Ptarmigan, White-tailed, Willow, and Rock Ptarmigan) (Palmer 1962,
Martin and Hik 1992, Braun et al. 1993, Hannon et al. 1998). Sporophyte capsules of Distichum
incinatum comprised a substantial proportion of the crop contents of some Willow Ptarmigan
chicks (Martin and Hik 1992). Possible explanations for these Canadian Arctic breeders eating
mosses might be because several arctic bryophytes contain higher percentages of lipids, relative
to their vascular plant counterparts (Pakarinen and Vitt 1982), providing high quality food.
Canopy epiphytic mosses and lichens indirectly provide important food sources for
invertebrates, and egg laying sites, on which birds depend (Gerson and Seaward 1977). Any
modification or disruption of these epiphyte communities may have a deleterious effect for higher
trophic levels.
10
CHAPTER 3
STUDY SITE AND METHODS
The field survey component included 1) foraging data collected from fixed-area plots and
walking transects, and 2) simultaneous canopy- and ground-level variable circular plot point
counts.
Study Area
The field study site was the 478 ha Thornton T. Munger Research Natural Area (RNA)
located in the 4208-ha Wind River Experimental Forest located in the southern Cascade Range of
Washington State (latitude N 45o49’13.76”, longitude W 121o57’06.88”; Fig. 1). Sampling was
conducted in an approximately 500-year-old Douglas-fir (Pseudotsuga menziesii (Mirbel)
Franco) – western hemlock (Tsuga heterophylla (Raf.) Sarg.) coniferous forest (Shaw et al.
2004). The RNA supports a transitional vegetation zone between the Western Hemlock Zone and
the Pacific Silver Fir Zone (Franklin and Dyrness 1973). The RNA occurs on an extinct shield
volcano, topography is gentle, and elevation ranges from 335 m to 610 m (Meyers and Fredricks
1993). The climate is characterized by summer droughts, winter snow events, with mean annual
precipitation of approximately 2.2 m per year (Shaw et al. 2004). The Wind River Canopy Crane
Research Facility located in the southeastern portion of the RNA, has facilitated extensive forest
canopy research in this old-growth forest ecosystem. Previous work on epiphytic abundance and
distribution (McCune 1993, Clement and Shaw 1999, McCune et al. 2000, Shaw et al. 2002,
Nadkarni and Sumera 2004) has been conducted in the vicinity.
11
Figure 1: Location of Study Area.
12
Figure 2: Location of Tree Plots and Walking Transect in the T. T. Munger Research Natural
Area.
13
Foraging Observations
I followed the field research protocol of Nadkarni and Matelson (1989) and Sillett (1994),
and used two sampling procedures to collect data on bird foraging behavior and substrate use: 1)
fixed-area plots (hereafter referred to as Tree Plots), and 2) Walking Transects. Surveys were
conducted between 25 April and 7 July 2005 for a total of 40 survey days totaling 337.6 survey
hours: 122.7 Tree Plot hours (mean survey length = 3.07 hrs, SE = 0.02); and 214.9 Walking
Transect hours (mean survey length = 5.4 hrs, SE = 0.03). Total distance traversed during the
Walking Transects was 96 km, which captured approximately 288 km2 of the RNA. The 20 Tree
Plots captured approximately 1.4 km2 of the RNA.
Tree Plots
Twenty Tree Plots were selectively located in existing permanent growth and mortality
study plots located within the RNA (Meyers and Fredricks 1993, Fig. 2). Tree Plots were 30 m
radius semi-circular viewing arenas at two levels in the forest: i) lower zone: 0 – 30 m; and ii)
upper canopy-level zone: 30 m – 60 m (Fig. 3). In general, Tree Plots were located a minimum
distance of 400 m from another. In each Tree Plot, a dominant or codominant tree was selected
as the climbing tree with the following criteria: 1) safety, 2) a suitable viewing arena around
which the observations could be conducted, and 3) within the long term monitoring plots in the
RNA.
The cumulative mean number of dominant, codominant and intermediate trees per Tree
Plot was 21.2 ( 1.2 SE), with the majority of these tree classes represented by T. heterophylla
(11.7 1.1 SE) and P. menziesii (6.1 1.1 SE) (Table 3). The maximum number of dominant
and codominant P. menziesii and T. heterophylla within any given plot was 17 (120 ha-1) and 15
(106 ha-1), respectively. The total number of trees per plot (excluding suppressed trees) ranged
from 12 to 31 (85 to 219 trees ha-1). Including all tree classes, the mean number of trees per plot
was 42.6 ( 4.0 SE), with 17 to 89 trees per plot (approximately 120 to 630 trees ha-1). Thuja
plicata is generally rare across the plots with the exception of the southeastern portion of the
RNA. Cover, based on Lemmon (1956), of the overstory canopy vegetation within the 30 mradius plot ranged from 75% to 95%. For additional information on RNA vegetation
composition, see Meyers and Fredericks (1993) and Shaw et al. (2004).
14
Table 3: Mean number of trees ( SE) per Tree Plot by species and crown class1.
Tree Species
Pseudotsuga menziesii
Tsuga heterophylla
Abies spp.
Thuja plicata
Taxus brevifolia
Cornus nuttallii
Snags
Total
1
Dominant
Codominant
Intermediate
Suppressed
Total
4.44 (0.76)
4.56 (0.85)
0.19 (0.10)
0.94 (0.94)
------10.69 (0.80)
1.50 (0.52)
3.06 (0.58)
050 (0.20)
0.13 (0.13)
------5.63 (0.77)
0.19 (0.10)
4.06 (0.51)
1.50 (0.44)
0.13 (0.09)
------5.94 (0.80)
0.00
8.88 (1.43)
6.19 (2.75)
0.00 (0.00)
4.81 (1.30)
0.44 (0.27)
--20.38 (4.02)
6.13 (1.14)
20.56 (1.74)
8.5 (2.76)
1.19 (1.12)
4.81 (1.30)
0.44 (0.27)
4.69 (1.12)
42.63 (4.03)
Smith et al. 1997
In each Tree Plot, a climbing rope was placed in the target tree to allow the canopy
observer to gain access to the upper canopy approximately 30 m above the forest floor (Fig. 3).
At least one day prior to data collection, trees were rigged and the perimeter of the 30-m
semicircular viewing arena (ground level) was marked with flagging tape. The climbing rope
was set the day before to minimize disturbing birds. On the morning of the observations, one
observer (“the upper zone observer”) gained access to the upper zone using single rope climbing
methods (Perry 1978). The upper zone observer was located in a fixed position, perched on a
“tree seat” attached to the bole of the tree, enabling the observer to conduct observations in a 180o
viewing arena while seated or standing and minimizing damage to sensitive canopy resources.
The upper zone observer was not expected to affect bird behavior (Nadkarni and Matelson 1989).
A second observer on the forest floor (“the lower-zone observer”) documented observations in
the lower zone. The lower-zone observer walked around the periphery of the 30 m semicircular
viewing arena to maximize detections, and the observers surveyed the zones simultaneously.
Only one Tree Plot was surveyed on any given day so that observations could be conducted
during the mornings when bird activity was greatest. The foraging observation sessions were
typically initiated within 1 hour after dawn, and lasted three hours.
The mean height of the tree seat from where the canopy observer conducted the foraging
observations and canopy-level point counts was 31.4 m ( 0.2 SE). The maximum tree seat
height was 43 m, in a P. menziesii, and the lowest canopy observation location was 25 m, in a T.
heterophylla (Appendix B). The overall height of the forest canopy was between 40 and 70 m.
Seventy percent of the dominant and codominant trees climbed were T. heterophylla, the
remaining trees were P. menziesii (25%) and one Abies grandis (5%).
15
Figure 3: Conceptual Rendering of the Tree Plot Sampling Area.
16
Walking Transects
The Walking Transects followed an existing 4.8 km trail through the RNA (Fig. 2). Two
observers conducted the Walking Transect surveys at ground level, with observers beginning
foraging observations at opposite ends of the Walking Transect. Flagging tape denoted each 0.1
km interval, allowing observers to calculate distances along the transect. They recorded foraging
birds opportunistically while walking along the survey route, and also paused at each 0.1 km
marker for 3 min (Weikel and Hayes 1999). Individual bird activities were recorded if they
occurred within 30 m of either side of the trail. To avoid collecting sequential conspecific
observations in the Walking Transects, sequential records for most small passerines (e.g.,
Chestnut-backed Chickadee and Golden-crowned Kinglet) were only collected after moving >80
m from the prior observation; sequential foraging data for larger passerines (e.g., Hairy
Woodpecker, Red Crossbill and Gray Jay) were only considered when distances between
observations exceeded 200 m. The Walking Transect survey concluded when the observers met.
The Walking Transects did not overlap or interfere with any of the Tree Plots (Fig. 2).
Foraging Data Collection
Individual birds were observed for the entire period they were visible within the Tree Plot
viewing arena or within 30 m of either side of the Walking Transect trail. Each foraging
sequence was timed and the following data were recorded: 1) foraging substrate (e.g., epiphyte
versus host, see below), 2) tree species, 3) estimated bird height in the tree, 4) crown class
(dominant, codominant, intermediate and suppressed, Smith et al. 1997), 5) horizontal crown
zone (inner, mid and outer) and vertical crown zone (above, upper, mid, lower and below live
crown, Lyons et al. 2000), 6) tree position (on what structure in the tree was the bird, e.g., bole,
foliage, branch), 7) tree condition (live or dead), 8) type of foraging maneuver, 9) foraging
posture, and 10) location along the transect (Walking Transect only). As a bird foraged, we noted
when a bird changed substrates, tree species, foraging behaviors, or foraging height. Therefore,
any change was considered a sequential foraging sequence, and multiple foraging sequences were
recorded for the same individual. Foraging behaviors (postures and maneuvers) followed
Remsen and Robinson (1990). Foraging postures included hang, hang upside-down, hop, lean
17
into, perch, reach under, reach up, sally, and short flights. Foraging maneuvers included glean,
hammer, peck, pluck, probe, and search.
Epiphytes were defined as bryophytes and lichens growing directly on the surface of
living trees and shrubs or dead stumps or logs. Epiphyte categories (following McCune 1993) to
classify epiphyte foraging substrate included: 1) alectorioid lichen (e.g., Alectoria spp., Bryoria
spp. Usnea spp.), 2) fruticose lichen (other than alectorioid lichen, e.g., Ramalina spp.), 3) foliose
lichen (other than Lobaria spp., e.g., Platismatia spp.), 4) other lichen (e.g., Cladonia spp.), 5)
bark lichen (i.e. crustose lichens, e.g., Physcia spp.) , 6) cyanolichen (e.g., Lobaria spp.), 7)
pendant bryophytes (e.g., Isothecium myosuroides Brid. and Antitrichia curtipendula (Hedw.)
Brid.), 8) cushion mosses (e.g., Dicranum fuscescens Turn.), and 9) prostrate mosses (e.g.,
Rhytidiadelphus loreus (Hedw.) Warnst.)). The categorical variable “bark lichen” included:
finely appressed crustose lichens; Sphaerophorus globosus (Huds.) Vain.; thin, strongly
appressed strands of corticolous bryophytes, (e.g., Hypnum circinale Hook); and other associated
corticolous lichen forms (e.g., Cladonia spp.). Closely appressed, corticolous, alectorioid lichens
were considered unique features of the bole, and dissimilar from the pendant forms common in
the outer canopy. Saxicolous species growing on logs and dead wood were considered epiphytic.
Epiphytic categories were pooled into groups (McCune 1997) for data analysis: 1) alectorioid
lichens, 2) cyanolichens and other lichens, 3) bryophytes, and 4) lichen/bryophyte admixture.
Non-epiphytic substrates included biotic substrates provided by the host (phorophyte)
including bark, branchlets, wood, live foliage, flower, and cone. Phorophyte resources also
included woody debris (large horizontal boles and associated limbs), components on the forest
floor that characterize old-growth stands. The dead woody debris supports epiphytes for decades
(Harmon et al. 1986). Although mistletoe brooms were considered a unique substrate exploitable
by birds, their general use was likely underestimated. For instance, if a bird gleaned a prey item
from Lobaria spp. located on a mistletoe broom formation, the recorded substrate was foliose
lichen, and not the latter “mistletoe broom”. Since many epiphyte substrates are sympatric with
mistletoe brooms, the use of mistletoe broom as a contributing factor was probably
underestimated. Non-epiphytic/phorophytic resources included abiotic substrates such as air and
ground, and biotic substrates terrestrial herbs and mosses.
Foraging bouts were defined as any bird maneuvers or activities spent searching for,
procuring and/or handling food (Post and Götmark 2006). The only exception to this definition
of bout was for members of the aerial insectivore foraging guild (e.g., Tyrannidae) where only
food removal from a given substrate was considered a foraging bout: determination of a specific
foraging substrate inspected by flycatchers from a perch site could not be determined. A trial
18
period was conducted to train and minimize variation between individual observers. A laser
range finder was used to ensure that ocular height estimates were reliable and within 10% of true
height. The major difference between Walking Transects and Tree Plots data collection protocols
was that multiple observations of conspecific foraging individuals (to ensure observations were
independent) could be avoided in the Walking Transects but not in the Tree Plots.
Observations were recorded using digital voice recorders and transcribed to an MS
Access Database from tape playback in real time. The original voice-recorded observation data
were archived in digital files.
Resource Availability
Bird selection and proportional use of epiphytic and host tree resources were analyzed by
comparing epiphytic and host tree attributes with resource and tree species availability.
Quantifying epiphyte availability is important because most surfaces in old-growth forests are
covered by epiphytes. Therefore, bird use of epiphytes may reflect opportunism rather than
specialization (Sillett 1994). Relative availability of intra-epiphytic groups was determined from
biomass estimates derived from vertical transects in a 2.3 ha plot located within the southwestern
portion of the RNA study area (McCune 1993, McCune et al. 1997, Harmon et al. 2004). The 2.3
ha plot comprises the Wind River Canopy Crane Research Facility (Franklin and DeBell 1988,
Shaw et al. 2004). Although bryophyte biomass data were lacking in the 2.3 ha plot (McCune et
al. 1997), Harmon et al. (2004) estimated bryophyte biomass to be equivalent to cumulative
lichen biomass, because bryophytes and lichen were equally abundant. The relative proportion of
each epiphyte group was calculated by dividing the biomass estimate of each group by the total
(Table 4). For instance, alectorioid lichen biomass was 934 kg ha-1 or 14% of the total combined
epiphyte group biomass. Cyanolichen & other lichen comprised 36% of total epiphyte biomass,
and bryophytes comprised 50% (Table 4).
19
Table 4: Estimated biomass, relative proportion and ratio of epiphyte groups (source: McCune
1997 unless otherwise specified).
Relative
Epiphyte group
Estimate kg ha-1
Proportion
Alectorioid lichens
934
0.14
Cyanolichens and Other lichens
2382
0.36
Bryophytes* (2x lichen biomass)
3316
0.50
Total
6632
1.00
* Harmon et al. (2004)
Estimated stores of carbon associated with live biomass as measured by Harmon et al.
(2004) were used to calculate relative resource availability for stem bark, live and dead branches,
foliage, understory vegetation, and total epiphytes (Table 5). The relative proportion of each
major resource pool was calculated by dividing the biomass estimate of each respective available
resource pool by the total resource pool carbon store (9,405 g C m-2). For instance, foliage
biomass was 941 g C m-1 or 10% of the total available resource pool. Following, total epiphyte
biomass was 100 g C m-2 or 1% of the total available resource pool.
Table 5: Estimated stores of carbon from the Canopy Crane Plot (Harmon et al. 2004).
Major Resource Pool
Stem bark
Branches (live and dead)
Tree foliage
Understory shrubs and herbs
Epiphytes
Total
Store (g C m-2)
3,337
4,807
941
220
100
9,405
Relative
Proportion
0.35
0.51
0.10
0.02
0.01
1.00
I used tree data from permanent monitoring plots in the TT Munger RNA (Meyers and
Fredricks 1993) to calculate relative availability of individual tree species, and compare against
the observed frequency of tree selection by birds. The data from each of the 20 respective Tree
Plots and all permanent monitoring plots located within 400 m of the Walking Transect were
averaged to calculate relative tree availability for five trees in the pooled analysis (Table 6). The
category “Others” included T. brevifolia, Cornus nuttallii and vertical snags. Understory shrubs,
herbs and logs were not included in the analysis. For the comparison between survey sampling
procedures (Tree Plots versus Walking Transect), relative tree availability were calculated
separately.
20
Table 6: Relative availability of tree species (Data were provided by the Permanent Study
Plot program, a partnership between the H. J. Andrews Long-Term Ecological Research
program and the U.S. Forest Service Pacific Northwest Research Station, Corvallis, OR.).
Tree species
Pseudotsuga menziesii
Tsuga heterophylla
Abies spp.
Thuja plicata
Others
Total
No. Trees
66
227
57
12
35
9,405
Relative
Proportion
0.17
0.57
0.14
0.03
0.09
1.00
Point Counts
Although point counts may result in an upward bias of density estimates (Buckland
2006), extensive point counts are an efficient and data rich census method for bird populations in
forested and difficult terrain (Ralph et al. 1993). Standard 10-minute variable circular plot (VCP)
point counts (Reynolds et al. 1980, Ralph and Michael 1981) provided an estimate of numbers of
species and individuals present. One point count station was established in each of the Tree Plots
and each station was located a minimum of 400 m apart and was visited once, for a total of 20
sites. Point counts began after a five-minute quiet period after the canopy-level observer climbed
the tree and assumed his position on the tree seat. The two observers (upper canopy-level
observer and ground-level observer) conducted the point counts simultaneously. Because of
logistic constraints, the point counts at the canopy-level were performed by one person.
Similarly, all ground-level point counts were performed by another individual observer.
Observers participated in a week-long trial period to train and minimize variation between
individual observers, and a laser range finder was used to ensure that distance estimates were
reliable. The abilities of observers to identify birds by both sight and sound and estimate
horizontal distances were tested.
All birds detected during the counts were recorded, and the distance from the observer to
each individual detected was estimated to the nearest meter. Distances were collected to assess
differences in counts recorded in three distance bands: 30 m, 75 m, and unlimited plots. No
attempt was made to calculate individual species densities because only one point was sampled
each day (Buckland 1993, Bibby et al. 1992). Rather, detection differences in relative
abundances and species richness were assessed among the three distance bands between
observers. Birds were identified by sight and vocalization. The location of the “first” detection
of an individual was recorded, even if the individual moved closer during the count. For the point
21
counts, coarse scale habitat variables such as tree species availability were assessed using
methods of Ralph et al. (1993). Canopy cover was calculated from the ground-level with a
spherical convex densiometer (Lemmon 1956): nine samples were taken within the 30 m-radius
plots. Point counts were conducted between 07:00 and 09:00, and all bird species were recorded
to generate a master species list (Appendix C).
Statistical Analysis
Sequential foraging data were collected for each individual bird observed until the
individual disappeared from sight. However, data analyses were performed for only the first
foraging bout and/or searching activity, to avoid problems with independence (Hejl et al. 1990).
Nine foraging guild categories were defined by substrate exploited, following Manuwal (1991):
1) aerial insectivores (AI), 2) bark insectivores (BI), 3) aerial predators (H), 4) low understory
herbivore/insectivores (LUHI), 5) nectarivores (N), 6) omnivore scavengers (OS), 7) timberfoliage insectivores (TFI), 8) timber-foliage insectivore/omnivores (TFIO), and 9) timber seed
eaters (TS). The H and TFIO foraging guilds, and one TS member (Band-tailed Pigeon) were
excluded from the statistical analyses.
Foraging bouts for each species and/or foraging guild were quantified as a percentage of
the total foraging bouts (frequency). Frequency distributions and descriptive statistics were
computed to assess:
1. Number of species and foraging guilds that used epiphyte groups,
2. Frequency of substrate used by species, foraging guilds and all observations,
3. Proportion of total foraging bouts that involved epiphyte resources, relative to phorophyte
resources, by tree species, tree class, horizontal and vertical crown zone, bird position in
the tree, foraging height, foraging posture, foraging behavior, and tree status.
All Tree Plot and Walking Transect data were pooled for an overall analysis, but were also
analyzed separately, to compare survey procedures.
Resource Availability and Use: The log-likelihood ratio test (G-test for independence
with the William’s correction factor) was used to compare substrate selection and substrate
availability among epiphyte and phorophyte substrates (Sokal and Rohlf 1995). The G-test was
also used to determine whether species use of epiphytic groups and tree species were in
proportion to their availability. Proportional use of epiphyte and host resources, relative to
22
availability, was compared among survey procedure for five common species (e.g., Brown
Creeper, Chestnut-backed Chickadee, Hairy Woodpecker, Gray Jay, and Red-breasted Nuthatch).
In addition to a pooled analysis for the five species, I used log-likelihood ratio tests for each of
the five species for a comparison between survey procedures. Expected frequencies were based
on hypotheses extrinsic to the data (McCune et al.1997 for epiphytic group availability, and
Harmon et al. 2004 for tree species). The following rule for the G-stat test was employed: no
expected frequency should be less than 5.0. For expected frequencies less than 5.0, classes were
pooled. Data analysis was performed using Microsoft Access and Excel (Keller 2001).
Epiphyte Specialization: Epiphyte users were considered specialists (species whose
foraging activities involved epiphytic resources >75% of their total foraging bouts), regulars users
(between 25 - 75 %), or occasional users/generalists (less than 25%) (Remsen and Parker 1984).
Only species with a minimum sample size ≥ 10 total foraging bouts were assigned a degree of
specialization (Remsen and Parker 1984).
Community Structure: Nonmetric multidimensional scaling (NMS) was performed to
graphically represent the differences (and similarities) in epiphyte-related foraging strategies and
extract meaningful gradients about the community structure of foraging guilds and species. NMS
is an ordination procedure that provides insight into a high-dimensional space by seeking and
displaying the strongest structure. NMS uses ranked distances (similarities and dissimilarities) to
summarize the relationship among samples (McCune and Grace 2002). The NMS of the pooled
Tree Plot and Walking Transect epiphyte foraging data was a niche-space analysis of
guilds/species (objects) and the epiphyte resources they used (attributes). The distances between
the points on the ordination approximate dissimilarity in foraging strategies and foraging
locations, and thus provide a visual tool for examining the multiple interrelated foraging location
and behavior factors, and insight into interactions among species and guilds. Two categorical
foraging behaviors (foraging posture, foraging maneuver), seven environmental attributes (crown
class, vertical and horizontal crown position, tree species, tree condition, substrate and tree
position) and one quantitative variable (bird height) compared among guild and species use of
epiphyte resources. The TFIO foraging guild and 16 outliers were excluded from the NMS
analysis, due to insufficient sample sizes, and results of an outlier analysis. With the exception of
the quantitative variable foraging height, all raw categorical data were ordinated for the NMS.
Monte Carlo procedures (randomization tests) were conducted to assess whether the amount of
variation described by the different axes was more or less than expected by chance. The
23
Sørensen (Bray and Curtis) similarity measure was used for calculating the similarity matrix.
Random starting configurations were used for the ‘autopilot (slow and thorough)’ mode, 3-D
solution of 250 runs with real data and random data, with 500 iterations. Stability was examined
by analyzing a plot of stress versus iteration (stress value in relation to dimensionality). Stress is
defined as a measure of lack of fit, or departure from monotonicity in the relationship between the
dissimilarity of the original matrix and the new 3-D configuration/solution (McCune and Grace
2002). Correlation coefficients enabled a comparison of sample positions on the ordination with
guild foraging strategies, and foraging location variables. The correlation coefficients express
linear (Pearson’s r) and rank (Kendall’s Tau) relationships between the ordination scores and
foraging height.
I used Multi-Response Permutation Procedures (MRPP) to test the null hypothesis of no
difference between groups (e.g., foraging guilds in the Tree Plots and Walking Transects). MRPP
is an analysis of similarity and does not require distributional assumptions (Mielke 1984, Mielke
and Berry 2001). The MRPP analysis measured how similar foraging strategies were within a
group, compared to similarities among groups. Among-group dissimilarity and within-group
similarity occurs when groups chance-corrected within-group agreement values (A values)
exceed 0.1. Among-group similarity is evident with groups whose A values are <0.1, which
indicates broad overlapping, and among-group similarity. MRPPs were conducted on all pooled
epiphyte foraging events using: 1) the four epiphyte functional group categorical variables
(alectorioids, bryophytes, and cyanolichens & other lichens, and lichen/bryophyte admixture,
hereafter referred to as “epiphyte functional groups”), and 2) eight finer scale categorical
variables denoting specific epiphyte substrates (alectorioid lichen, foliose lichen, fruticose lichen,
fruticose and foliose lichen, pendant bryophyte, appressed bryophyte, other lichen, and bryophyte
and lichen; hereafter referred to as “finer scale epiphyte substrates”). I ran MRPP pairwise
comparisons on the finer scale epiphyte substrate variables to measure differences within and
among foraging behaviors and environmental attributes (e.g., pendant vs. appressed bryophyte).
NMS and MRPP were performed with PC-ORD, version 5 (MjM Software Design, Gleneden
Beach, Oregon, Kruskal 1964a, 1964b, Mather 1976).
Point Counts: I performed Paired Student t-tests ( = 0.05) to compare detection
frequencies, species richness and relative abundance between observer location, and among
distance bands: 30 m, 75 m, and unlimited, and a two-factor analysis of variance (ANOVA) with
replication to compare detection frequencies and relative abundance between point count stations
among distance bands and between observers for nine core species (e.g., Brown Creeper,
24
Chestnut-backed Chickadee, Golden-crowned Kinglet, Gray Jay, Hermit Thrush, Hermit Warbler,
Pacific-slope Flycatcher, Red-breasted Nuthatch and Winter Wren). I used the Wilcoxon Rank
Sum test to compare the rank order of species relative abundance in the unlimited-radius plots
between canopy- and ground-level observers, and the Wilcoxon Signed Rank Sum test to
compare the rank order of species abundances in my 75 m radius plots with mesic old-growth
forest bird abundances in Manuwal (1991). The Student t-tests, ANOVA and Rank Sum tests
were performed with Excel. Because there is a dependence in counts based on subsequent
increases of distance bands from a common point (i.e., the samples are not independent), the
significance of the ANOVA and t-test may be liberal (Thompson and Schwalbach 1995).
Shannon’s species diversity indices were generated with PC-ORD, version 5 (MjM
Software Design, Gleneden Beach, Oregon, Kruskal 1964a, 1964b, Mather 1976). Although no
attempt was made to calculate relative species densities or detection probabilities (Reynolds et al.
1980, Buckland et al. 1993), I compared the relative distribution of detection distances between
observers for the nine core species. Calculations of densities would be imprudent because my
point count methodology violated an important assumption of density measures: a multi-point
count station survey assumes that bird detections in each plot are independent and the same birds
are not recounted from station to station. However, since only one survey per day was conducted,
birds could perceivably move from one station to another (despite a minimum distance of 400 m
from each other), resulting in both population and density overestimates.
25
CHAPTER 4
RESULTS
This chapter is divided into five sections. In Section 1, I summarize results of the
foraging observations and address whether any species are epiphyte specialists. Sections 2
through 4 report the results of spatial and substrate specialization (Section 2), use of resources in
relation to availability (Section 3), and community structure and composition (Section 4). In
Section 5, I compare the two sampling procedures (Subsection 1) and results of the simultaneous
canopy- and ground-level variable circular plot point counts (Subsection 2).
Section 1
Bird Use of Epiphytes
A total of 71 bird species, representing 30 families, were detected during the surveys
(Appendix C). Five families were well represented: the Tyrannidae (5 species), Parullidae (5
species), Hirundinidae (6 species), Emberizidae (7 species), and Fringillidae (6 species).
Cumulatively for both sampling procedures (Walking Transects and Tree Plots), foraging data for
735 individuals were captured, representing 2,902 sequences from 29 species, 20 families and 9
foraging guilds. The majority of foraging data (85%) were contributed by 8 species (Table 7).
The Chestnut-backed Chickadee was the most frequently detected species, followed by Gray Jay,
Winter Wren, Red-breasted Nuthatch, Brown Creeper, Pacific-slope Flycatcher, Red Crossbill,
and Dark-eyed Junco. Of the 735 bird observations from 29 species, 722 foraging bouts from 22
species were used for assessing relative resource use (Table 7).
Of all 722 foraging observations, 28.7% (207) involved epiphyte substrates (Table 8).
Bryophytes were the most frequently used epiphyte group (44% of all epiphyte foraging bouts),
followed by “cyanolichens and other lichens” (41%), and alectorioid lichens (13%). Pendant
bryophytes were the most common finer-scale epiphyte substrate used, followed by foliose
lichen, then appressed bryophytes. Approximately 20% of all bouts on bryophytes involved the
cattail moss, Isothecium myosuroides. Foliose lichens were the most frequently exploited lichen
substrate, accounting for over half of the bouts (48 of 85 records) on all lichen substrates.
Foraging bouts on alectorioid lichens exclusively comprised less than 4% of all observations,
26
although an additional 11 foraging bouts involved an admixture of alectorioid lichens and
bryophyte/other lichens. More than 60% of the total bouts occurred on resources provided by the
host (Table 8); live foliage comprised most of the phorophyte records (183 of 468 records or
25%); bark substrates were used in 23% of all observations.
Table 7: Total species observation time (s), number of foraging observations (n, number of
individuals) and sequences (Tree Plot and Walking Transect data pooled).
English Name
Band-tailed Pigeon*
Barred Owl*
Black-headed Grosbeak*
Brown Creeper
Chestnut-backed Chickadee
Common Nighthawk*
Dark-eyed Junco
Golden-crowned Kinglet
Gray Jay
Hairy Woodpecker
Hammond's Flycatcher
Hermit Thrush
Hermit Warbler
Northern Flicker
Northern Pygmy-Owl*
Pacific-slope Flycatcher
Pileated Woodpecker
Pine Siskin
Red Crossbill
Red-breasted Nuthatch
Red-breasted Sapsucker
Rufous Hummingbird
Steller’s Jay
Turkey Vulture*
Varied Thrush
Vaux’s Swift*
Western Tanager
Wilson’s Warbler
Winter Wren
Foraging
Guild1
Time
n
seq.
TS
H
TFIO
BI
TFI
AI
LUHI
TFI
OS
BI
AI
LUHI
TFI
BI
H
AI
BI
TS
TS
BI
BI
N
OS
H
LUHI
AI
TFI
LUHI
LUHI
TOTAL
2
250
3
1416
4412
2
1310
529
4774
3378
17
798
50
45
117
1181
69
16
1473
2825
42
380
601
40
24
85
167
1
5146
29153
1
2
1
51
167
1
22
21
108
43
3
18
2
1
1
46
2
2
43
60
1
21
7
1
2
5
3
1
99
735
1
2
1
186
574
1
137
86
427
254
4
83
10
1
5
114
9
2
64
317
8
37
49
1
4
7
16
1
501
2902
1
Foraging guild codes: AI = aerial insectivore, BI = bark insectivore, LUHI= low-understory herbivore/insectivore, N
= nectarivore, OS = omnivore scavenger, TS = timber seed-eater, TFI = timber foliage insectivore, TFIO = timber
foliage insectivore/omnivore, H = aerial predator (catch non-insectivorous prey); * excluded from statistical analysis
27
When Tree Plot and Walking Transect data were pooled, four foraging guilds comprised
83% of the foraging data, namely low-understory herbivore/insectivores (LUHI), bark
insectivores (BI), timber foliage insectivores (TFI), and omnivore-scavenger (OS) foraging guilds
(Table 7, Figs. 4 and 5). All seven foraging guilds used epiphytes. BI used lichen and bryophyte
substrates more frequently than any of the other foraging guilds, accounting for 37% of the
foraging guild’s records. BI used pendant bryophytes and foliose lichen substrates more often
than other epiphytic substrates, although alectorioid lichens and appressed bryophytes located on
the tree boles were also important foraging substrates. Epiphytic resources were also important
foraging locations for OS (35% of their foraging bouts) and LUHI (32%, Fig. 4). OS used
pendant bryophytes, foliose lichens and alectorioid lichens in almost equal proportions (Fig. 5).
Observations comprising the OS foraging guild reflected foraging bouts weighed heavily by the
corvid, Gray Jay (45 of 48, 94%); the other sympatric corvid, Steller’s Jay, comprised the
remaining OS foraging bouts (Table 7). Appressed and pendant bryophytes accounted for over
75% of the foraging bouts of epiphytic substrates by LUHI (Fig. 5). Observations of Winter
Wren comprised 68% of the sample data to the LUHI foraging guild, followed by Dark-eyed
Junco (Table 8). TFI foraged primarily amongst live foliage, although 27% of their foraging
bouts involved epiphytic resources. A third of all TFI epiphyte-related foraging bouts occurred
on foliose lichen, and more than 15% of their bouts occurred on pendant bryophytes, fruticose
and alectorioid lichens (Fig. 5). Nectarivores (N), aerial insectivores (AI), and timber-seed eaters
(TS) used epiphytes less frequently than the other foraging guilds; approximately 10% of N, AI
and TS foraging bouts occurred on epiphytes.
Fourteen species of birds used epiphyte substrates whereas phorophyte resources
provided foraging substrates for an additional seven species (21 species). All fourteen bird
species used lichen substrates when all lichen substrates were pooled (e.g., alectorioid,
cyanolichen and other lichens), whereas three fewer species used bryophytes. Although 11
species used bryophytes, four species accounted for 79% of these data: Winter Wren (33 records),
Brown Creeper (13 records), Chestnut-backed Chickadee (13 records), and Gray Jay (14 records).
Fewer bird species used alectorioid lichens than the other epiphyte groups, and 77% of the
foraging bouts on alectorioid lichens were done by three species: Gray Jay, Chestnut-backed
Chickadee, and Brown Creeper.
Chestnut-backed Chickadees and Red-breasted Nuthatches comprised approximately
50% of the “cyanolichen and other lichens” foraging records. The 18 records involving an
“admixture of foliose and fruticose lichen” included activities by seven bird species on dense,
tangled mixtures of both epiphyte forms. Of the 18 “admixture of foliose and fruticose lichen”
28
records, seven records were bouts by Chestnut-backed Chickadee: six of the seven records were
alectorioid lichen twisted around foliose forms (Lobaria spp. and Platismatia spp.). Four of the
18 records involved mistletoe broom formations on T. heterophylla. A Pacific-slope Flycatcher,
two Chestnut-backed Chickadees and one Hairy Woodpecker used an admixture of
“lichen/bryophyte”. Only a small proportion of the records (8 bouts) involved exclusive use of T.
heterophylla mistletoe brooms.
Table 8: Number of species, foraging guilds, and individuals (% of all substrates) that used
epiphyte, phorophyte and other substrates (Tree Plot and Walking Transect data pooled).
Epiphyte
Substrate
Alectorioid lichen
Cyanolichen and other lichen
Foliose lichen
Fruticose lichen
Other lichen
Admixture (fruticose & foliose)
All cyanolichen and other lichen
Bryophytes
Pendant bryophyte
Appressed bryophyte
All bryophytes
Admixture (lichen & bryophyte)
Other
Phorophyte
Epiphyte Total
Foliage (live and dead foliage)
Bark
Dead wood (includes rootwads)
Cone
Other (flower)
Mistletoe brooms
Phorophyte Total
Air
Perched litter
Ground
Terrestrial herbs/mosses
Other
Other Total
All Substrates Total
No. species
No. guilds
No. individuals
8
6
26
9
2
8
7
12
5
2
5
7
6
48
5
14
18
85
10
7
6
3
53
39
11
3
6
3
92
4
14
18
17
11
1
1
3
21
5
4
4
4
1
10
22
7
7
7
6
1
1
3
7
4
4
2
2
1
7
7
207 (28.7%)
183
166
73
30
8
8
468 (64.8%)
16
4
16
10
1
47 (6.5%)
722 (100.0%)
29
Epiphyte
1.0
(158)
(115)
BI
OS
Host
(142)
Mistletoe
Other
(192)
(21)
(49)
(45)
TFI
N
AI
TS
Frequency of Use (%)
0.8
0.6
0.4
0.2
0.0
LUHI
Figure 4: Major resource allocation for seven avian foraging guilds (n = total number of
foraging bouts); Tree Plot and Walking Transect data pooled; foraging guild codes: AI = aerial
insectivores, BI = bark insectivores, LUHI= low-understory herbivore/insectivores, N =
nectarivores, OS = omnivore scavengers, TFI = timber foliage insectivores, TS = timber seedeaters).
1.0
(59)
(40)
(46)
(51)
Pendant bryophyte &
Foliose lichen
Appressed bryophyte
Frequency of use (%)
0.8
Pendant bryophyte
0.6
Foliose & Fruticose
lichen
Other lichen
0.4
Fruticose lichen
0.2
Foliose lichen
0.0
BI
OS
LUHI
TFI
Alectorioid lichen
Figure 5: Epiphytic group allocation for four avian foraging guilds (n = total number of foraging
bouts, Tree Plot and Walking Transect data pooled; foraging guild codes: BI = bark insectivores,
LUHI= low-understory herbivore/insectivores, OS = omnivore scavengers, TFI = timber foliage
insectivores).
30
Epiphyte Specialization
No species or foraging guild was an epiphyte specialist. Seven species were regular users
of epiphytes, and five species were occasional users/generalists (Table 9). The BI, Brown
Creeper, used epiphyte substrates during 53% its foraging bouts, more frequently than the other
regular users of epiphytes. The LUHI, Winter Wren, used epiphytes during 47% if it’s foraging
bouts, and approximately one third of all foraging bouts by Red-breasted Nuthatch, Gray Jay and
Chestnut-backed Chickadee involved epiphytes.
Alectorioid lichens were used by four regular epiphyte users (Brown Creeper, Gray Jay,
Chestnut-backed Chickadee, and Red-breasted Nuthatch) and three occasional users (Dark-eyed
Junco, Red Crossbill, and Rufous Hummingbird), although less than 10% of their bouts involved
the pendant fruticose lichen. Five of the 12 regular and occasional users did not use alectorioid
lichens as a foraging substrate. Brown Creepers and Gray Jays used alectorioid lichens slightly
more often, relative to the other 12 species.
Three regular epiphyte users (Brown Creeper, Hermit Thrush and Winter Wren) used
bryophyte substrates during more than 20% of their foraging bouts, which accounted for the
lower mean height of their epiphyte-related foraging activities, relative to the other regular users.
Although Gray Jay and Hairy Woodpecker used bryophytes during more than 10% of their bouts,
both species also foraged in the upper canopy (e.g., at 60 m). Bryophytes were used by all
occasional users except Golden-crowned Kinglet and Red Crossbill. Cyanolichens and other
lichens were used more frequently by Red-breasted Nuthatch, Brown Creeper and Chestnutbacked Chickadee, although all regular users used these groups of epiphytic lichens. The Rufous
Hummingbird did not use cyanolichens and other lichens as a foraging substrate, but searched
alectorioid lichens more frequently than the other occasional users.
In general, the foraging behaviors used most frequently by regular users of epiphytes
were hanging, perching, and hopping while searching, and glean or pecking food items (see
Section 2 for an analysis of foraging behaviors of all observations). Members of the BI foraging
guild (e.g., Brown Creeper and Hairy Woodpecker) used epiphytes primarily by hanging
vertically or upside-down while probing, hammering/pecking or inspecting cyanolichen and other
lichen (primarily bark lichen and prostrate mosses on the bole, e.g., Hypnum spp.). Red-breasted
Nuthatches foraged slightly higher in the canopy than Chestnut-backed Chickadee when using
epiphytic substrates, relative to host resources, and both species used “cyanolichen and other
lichen” substrates regularly. Chestnut-backed Chickadees foraged with hops and short flights
across splays of foliage and branchlets to pause momentarily, hang and glean food items from
31
both phorophyte and epiphyte substrates. Gray Jays used bryophytes and cyanolichen and other
lichens in equal proportions, and used a variety of postures: searching while perched, hanging
vertically, reaching under, or hanging upside-down. Gray Jays obtained food items from
epiphytes with gleaning, pecking/probing, pulling and hammering maneuvers. The hover-glean
activities of the Pacific-slope Flycatcher occurred below and in the lower canopy, at mean heights
of 14 m (host resources) and 15 m (bark lichen on the bole, and pendant bryophytes on dead
branches). Comparatively, the 12 Pacific-slope Flycatcher aerial sallies and sorties (where flying
insects were captured on the wing) took place at a mean height of 16 m.
Discussion
Differences in foraging strategies reflect the restrictions imposed upon the foraging bird
by foraging substrates as well as the morphological characteristics of the birds themselves
(Robinson and Holmes 1982). Similarly, the foraging strategies required to exploit epiphytes are
restricted by the physiological constraints of the respective epiphyte substrates, which has been
shown in tropical forests (Sillett 1994). In addition, the vertical zones (heights) of epiphyte
foraging substrates reflect the vertical stratification of epiphyte communities (McCune et al.
2007), which could influence the vertical distribution of bird communities in coniferous forests
(Shaw 2004, Shaw et al. 2002). The species and foraging guilds documented during the Tree
Plots and Walking Transects are congruent with species abundance reported for the area (Shaw et
al. 2002). Not all bird species and foraging guilds used epiphytes in similar proportions or with
similar foraging strategies.
Although I found no specific epiphyte group specialists, all epiphytic lichens and
bryophytes were used as foraging substrates. How the presence or absence of the epiphyte groups
influences the foraging strategies of the bird communities cannot be ascertained with these data.
However, epiphytic lichens have been positively correlated with increased avian species richness
in boreal forests (Pettersson et al. 1995, Uliczka 1999). Similarly, experimental manipulation has
shown that the complete removal of epiphytes in a tropical forest negatively influenced some bird
communities (Cruz-Angon et al. 2008). Further research is needed to determine whether or how
alteration of temperate coniferous forest epiphytes would influence avian communities or
foraging strategies.
32
Table 9: Percent total foraging, postures, maneuvers and foraging height (m) of 12 bird species searching epiphyte functional groups, relative to
all foraging bouts, Tree Plots and Walking Transects data pooled.
Bryophytes
Epiphyte
Foraging
Posture1
Epiphyte
Foraging
Maneuver2
Epiphyte
Foraging
Height (mean,
range)
Foraging Height
of Non-Epiphytes
(mean, range)
19.6
25.5
HA, HG/PE
S, PK, PR, GL, PL
11.6 (1-32)
16.4 (1-41)
4.8
18.0
7.8
HA, PE, HP, HG,
LE, SF,HO
S, GL, PK, PR, PL
23.1 (1.5-55)
19.7 (0.5-55)
7.4
13.0
13.0
PE, HA, RU
LE/HG/RU
S, PK/GL,
PR, PL, HA
21.5 (2-50)
26.3 (0-60)
Hairy Woodpecker (43)
0
9.5
19.0
HA, PE, HG
HA, PK, S
16.6 (1.5-40)
21.8 (2-60)
Hermit Thrush (18)
0
5.6
22.2
PE, LE, AM
S, PK
1.3 (0-2)
2.5 (0.5-5)
3.3
23.3
3.3
HA, PE, HG, HP
S, PK, PR, HA
34.2 (3-60)
34.3 (11-60)
0
14.1
33.3
HP, PE, HA/SD,
RP, LE, AM, HO
PK, S, GL, PR
1.4 (0-8)
1.1 (0-10)
0
9.5
0
PE
S
12.0 (6-18)
17.9 (6-36)
4.5
4.5
9.1
LE/PE/RU/SD
PK, GL/S
11.2 (0.75-23)
1.3 (0-5)
0
6.5
6.5
HO, PE
GL, S
15.2 (6-27)
14 (0-40)
Red Crossbill (43)
2.3
7.0
0
PE
S, PK/PR
45 (45-50)
43.9 (27-60)
Rufous Hummingbird (21)
4.8
0
4.8
HO
S
11.8 (5.5-18)
5.6 (0.5-40)
Alectorioid
Lichens
Cyanolichens
and Other
Lichens
Brown Creeper (51)
7.8
Chestnut backed Chickadee (167)
Gray Jay (108)
English Name
(n, total observations)
REGULAR USERS
Red-breasted Nuthatch (60)
Winter Wren (99)
OCCASIONAL USERS/GENERALISTS
Golden crowned Kinglet (21)
Dark-eyed Junco (22)
Pacific-slope Flycatcher (46)
1
Postures: HA = hang, PE = perch, HG = hang upside-down, HP = hop, RU = reach under, LE = lean into, RP = reach up, SF = short flight (within substrate), SD
= stand, AM = walk/run on ground, HO = hover; 2Maneuvers: S = search, PR = probe, HA = hammer, PK = peck, GL = glean, PL = pluck; foraging postures and
maneuvers listed in order of importance. Regular epiphyte users were those species whose foraging activities involved epiphytic resources between 25 - 75 % of
their total foraging bouts, and occasional users/generalists (less than 25%) (Remsen and Parker 1984).
33
Section 2
Spatial and Substrate Specialization
More than 30% and 50% of all bryophyte and lichen foraging bouts, respectively,
occurred on T. heterophylla. Approximately 80% of all foraging bouts on lichens occurred on P.
menziesii and T. heterophylla, and 62% of the bouts on these two tree species were birds using
foliose lichen, or an admixture of foliose and fruticose lichen (Table 10). Thuja plicata was
rarely used during bouts on epiphytes (Tables 10 and 11). See Section 3 for an analysis of tree
species use, relative to tree species availability.
Birds used all tree classes, and foraged throughout the vertical and horizontal crowns of
both live and dead trees during foraging bouts on epiphyte substrates (Table 12). Dominant and
suppressed trees comprised over 70% of all epiphytes foraging bouts, with 43% occurring in the
inner portion of the live crown and 63% occurring in the mid and lower vertical crown. In
general, the proportional use of tree classes during foraging bouts on epiphytes reflected the
proportions found for host substrates, with one exception: intermediate trees were selected
slightly more frequently during foraging bouts on host resources, attributed to foraging bouts on
foliage (21%) and conifer seed cones (31%). Overall epiphyte use was more frequent in the
inner- and mid-portion of the horizontal tree crown, relative to overall phorophyte use. Lichens
were used more frequently in larger trees whereas bryophytes were used more frequently in the
lower portion of the forest profile.
Birds concentrated foraging activities on alectorioid lichens in the outer, upper and mid
portions of the live crown on dominant and codominant P. menziesii and T. heterophylla (Tables
10 and 12). Almost 90% of the bouts involving alectorioid lichens occurred on P. menziesii and
T. heterophylla and more than half of the bouts occurred between 12 and 37 m while birds were
hanging, searching, pecking or probing the pendant lichens. Both small-bodied passerines
(including Chestnut-backed Chickadee, Brown Creeper, and Red-breasted Nuthatch) and a
medium-sized corvid (Gray Jay) were able to hang onto or hang nearby the pendant lichens to
procure or search for food items. Birds also used alectorioid lichens located on branches and the
bole in the inner portion of the crown, although less frequently. Members of the BI, OS, and TFI
foraging guilds used alectorioid lichens generally between 29 and 34 m, although bouts on
alectorioids ranged in height from 3 to 60 m (Tables 13 through 15).
34
Table 10: Number of foraging bouts on lichen substrates by tree species/types, Walking Transect
and Tree Plot data pooled.
Tree species/type
T. heterophylla
P. menziesii
Abies spp.
T. brevifolia
T. plicata
Pinus monticola
Log
Snag
Understory shrubs
Branches on ground
Total
1
AL
14
9
2
0
0
1
0
0
0
0
26
BL
4
4
2
0
0
0
1
2
0
1
14
Lichen type1
FR
3
1
0
0
1
0
0
0
0
0
5
FO
29
11
1
1
0
3
0
1
1
1
48
FR & FO
11
5
2
0
0
0
0
0
0
0
18
Total
61
30
7
1
1
4
1
3
1
2
111
Lichen types: AL = alectorioid, BL = bark lichen, FR = fruticose, FO = foliose.
Table 11: Number of foraging bouts on bryophyte substrates by tree species/vegetation type,
Walking Transect and Tree Plot data pooled.
Tree species/type
T. heterophylla
P. menziesii
Abies spp.
T. brevifolia
Acer circinatum
T. plicata
Logs
Snags
Branches on ground
Total
Bryophyte type
Pendant
Appressed
24
6
0
3
9
2
13
5
9
6
1
0
1
14
0
1
0
2
57
39
Total
30
3
11
18
15
1
15
1
2
96
Cyanolichens and other lichens were used throughout the horizontal profile of the tree
crown on branches in the mid- and lower-live crowns of dominant and codominant trees (Table
12). Birds used foliose lichens with the hanging posture, although less so than by the perched
position. The most frequent maneuvers used on foliose lichens included pecking, gleaning, and
probing behaviors, while hanging from or leaning into the thallus. Foraging strategies used on
Lobaria spp. included a variety of postures. For those bouts on L. oregana where food items
were actually procured (i.e., not searching), “hanging” and “leaning into” were the most frequent
postures used. Approximately half of the foraging activities on foliose, fruticose and bark lichens
occurred between 12-37 m and the remaining bouts were distributed equally between the high and
low height classes (Tables 13 and 15).
35
Foraging bouts on bryophytes occurred mostly in the inner, mid and lower portion of the
live crown on live branches and boles of suppressed T. heterophylla and Taxus brevifolia (Table
12). More than 84% of these bouts occurred below 12 m, and approximately 40% of the bouts
occurred on Acer circinatum, and appressed bryophytes on horizontal logs (Table 11). Species
that foraged in the mid to upper canopy, such as Chestnut-backed Chickadee and Red-breasted
Nuthatch, rarely foraged on bryophytes. Possible explanations for this is likely resource scarcity
rather than resource avoidance since the critical height limit for bryophytes is 28 m (McCune et
al. 1997) and the mean foraging heights of Chestnut-backed Chickadee (23 m) and Red-breasted
Nuthatch (34 m) were at or well above this limit. Aerial insectivores used bryophytes located
higher in the canopy, relative to the other foraging guilds (Table 14). During bouts on
bryophytes, birds primarily hung while searching, pecking or gleaning food items from pendant
and appressed mosses and liverworts (Table 12). For example, Hairy Woodpecker hung
vertically while searching and procuring stationary insects from within or behind appressed
bryophytes or beneath pendant bryophytes.
Chestnut-backed Chickadees and Red-breasted Nuthatches concentrated foraging
activities in the outer-portions of the mid- and lower-crown, when both host and epiphytic
substrates were used (Appendices D and E). Red-breasted Nuthatches used epiphytic substrates
more frequently in the outer zones, and less frequently in the middle and inner zones, and showed
a preference for dominant (58%) and co-dominant trees (42%) when foraging on epiphytic
substrates. Red-breasted Nuthatches were observed using intermediate trees when foraging on
host resources only (Appendix F). Gray Jays used epiphytes more frequently in the middle and
inner portions of the mid and lower canopy. Brown Creepers used tree classes more evenly than
any of the other species and used suppressed and co-dominant tree classes for the majority of
their epiphytic substrate foraging bouts. Brown Creepers used the lower crown or below the live
crown and the inner crown exclusively during foraging bouts on both epiphyte and phorophyte
substrates. Similarly, Hairy Woodpeckers concentrated activities in the inner crown when using
host resources, whereas all epiphyte-related bouts occurred in both the mid and inner portions of
the lower live crown. Host substrate use by Hairy Woodpeckers was distributed throughout all
vertical tree zones. Hairy Woodpeckers selected suppressed trees for more than half of their
foraging bouts, and were not observed on intermediate nor co-dominant trees when using
epiphytic substrates, whereas they used all tree classes when foraging on host resources. Red
Crossbills concentrated foraging activities in dominant trees (67%), in the outer foliage of the mid
canopy, while taking seed from T. heterophylla cones. Pacific-slope Flycatchers used
36
intermediate trees more often than suppressed and dominant classes and concentrated their
activities in the outer, lower portions of, and below the live tree crown.
Table 12: Number of foraging bouts on epiphyte and phorophyte groups by tree class, tree
status, tree position, crown zone, posture and maneuver; data pooled.
Epiphyte Group
Tree Class
Dominant
Codominant
Intermediate
Suppressed
Tree Status
Live
Dead
Tree Position
Bole
Branch
Branchlet
Foliage
Vertical Zone
Above
Upper
Middle
Lower
Below
Horizontal Zone
Outer
Middle
Inner
Posture
Hang
Hang upside-down
Hover
Perch
Other
Maneuver
Glean
Peck
Probe
Hammer
Search
Other
Phorophyte
Alectorioid
Lichens
Cyanolichens &
Other Lichens
Bryophytes
Foliage
Bark and
Branches
15
7
2
1
45
21
15
5
10
10
6
66
61
31
38
37
56
26
27
46
25
1
79
8
70
23
172
1
135
24
6
7
7
6
17
45
21
6
31
63
1
1
0
16
4
152
54
81
23
2
1
12
4
4
4
8
14
25
21
7
0
4
7
25
13
0
51
62
38
1
5
16
30
35
20
12
4
9
23
20
25
5
18
25
111
26
19
18
27
65
18
0
1
7
0
26
6
3
32
22
23
9
6
31
27
17
18
35
61
52
57
9
4
71
25
1
3
3
1
18
0
15
15
4
3
51
1
17
33
9
6
29
2
80
14
2
0
84
3
18
18
4
14
104
8
37
Table 13: Percentage of foraging bouts by substrate among three height classes.
Epiphyte
Phorophyte
Other
Substrate
High (>37 m)
Mid (12-37 m)
Low (≤12 m)
Alectorioid Lichen
34.6
53.8
11.5
Cyanolichens and Other Lichen
25.8
50.6
23.6
Bryophytes
1.0
14.6
84.4
All Epiphytes
15.6
34.6
49.8
Foliage
20.6
45.6
33.9
Bark and Branches
11.5
42.4
46.1
All Phorophyte
18.1
41.4
40.5
Mistletoe
37.5
50.0
12.5
0
25.5
74.5
16.4
38.5
45.1
Other
All Substrates
Table 14: Mean foraging height (m SE) and range (m) of bird foraging guilds by substrate.
Foraging
Guild
Epiphyte Group
Alectorioid
Lichens
Cyanolichens &
Other Lichens
11.3 2.7
(6-15)
Phorophyte
Bryophytes
Foliage
16.0 6.1
(6-27)
15.9 2.4
(3-41)
Bark and
Branches
15.0 2.9
(1.5-40)
AI
---
BI
29.0 7.9
(7-60)
26.7 2.7
(1-60)
9.2 1.5
(1-32)
35.1 4.1
(6-55)
24.0 1.7
(1-60)
23.0
5.0 2.9
(0.2-18)
1.3 0.2
(0-5)
3.5 1.7
(0-37)
1.2 1.1
(0-5)
5.5
5.2 2.5
(1-15)
19.3 11.1
(2-40)
LUHI
N
18.0
---
OS
34.0 4.3
(12-50)
28.3 3.9
(3-50)
8.9 2.4
(2-40)
31.8 2.5
(6-60)
22.0 2.9
(0-55)
TFI
29.3 5.6
(3-55)
25.9 2.1
(6-45)
8.6 1.2
(1.5-15)
22.0 1.5
(0.5-55)
17.2 1.8
(1-45)
40.0
46.7 3.3
(40-50)
---
51.6 3.8
(32-60)
60.0
TS
38
Table 15: Mean foraging height (m SE) and range (m) of all bird by finer-scale substrates.
Substrate
Alectorioid lichen
Height
30.4 3.0 (3-60)
Epiphyte
Cyanolichen and other lichen
Foliose lichen
27.5 2.2 (0.2-60)
Fruticose lichen
20.4 3.2 (12-30)
Other lichen
20.3 3.7 (1-46)
Admixture (fruticose & foliose)
31.6 2.5 (9-46)
All cyanolichen and other lichen
Bryophyte
Pendant bryophyte
Phorophyte
Appressed bryophyte
Other
26.1 1.6 (0.2-60)
7.3 1.0 (0.1-40)
3.9 1.0 (0-32)
All bryophytes
5.9 0.8 (0-40)
Admixture (lichen & bryophyte)
10.0 1.9 (6-15)
All Epiphyte Substrates
17.4 1.1 (0-60)
Foliage (live and dead foliage)
23.0 1.3 (0-60)
Bark
17.4 1.1 (0-60)
Dead wood (includes rootwads)
16.9 2.2 (0-60)
Cone
41.1 2.0 (27-58)
Other (flower)
2.2 1.3 (0.5-11)
Mistletoe brooms
32.9 5.0 (7-55)
All Phorophyte Substrates
21.1 0.8 (0-60)
Air
14.4 2.4 (1-37)
Perched litter
14.9 8.0 (0.75-33)
Terrestrial herbs/mosses
0.02 0.01 (0-0.02)
All Other Substrates
All Substrates Total
6.0 1.4 (0-37)
19.0 0.6 (0-60)
39
Discussion
Red-breasted Nuthatches, Chestnut-backed Chickadees and Gray Jays were the most
commonly encountered birds and foraging strategies differed from those reported in the literature.
For example, foraging observations differed from the findings of Lundquist and Manuwal (1990),
in which Red-breasted Nuthatches were reported using horizontal tree zones equally in the spring.
Conversely, I found Red-breasted Nuthatches using the outer-, then the mid-horizontal zones
more often than the inner zone during that season. Red-breasted Nuthatches shifted foraging
activities to the mid- and upper-crown in spring (Lundquist and Manuwal 1990), which was
consistent with this study. However, in their study, no differentiation was made between host or
epiphyte substrates exploited in the vertical and horizontal zones. My study showed that Redbreasted Nuthatches used epiphyte substrates more often in the mid canopy (vertical), relative to
foraging bouts on host substrates. Similarly, my canopy-level observations showed Chestnutbacked Chickadees using the mid-vertical and outer-horizontal zones more often when both
phorophyte and epiphyte substrates were used, whereas Lundquist and Manuwal (1990) reported
Chestnut-backed Chickadees using the lower-vertical and mid-horizontal crown in spring.
Explanations for the discrepancy are unknown; although observer location might be an
important factor as all their observations were ground-based. In addition, their study had
substantially higher sample sizes than mine, and their study sites included both old-growth and
second-growth forest stands, which also might be contributing factors. Second-growth forests do
not contain refugia for as many organisms as do old-growth stands (Lindenmayer and Franklin
2002), which may influence foraging patterns (Weikel and Hayes 1999). Species richness and
biomass of all epiphyte groups is greatest in old-growth forests (McCune 1993). Accordingly, the
frequent use of lichen substrates by Gray Jays in this study may be partially explained by their
generalistic foraging nature and their proclivity to cache food for the winter by placing the sticky
mucilaginous stored food item behind flaking lichen, or covering the cache with pieces of lichen
(Strickland and Ouellet 1993). Similarly, the relatively high use of bryophytes and lichens by
Red-breasted Nuthatches may be explained by their caching behavior of storing invertebrates,
nuts and seeds, and concealing their caches, located under bark and beneath branches, with pieces
of bark, lichens, mosses and snow (Ghalambor et al. 1999). For both species, epiphyte use is
likely to remain the same or increase slightly in the fall and winter, because Gray Jays cache food
throughout the year, whereas Red-breasted Nuthatches cache food more frequently in the fall and
winter (Ghalambor et al. 1999, Sibley 2001). For other forest birds, the importance of epiphytes
in the non-breeding season remains unknown.
40
Section 3
Use of Resources and Availability
The relative frequency of epiphyte and host substrates use, and tree selection by foraging
birds revealed the relative importance of each substrate and tree species for that species, so I
could compare between species and foraging guilds. I compared epiphyte and host resources
availability and relative resource selection for five species (Chestnut-backed Chickadee, Redbreasted Nuthatch, Brown Creeper, Hairy Woodpecker and Gray Jay), and for all foraging bouts
captured in the Tree Plots and Walking Transects (data pooled). I also compared tree species
availability and tree species use during foraging bouts on epiphyte substrates, relative to foraging
bouts on host substrates. My null hypotheses were: species (and all foraging bouts) will use
resources in the same proportions (ratios) to their availability, as follows:
H01: Bird use of major resources is proportionate to resource availability:
Foliage: Branches and Stem Bark: Epiphytes is 0.12:1.00:0.01 (McCune 1997).
H02: Bird use of intra-epiphyte group is proportionate relative to intra-epiphyte group
availability: Alectorioid Lichens: Cyanolichens and Other Lichens: Bryophytes is:
0.28:0.72:1.00 (Harmon et al, 2004).
H03: Bird selection of tree species is proportionate relative to tree species availability:
Abies spp., P. menziesii: T. heterophylla: T. plicata: Others is:
0.25:0.29:1.00:0.05:0.15.
Epiphyte and Host Resource Use and Availability
In general, all five species used epiphytes disproportionately relative to the available
resource pool. Epiphytes were used disproportionately when the data were analyzed by species,
pooled across species, and pooled by survey procedure (Table 16; Appendix G). Epiphyte use
among the five species ranged from 30% (Chestnut-backed Chickadee) to 53% (Brown Creeper).
Epiphyte substrates were used less frequently than branch and stem bark (34% vs. 39%) and more
frequently than foliage, but in all cases disproportionately relative to epiphyte and phorophyte
availability. Foliage was used more frequently by Chestnut-backed Chickadee, whereas Hairy
Woodpecker avoided the resource. With the exception of Brown Creeper, the bark insectivores
41
(Red-breasted Nuthatch, and Hairy Woodpecker) used branches and bark stem more frequently
than foliage or epiphytes. When the log-likelihood ratio test was performed on pooled data of all
individual foraging bouts (N = 505), the disproportionate use of epiphyte substrates, relative to
non-epiphyte resources (foliage, branches, stem bark, and understory shrubs and herbs), was more
apparent (Gadj = 1,303, P < 0.005).
Table 16: Relative availability of host and epiphyte resources (g Cm-2) and their proportional use
(%) by five species; Tree Plot and Walking Transect data pooled.
Resource Pool
Available Resources1 (%)
Foliage
Branches and
Stem Bark
Epiphytes
941 (10.2)
8144 (88.7 )
100 (1.1 )
English Name2
Proportionate Use
Gadj
Critical
χ2
P
Chestnut-backed Chickadee
43.8
26.3
30.0
238.83
3.84
< 0.05
Red-breasted Nuthatch
19.6
48.2
32.1
54.91
5.99
< 0.01
Gray Jay
28.8
36.5
34.6
170.20
5.99
< 0.005
Brown Creeper
2.0
45.1
52.9
77.29
5.99
< 0.01
Hairy Woodpecker
0.0
69.8
30.2
23.66
5.99
< 0.025
All five species
27.1
38.6
34.3
930.13
5.99
< 0.005
1
2
Estimated stores of carbon associated with live biomass (Harmon et al. 2004), Total foraging
bouts (n): Chestnut-backed Chickadee (160), Red-breasted Nuthatch (56), Gray Jay (104), Brown
Creeper (51), Hairy Woodpecker (43), all species (414).
When pooled, the five species used epiphyte groups disproportionately, relative to the
available epiphyte resource pool. Cyanolichens and other lichens were used disproportionately
more often, whereas bryophytes were used disproportionately less often (P < 0.005, Table 17).
When the log-likelihood ratio test was performed on pooled data of all epiphyte foraging bouts by
all species (N = 172), the disproportional use of intra-epiphyte substrates was still significant (Gadj
= 12.3, P < 0.05). Chestnut-backed Chickadees foraged disproportionately on cyanolichens and
other lichens, relative to alectorioid lichens and bryophytes (P < 0.05, Table 17, Appendix H).
Red-breasted Nuthatch foraged disproportionately on cyanolichens and other lichens, however,
42
the variation between the expected values and the observed values were not statistically
significant (P > 0.05). Gray Jays foraged on live foliage and epiphytic substrates in significantly
greater proportions, relative to the availability of branches and stem bark (P < 0.005). Gray Jays
used bryophytes and cyanolichens and other lichens in the same proportions (38.9% of foraging
bouts), however, the expected values were not significantly different than the observed values (P
> 0.1). Brown Creepers used epiphytic substrates during more than half of their foraging bouts,
and foraged significantly more often on epiphytic resources than host resources (P < 0.01).
Brown Creeper also frequently used bole and branch bark devoid of epiphytes, and live foliage
was generally avoided. Hairy Woodpeckers did not use the major resources proportionately (P <
0.025), foraging primarily on stem and branch bark, whereas approximately one third of their
foraging bouts included epiphytic substrates.
Table 17: Relative availability of epiphyte groups (kg ha-1) and their proportionate use (%) by
five species, Tree Plot and Walking Transect data pooled.
Epiphyte Group
Available Resources1 (%)
Alectorioid
lichens
Cyanolichens
& Other
lichens
Bryophytes
934 (14.1)
2382 (35.9)
3316 (50.0)
English Name2
Proportionate Use
Gadj
Critical
χ2
P
Chestnut-backed Chickadee
16.7
60.4
22.9
15.53
5.99
< 0.05
Red-breasted Nuthatch
11.1
77.8
11.1
12.06
3.80
> 0.05
Gray Jay
22.2
38.9
38.9
2.44
5.99
> 0.1
Brown Creeper
14.8
37.0
48.2
0.04
5.99
> 0.1
Hairy Woodpecker
0.0
38.5
61.5
3.67
3.84
> 0.1
All five species
15.5
50.7
33.8
16.19
5.99
< 0.05
1
McCune 1993, McCune et al. 1997; 2 Sample sizes (n): Chestnut-backed Chickadee (48), Redbreasted Nuthatch (18), Gray Jay (36), Brown Creeper (27), Hairy Woodpecker (13), and All five
species (142).
43
Tree Use and Availability
When all foraging bouts were pooled, birds used tree species proportionately, relative to
their availability (N = 578, log-likelihood ratio test: Gadj = 6.75 < critical chi square value of 9.5;
P < 0.05). For all foraging substrates, T. heterophylla (the most common tree species in the
forest) was used more frequently than any of the other tree species (Table 18). Birds rarely used
T. plicata; this tree species was relatively rare in the forest. When all epiphyte-related foraging
bouts were pooled, all four dominant trees were used disproportionately (N = 171, P < 0.025).
Pseudotsuga menziesii, and “Other Species” were used disproportionately more frequently,
whereas T. heterophylla, Abies spp., and T. plicata were used less frequently, relative to their
availability. Approximately 73% of all epiphyte-related foraging bouts occurred on P. menziesii
and T. heterophylla, proportionate to their combined availability of 74%. Foraging bouts
involving bryophytes rarely occurred on P. menziesii, whereas P. menziesii was used more
frequently when lichen substrates were used. Snags and Others and Abies spp. were used
disproportionately more frequently during the bouts that involved bryophyte substrates. Birds
used P. menziesii and Abies spp. disproportionately more often when they used foliage, and when
phorophyte resources were pooled (N = 392, P > 0.05).
Three of the four dominant tree species provided epiphyte foraging substrates for all five
foraging guilds (AI, BI, LUHI, OS, and TFI). Thuja plicata was never used during epiphyte
foraging bouts except by OS (Table 19). In general, OS proportionate use of tree species during
foraging bouts on epiphyte substrates mirrored their proportionate bouts on phorophyte substrates
(P < 0.05 for both). Approximately half of all OS and TFI foraging bouts on epiphyte and
phorophyte substrates occurred on T. heterophylla. When foraging on phorophyte substrates, P.
menziesii and Abies spp. were used disproportionately more frequently by BI and TFI,
respectively (P < 0.05 for both). Conversely, during bouts on epiphytes, BI and TFI used “Other
Species” more frequently, relative to their availability, although the log likelihood ratio test
statistics were not statistically significant (P > 0.1). Brown Creepers and Red-breasted
Nuthatches used T. heterophylla more frequently when foraging on epiphyte substrates, relative
to T. heterophylla availability of 57% (Appendix I). In contrast, the Hairy Woodpecker did not
show a similar preference for T. heterophylla, and used “Other Species” and Abies spp.
disproportionately more frequently. In general, Chestnut-backed Chickadees used tree species
proportionately during bouts on epiphytes, although the Chickadees used P. menziesii during 25%
of their bouts, relative to P. menziesii availability of 17%.
44
Table 18: Relative availability of tree species (relative %) and their proportional use (%) by all species during foraging bouts on epiphyte and
host substrates, Tree Plot and Walking Transect data pooled.
Available Resource Pool Tree Species1
Available2
PSME
TSHE
ABSP
THPL
OTHERS
17
57
14
3
9
Foraging Substrate
Proportionate Use (%)
Gadj
Crit. χ2
P
9.9*
7.8
<0.05
Alectorioid Lichens
34.6
53.8
7.7
0
3.8
Cyanolichens & Other Lichens
24.7
56.5
9.4
1.2
8.2
Bryophytes
4.7
46.9
17.2
1.6
29.7
23.0
7.8
<0.005
All Epiphytes
19.3
53.2
10.5
1.2
15.8
13.1
9.5
<0.025
Foliage
21.8
57.6
18.2
0.6
1.8
22.3
9.5
<0.005
Bark or Branches
19.8
52.5
17.5
4.0
6.2
4.9
9.5
<0.05
All Phorophytes
18.4
55.9
15.6
2.0
8.2
2.9
9.5
>0.05
0
87.5
12.5
0
0
n/a
n/a
n/a
Other
37.5
50.0
12.5
0
0
n/a
n/a
n/a
All Substrates
18.7
55.4
14.0
1.7
10.2
6.75
9.5
<0.05
Mistletoe
1
ABSP = Abies spp., PSME = Pseudotsuga menziesii, TSHE = Tsuga heterophylla, THPL = Thuja plicata, Others = Cornus nuttallii, Taxus brevifolia, Snags.2
Data were provided by the Permanent Study Plot program, a partnership between the H.J. Andrews Long-Term Ecological Research program and the U.S. Forest
Service Pacific Northwest Research Station, Corvallis, OR; *All lichen foraging bouts pooled for log-likelihood ratio test (n = 108)
45
Table 19: Relative availability of tree species (%) and their proportional use (%) by seven foraging
guilds during foraging bouts on epiphyte and host substrates, Tree Plot and Walking Transect data
pooled.
Available Resource Pool Tree Species1
Available2
Foraging
Guild
PSME
TSHE
ABSP
THPL
OTHERS
17
57
14
3
9
Foraging
Substrate (n)
Proportionate Use (%)
Gadj
Critical
χ2
P
Epiphytes (5)
20.0
60.0
20.0
0
0
n/a
n/a
n/a
Host (29)
3.4
69.0
17.2
6.9
3.4
n/a
n/a
n/a
Epiphytes (57)
14.0
59.6
12.3
0
14.0
1.7
7.8
>0.1
Host (94)
25.5
44.7
11.7
1.1
17.0
9.7
7.8
<0.05
Epiphytes (15)
20.0
40.0
20.0
0
20.0
n/a
n/a
n/a
Host (24)
8.3
45.8
25.0
4.2
16.7
n/a
n/a
n/a
Epiphytes (38)
21.1
50.0
5.3
5.3
18.4
6.9
7.8
<0.05
Host (66)
22.7
51.5
7.6
4.5
13.6
6.0
7.8
<0.05
Epiphytes (2)
50.0
50.0
0
0
0
n/a
n/a
n/a
Host (9)
12.5
50.0
25.0
0
12.5
n/a
n/a
n/a
Epiphytes (50)
24.0
56.0
10.0
0
10.0
2.3
7.8
>0.1
Host (135)
17.8
54.1
23.7
0.7
3.7
15.5
7.8
<0.025
Epiphytes (4)
0
0
0
0
100.0
n/a
n/a
n/a
Host (40)
12.5
87.5
0
0
0
n/a
n/a
n/a
Epiphytes (171)
19.3
53.2
10.5
1.2
15.8
13.1
9.5
< 0.025
Host (392)
18.4
55.9
15.6
2.0
8.2
2.9
9.5
> 0.05
AI
BI
LUHI
OS
N
TFI
TS
All Guilds
1
ABSP = Abies spp., PSME = Pseudotsuga menziesii, TSHE = Tsuga heterophylla, THPL = Thuja plicata,
Others = Cornus nuttallii, Taxus brevifolia, Snags.2 Data were provided by the Permanent Study Plot program, a
partnership between the H.J. Andrews Long-Term Ecological Research program and the U.S. Forest Service
Pacific Northwest Research Station, Corvallis, OR; AI = aerial insectivore, BI = bark insectivore, LUHI= lowunderstory herbivore/insectivore, N = nectarivore, OS = omnivore scavenger, TFI = timber foliage insectivore,
TS = timber seed-eater.
46
Discussion
Chestnut-backed Chickadees, Red-breasted Nuthatches, Gray Jays, Brown Creepers, and
Hairy Woodpeckers showed selectivity in use of the major foraging resources. When the five
species were pooled, epiphyte-groups were used disproportionately, with cyanolichens and other
lichens used disproportionately more often and bryophytes less often, whereas alectorioid lichens
were used proportionately, relative to their availability. The disproportionate use of bryophytes
by Chestnut-backed Chickadees was consistent with Weikel and Hayes’ (1999) study that
documented this species selecting live trees with relatively low bryophyte cover. In their study of
young coniferous forests, Weikel and Hayes (1999) grouped all lichen and moss epiphyte forms
into their categorical variable “bryophytes”. The relatively low use of bryophytes by Chestnutbacked Chickadees in young and old forests may be a function of beak size. Chickadees are
small passerines (<10 g), with small, short beaks. Compared with the larger and longer bills of
Gray Jay and Hairy Woodpecker, Chickadee (and Red-breasted Nuthatch) beaks are less wellsuited to extract invertebrates concealed within appressed bryophytes. Gray Jays probed or
plucked food items while perched upon appressed bryophytes, whereas Hairy Woodpeckers
hammered and pecked through densely appressed bryophytes. Although Brown Creepers also
have small bills and are slightly smaller than Chickadees, Creepers used bryophytes by hanging
upside-down beneath large branches while searching bryophytes, a foraging posture that is
unavailable to Chickadees.
Trees were used disproportionately during bouts on epiphytes. P. menziesii and T.
heterophylla were used more frequently but in proportion to their availability, accounting for 77%
of all epiphyte foraging bouts on dominant and codominant trees. Foraging bouts on bryophyte
substrates rarely occurred on P. menziesii whereas “Other Species” and T. heterophylla were used
disproportionately more often. However, tree species and epiphyte habitats and distribution are
interdependent: P. menziesii and T. heterophylla constituted the tallest components of the
coniferous forest, and are associated with increased species richness and biomass of lichens
(McCune et al. 2000). Conversely, most bryophyte-related foraging bouts occurred in the lower
strata of the forest, on T. brevifolia, and understory shrubs, which are associated with higher
species richness and biomass of bryophytes.
The paucity of foraging activities on T. plicata could be explained by their relative rarity
in the forest: T. plicata accounted for only 3% of the relative tree species abundance.
Alternatively, avoidance of T. plicata might be due to phytophagous insects avoiding the
secondary compounds (tannins and oils) produced by T. plicata, which would in turn limit
47
insectivorous birds. Calocedrus decurrens is avoided by insectivorous birds during the breeding
season (Ariola and Barret 1985).
With the exception of foraging bouts on bryophytes, birds used dominant and codominant trees more frequently than intermediate or suppressed trees. This could be a function of
survey location where most observations were recorded in the canopy and where these tree
classes are more abundant. The vertical stratification and distribution of epiphyte groups is well
documented, with the greatest cover of epiphytes occurring in the mid crown of large trees
(McCune 1993, Lyons et al. 2000). Alternatively, the greater use of dominant, codominant and
suppressed trees may be relative: these tree classes were the most available resource (Table 3).
However, many cavity-nesting birds also show a preference for larger diameter trees as foraging
locations (Weikel & Hayes 1999).
48
Section 4
Community Structure
Results for Epiphyte Foraging Events
The MRPP statistics indicated less heterogeneity within, and greater heterogeneity among
epiphyte groups and substrates, than was expected by chance (A = 0.177 for epiphyte groups, and
A = 0.215 for finer scale epiphyte substrates, P < 0.001) (Table 20). Similarly, overall MRPP
runs of crown class, vertical canopy crown class, foraging posture, tree species and position of the
bird in the tree showed within-group similarities, and among-group dissimilarities. The threedimensional NMS solution explained 93% of the variability in the data (39.9% (Axis 1) + 33.0%
(Axis 2) + 20.1% (Axis 3) (Figs. 6 and 7). Final stress for the three-dimensional solution was
14.38 (final instability = 0.061). Results of the Monte Carlo procedure with 250 randomized
runs, and 250 runs of real data showed that the NMS real data runs produced a relatively stronger
structure than expected by chance (P = 0.004). The NMS ordination (Figs. 6 and 7) supported the
MRPP statistic, which indicated both less heterogeneity within foraging guild and species groups,
and greater heterogeneity among groups, than expected by chance.
Foraging guilds and species: The MRPP showed strong similarities and separation
among several of the foraging guilds (Table 20, Appendices K and L). MRPP indicated both less
heterogeneity within foraging guilds, and greater heterogeneity between foraging guilds, than
expected by chance (A = 0.178, P < 0.001). The overall chance-corrected within-species and
within-foraging guild agreement statistics were strongly heavily influenced by the LUHI. Winter
Wrens comprised the majority of the LUHI data, and showed clear separation from all other nonLUHI foraging guilds and associated species (Figs. 6 and 7, Appendices K and L). Conversely,
within LUHI group comparisons indicated broad overlapping of foraging strategies (e.g., A =
0.077, P < 0.001 for WIWR vs. DEJU; and A = 0.006, P = 0.282 for WIWR vs. HETH). The
high P-value reflects the low sample size of Hermit Thrush epiphyte foraging activities. As guild
members, the foraging behaviors and strategies of Winter Wren, Dark-eyed Junco, and Hermit
Thrush using epiphytic substrates differed significantly from those strategies employed by most
members of the other foraging guilds (Appendices M and N). Strong among-group patterns were
observed among LUHI and five foraging guilds, namely the AI, BI, OS, TFI, and TS.
Nectarivores was the only foraging guild that showed weak patterns with LUHI. Strong amonggroup patterns were also observed among TS and two foraging guilds, namely AI and N. The
49
OS, BI, and TFI guilds showed weak within-group patterns among their foraging behaviors,
suggesting these guilds used similar foraging strategies.
Table 20: Comparison of differences in epiphyte related foraging strategies with non-metric
Multi-Response Permutation Procedures, based on Sørensen distances; g = number of groups; A =
chance-corrected within-group agreement; P = probability of Type I error for Ho: no difference
between groups. Bonferroni-adjusted significant P-values indicating among group dissimilarity
and within group similarity are highlighted in bold.
Pooled Data (N = 191)
A value
P
Major epiphyte groups1
4
0.177
< 0.001
Finer scale epiphyte groups2
8
0.215
< 0.001
3
7
Foraging Guilds
0.178
< 0.001
13
Species4
0.231
< 0.001
5
4
Crown class
0.225
< 0.001
3
0.063
0.001
Horizontal Crown6
7
Vertical Crown
5
0.149
< 0.001
8
Foraging Maneuver
6
0.038
< 0.001
10
Foraging Posture9
0.105
< 0.001
6
Tree Species10
0.215
< 0.001
Tree Condition11
2
0.081
< 0.001
12
Tree Position
5
0.108
< 0.001
1
alectorioid lichen, cyanolichen and other lichen, bryophyte, lichen/bryophyte admixture; 2
alectorioid lichen, foliose lichen, fruticose lichen, fruticose and foliose lichen, pendant
bryophyte, appressed bryophyte, other lichen, bryophyte and lichen; 3 aerial insectivores, bark
insectivores, nectarivores, low-understory herbivore/insectivores, omnivore-scavengers, timber
foliage insectivores, timber seed-eaters; 4 Brown Creeper, Chestnut-backed Chickadee; Darkeyed Junco, Golden-crowned Kinglet, Gray Jay, Hairy Woodpecker, Hermit Thrush, Pacificslope Flycatcher, Red-breasted Nuthatch, Red Crossbill, Rufous Hummingbird, Steller’s Jay,
Winter Wren; 5 dominant, codominant, intermediate, suppressed; 6 inner, middle, outer live
crown; 7 above, upper, middle, lower, below live crown; 8 hammer, glean, probe, peck, pluck,
search;9 hang, hang upside-down, hop, hover, lean over/into, perch, reach under, short flight,
stand, walk/run; 10 Pseudotsuga menziesii, Tsuga heterophylla, Abies spp., “Pinus monticola,
Thuja plicata and Snags”, “Acer circinatum and Taxus brevifolia”, others; 11 live, dead; 12 bole,
branch, branchlet, dead branch/lets, foliage.
Groups
g
The NMS graphical representation also indicated that LUHI used different foraging
strategies when using epiphytes, relative to the other foraging guilds (Figs. 6 and 7). Although
widely spaced along Axis 2, LUHI showed a clear separation from all other guilds and species.
However, there was considerable overlap with several points, including OS, BI, and AI. For
example, the OS point that scored lowest on both Axes 2 and 3 was an individual Gray Jay that
was observed hammering a food item located in a pendant bryophyte on the branch of A.
50
circinatum at 2.25 m. Similarly, the low-scoring AI point was a Pacific-slope Flycatcher that
hover-gleaned at pendant bryophyte and fruticose lichen admixture at 6 m. This AI event
reflected the sole bryophyte-associated foraging bout on Abies spp., and the lowest epiphyte
foraging event by Pacific-slope Flycatcher, hence the separation on the ordination. The four Red
Crossbill points (Fig. 7) showed a tight clustering pattern, reflecting their specialized foraging
behavior. Conversely, Gray Jay points were widely distributed along both axes reflecting the
generalist nature of the scavengers’ foraging behaviors on epiphytes coupled with their ubiquitous
distribution throughout the vertical forest profile. In general, the points representing both the TFI
and BI foraging guild scored higher on both axes, reflecting similar foraging strategies. This was
also evident in the statistics from the multiple MRPP comparisons between the two guilds (and
species that represent the bulk of these data) that indicated extremely broad overlapping (A =
0.026 for guild comparison; and A = 0.018 for species comparison of Red-breasted Nuthatch and
Chestnut-backed Chickadee) (Appendices K and L).
Finer-scale epiphyte substrates: Finer-scale epiphyte substrates showed stronger and
more statistically significant patterns than obtained from the MRPP run with the coarser scale,
epiphyte functional groups (A = 0.215, P < 0.001) (Table 20). Foraging activities on epiphyte
substrates indicated similar within-group foraging behaviors, and among-group dissimilarities
between bryophyte groups and both lichen groups (Appendix J). Foraging activities on appressed
and pendant bryophyte groups differed considerably when compared with the lichen groups. The
strongest among-group patterns observed were among appressed bryophytes and three lichen
finer-scale substrates, namely alectorioid lichen, foliose and the foliose and fruticose admixture
(Appendix J). In addition, foraging behaviors for alectorioid lichens showed some separation
from the other lichen substrates. The strongest patterns were found between alectorioid lichens
and pendant bryophytes (A = 0.168, P < 0.001). The majority of the pairwise comparisons of
among-lichen and bryophyte finer scale substrates indicated dissimilar foraging strategies
(Appendix J). Conversely, most pairwise comparisons of within-lichen and within-bryophyte
finer scale substrates groups yielded statistics that indicated similar foraging strategies (Appendix
J). Pairwise comparisons of the remaining finer scale epiphyte substrate groups showed broad
overlap suggesting similar foraging strategies, or otherwise smaller sample sizes (Appendix J).
Epiphyte functional groups: There was both more homogeneity within epiphyte groups,
and greater heterogeneity between epiphyte groups, than expected by chance (A = 0.177, P <
0.001, Table 20). The comparisons of bryophyte and both lichen functional groups generated
51
statistics comparable to the overall comparison, with the strongest differences in foraging
strategies observed among bryophytes and lichens (Appendix J). The strongest among-group
pattern was observed among bryophytes and cyanolichens and others lichens (A = 0.169, P <
0.001), and then between “bryophytes” and “alectorioid lichens” (A = 0.155, P < 0.001).
Tree species: Use of tree species groups showed a strong pattern (A = 0.215, P < 0.001;
Table 20). The strongest patterns were among P. menziesii and two groups, namely A. circinatum
and T. brevifolia (A = 0.333, P < 0.001), and “ground, logs or other species” (A = 0.333, P <
0.001). Tsuga heterophylla showed similar but weaker patterns with these latter two groups
(Appendix J). These patterns implied that the foraging strategies used on epiphytes located on P.
menziesii and T. heterophylla were different than those strategies and behaviors used for the other
tree groups.
Crown class: The comparisons of crown classes indicated significantly different foraging
strategies (A = 0.225, P < 0.001), with the strongest patterns observed between suppressed trees
and all other crown classes (Table 20, Appendix J). Broad overlapping was observed within and
between dominant and codominant classes, and codominant and intermediate crown classes (A =
0.01, P < 0.05 for both). Bird use of epiphyte substrates was significantly different when
suppressed trees were used, relative to dominant, codominant and intermediate trees.
Vertical and horizontal crown use: No strong patterns were observed when comparing
overall use of the three horizontal tree zones (inner, middle, and outer zones, A = 0.063, P <
0.001). Conversely, use of the vertical crown zones showed significantly different foraging
strategies in these zones. Comparisons of above- and upper live crown versus lower and below
live crown categories generated statistics similar to the overall comparison (A = 0.103, P = 0.024;
A = 0.145, P = 0.052, respectively) (Appendix J).
Foraging maneuvers and postures: Overall comparisons of all foraging behaviors
indicated commonality in foraging maneuvers, but dissimilarities in foraging postures when using
epiphyte groups (A = 0.038 for maneuvers, A = 0.105 for postures, P < 0.105 for both).
Comparisons of foraging postures showed broad overlapping and all results were statistically
insignificant, save one: the comparison between “reach under” and “hopping” (A = 0.113, P =
0.037) (Table 20, Appendix J). Foraging strategies used by LUHI on all substrates and by all
guilds on bryophytes accounted for most of the differences in foraging strategies between the
52
guilds and epiphyte groups. Five foraging postures (hopping, hovering, standing,
walking/running and reaching-up) showed among group dissimilarity and within group similarity.
These five postures were used more frequently by the LUHI and AI guilds, respectively, which
contributed to among-foraging guild differences.
Tree position and condition: Overall comparison of tree positions was statistically
significant, and stronger agreement than from the comparisons of tree condition (A = 0.108, P <
0.001). Statistically significant strong patterns were obtained from comparisons of two tree
position pairs: branchlet versus bole groups (A = 0.178, P < 0.001), foliage versus bole groups (A
= 0.142, P < 0.001). No strong patterns were observed when comparing overall use of live versus
dead trees.
Foraging Height: Both the correlation coefficients and scatterplots indicated an
environmental gradient, with the vertical stratification of foraging guilds, where foraging height
maintained a positive relationship with guild foraging strategies and behaviors. Axis 2 showed a
strong positive correlation with height, where specific foraging guilds showed distinct linear and
rank relationships. When the ordination was rotated -135 degrees, the linear correlation
coefficients between foraging height and the ordination represented by Axes 1, 2 and 3 were
0.528, 0.956, and -0.107, respectively, which explained 27.9, 91.4 and 1.1 percent of the
variation (R2), respectively. R-squared denoted the proportion of variation expressed by the
ordinated position on each respective axis that was explained by the variable (McCune and Grace
2002). The rank correlation coefficients represented by Axes 1, 2 and 3 were 0.472, 0.820, and 0.051, respectively.
53
Axis 2
Axis 3
Axis 1
Axis 2
Axis 3
Guild
AI
BI
LUHI
N
OS
TFI
TS
Figure 6: Nonmetric multidimensional scaling (NMS) ordination for 191 individuals with
different symbols for seven foraging guilds whose members foraged on epiphyte substrates
(Foraging Guilds: AI – aerial insectivores, BI – bark insectivores, LUHI – low understory
herbivores/insectivores, N = nectarivore, OS – omnivore/scavenger, TFI – timber-foliage
insectivores, TS – timber-seed eaters.
Axis 1
54
Axis 2
Axis 3
Species
BRCR
CBCH
DEJU
GCKI
GRAJ
HAWO
HETH
NOFL
PSFL
RBNU
RECR
RUHU
STJA
WIWR
Axis 3
Axis 2
Axis 1
Figure 7: Nonmetric multidimensional scaling (NMS) ordination for 191 individuals with different
symbols for fourteen species observed using epiphyte substrates in the Tree Plots (Species: BRCR =
Brown Creeper, CBCH = Chestnut-backed Chickadee, DEJU = Dark-eyed Junco, GCKI = Goldencrowned Kinglet, GRAJ = Gray Jay, HAWO = Hairy Woodpecker, HETH = Hermit Thrush, NOFL =
Northern Flicker, PSFL = Pacific-slope Flycatcher, RBNU = Red-breasted Nuthatch, RECR = Red
Crossbill, RUHU = Rufous Hummingbird, STJA = Steller’s Jay, WIWR = Winter Wren.
Axis 1
55
Discussion
The NMS and MRPP differentiated the overall species and foraging guild groups based on
foraging locations and foraging strategies by which birds used epiphytes. The species contributing
to the separation of foraging guilds were Winter Wren, Dark-eyed Junco, Rufous Hummingbird,
and Red-Crossbill, and the most important epiphyte substrates that contributed to the separation of
foraging guilds and species were appressed and pendant bryophytes and the admixture of fruticose
and foliose lichens. To a lesser degree, tree species, crown class and vertical crown location were
also important factors.
Evaluating and interpreting the quality of any ordination requires both statistical
considerations as well as a posteriori knowledge (McCune and Grace 2002). The cluster of bird
activity between 20 and 30 m is not unlike the vertical profile of surface area density and
distribution of foliage characteristic of forest stands (Nadkarni et al. 2004, see Fig. 1-2; Ishii et al.
2004, see Fig. 5-3). This cluster of bird activity coincides with the unimodal vertical distribution of
foliage in mature and old-growth forests (at least for closed canopy forests), with the greatest
values occurring in the 20 to 30 m profile of T. heterophylla and P. menziesii old-growth forests
(Ishii et al 2004). Broad overlapping of foraging strategies and behaviors among alectorioid lichen
and cyanolichen and other lichen groups may be explained by the tendency for alectorioid lichens
to occur both in the upper outer canopy as well as on the bole in the interior and lower canopy,
sympatric with cyanolichens and other lichens.
Among the five foraging guilds, LUHI and TS showed the strongest pattern of dissimilarity
among all other guilds. Strong patterns implied a gradient in the foraging strategies among these
foraging guilds, representing similar foraging strategies within groups, and dissimilarities among
groups. These strong patterns and the ordination suggested a vertical gradient (or structure) in
foraging guild use of epiphyte substrates which encompassed the height variable. The stratification
of foraging guilds in the vertical profile of the old-growth forest stand is consistent with the vertical
stratification of bird assemblages found by others (Lundquist and Manuwal 1990, Shaw et al.
2002). Although the majority of the sample units were clustered in the mid canopy, the graphical
ordination reflected a gradient in foraging guild structure, as follows (listed in decreasing foraging
height): TS: BI: OS: TFI: AI: LUHI. The relatively tight cluster of larger symbols from four
foraging guilds (OS, TFI, BI, and TS) reflects a pattern of similarity among the individuals which
concentrated activity in the mid to upper canopy. Timber-foliage insectivores and BI often foraged
together in mixed-flocks and used epiphytes in the same vicinity of the canopy where they used
56
phorophyte resources. This gradient also reflects the rank order of mean foraging heights for each
foraging guild (Table 14).
The variables foraging height, crown class, and tree species are confounded. Phorophyte
and epiphyte abundance are interdependent: larger trees with large branches support more
epiphytes throughout the vertical profile of the forest (Clement and Shaw 1999). Tree species and
epiphyte habitats and distribution are interdependent: P. menziesii and T.heterophylla constituted
the tallest components of the coniferous forest, and are associated with increased species richness
and biomass of lichens (McCune et al. 2000). Epiphytes are stratified vertically: understory
shrubs, suppressed and small trees (e.g., A. circinatum and T. brevifolia) support more abundant
bryophyte communities, relative to lichens which are more abundant with increasing height (i.e.,
larger trees). Thus, the dissimilarities among lichens and bryophytes may be explained by the
prevalence of bryophytes in the lower forest strata which necessitate different foraging strategies
than those used on lichens.
Although TFI, OS and BI concentrated their activities in portions of the canopy that
support the most foliage and cover of epiphyte groups, their wide-ranging distribution on the
ordination illustrates their opportunistic foraging nature and propensity to forage throughout the
vertical and horizontal profile of the forest, while using a wide variety of postures and maneuvers.
TS used the mid and upper canopy more often, and their close proximity in the graphic can be
explained by similar foraging strategies used when probing or searching lichens when they perched
at 40 m and 50 m. The low foraging profile and use of substrates unique to the ground level by
LUHI explain their scattered distribution along Axis 3 and lower scores on Axis 2, contrasting with
OS, BI and TFI, which used epiphytes throughout the vertical forest profile.
Possible explanations for the among-group heterogeneity in tree position might be that
only one species (Brown Creeper) used appressed bryophytes and bark lichens on the bole of the
tree, whereas branchlet and dead branch tree positions were each used by species from four
different foraging guilds. Fruticose, foliose and alectorioid lichens located on branchlets were used
by four species (Chestnut-backed Chickadee, Red-breasted Nuthatch, Steller’s Jay, and Red
Crossbill). Epiphytes located on dead branches were used by all four aforementioned species and
two others (Gray Jay and Hairy Woodpecker).
MRPP indicated that use of epiphyte substrates differed among suppressed trees and the
other tree classes (e.g., dominant, codominant and intermediate trees). The vertical stratification of
epiphytes is a likely explanation for the strong patterns observed among tree classes and vertical
canopy zones. The relative cover of lichen epiphyte groups generally increase with increasing
height above 20 m (Lyons et al. 2000). This height clustering is also associated with the critical
height limit for bryophytes, 28 m (McCune et al. 1997). Bryophytes are located in the lower forest
57
profile, and birds are using the resources accordingly. The NMS ordination showed a clustering of
foraging guilds (e.g., OS, TFI, and BI). These guilds also used similar foraging strategies on
phorophyte resources, which suggests that birds may optimize foraging opportunities if they
concentrate their foraging activities in portions of the canopy that yield the majority of the
available resources. In addition, sympatry in the mid to upper canopy by OS, TFI, and BI is
consistent with the notion that PNW birds are generalists (Sharpe 1996).
It appears that observer location is a good predictor of epiphyte group and tree species use.
Most canopy-level observations captured foraging activity at greater heights, and since epiphytes
are vertically stratified in the forest, the canopy-level observations captured birds using bryophytes
less frequently than lichens, relative to those observations gathered in the ground-based Walking
Transects. Thus, resource availability and proportionate resource use by birds is influenced by the
field method used to capture such foraging and habitat preferences. Hence, a more accurate
assessment of resource use should include a combination of canopy-level and ground-based field
methods.
58
Section 5
Comparison of Methods
This section is divided into two subsections. Subsection 1 is a comparison between
foraging data captured in the two sampling procedures (Tree Plots and Walking Transects). A
comparison is necessary since most ornithological field work is conducted at the ground level, and
rarely has behavioral activity been recorded from the canopy level in temperate forests. Subsection
2 is the results of the comparative point count assessment between ground and canopy-level
observers in the Tree Plots.
Subsection 1
Comparison between Tree Plot and Walking Transect Sampling Procedures
Duration of all bird observations (including all foraging and non-foraging observations)
from all Walking Transects and Tree Plot sequences tallied 14.2 hrs, from 862 individuals of 32
species (Table 21). Compared with the Tree Plots, the Walking Transects yielded a greater number
of behavioral observations per hour (2.8 vs. 2.1) and sequences per hour (11.9 vs. 6.9), relative to
the total survey time of each sampling procedure. Similarly, the cumulative number of foraging
bouts (735) was not equally distributed amongst species or sampling procedure (Table 22).
The 237 foraging bouts captured in the Tree Plots represented 18 species from eight
foraging guilds, whereas the 498 bouts recorded during the Walking Transects included 25 species
from nine foraging guilds. Foraging data obtained from the Walking Transects yielded more than
twice the number of species and individuals per day, relative to the Tree Plots (t = 2.55, P = 0.016,
df = 30, Table 23). The Walking Transects captured more observations per hour (2.3 vs. 1.9) and a
greater number of behavioral sequences per hour (10.1 vs. 6.0) when calculated as a function of
total survey time. Members of the low understory herbivore/insectivore foraging guild (LUHI),
namely Hermit Thrush, Dark-eyed Junco, and Winter Wren, were poorly represented in the Tree
Plots, relative to the Walking Transects (Fig. 8, Table 24). The vast majority of behavioral
activities collected in the Tree Plots were captured from the canopy level (80%), and no sequence
data in the Tree Plots were recorded at ground level for 3 of the 20 days.
The Chestnut-backed Chickadee was the most frequently detected species during both
survey procedures (Fig. 8). Gray Jay, Red Crossbill and Red-breasted Nuthatch were the next most
59
frequently detected species in the Tree Plots, and these four species accounted for approximately
75% of all Tree Plot foraging data. The numbers of Red Crossbill individuals observed per day in
the Tree Plots were significantly higher than those observed during the Walking Transects. At the
canopy level, Red Crossbills were easily observed, and individuals within large flocks could be
differentiated due to sexual dimorphism in plumage. Foraging data for Winter Wren were obtained
each day of the Walking Transects and were the second most frequently detected species.
Chestnut-backed Chickadee and another five species (Winter Wren, Gray Jay, Pacific-slope
Flycatcher, Hairy Woodpecker, and Brown Creeper) accounted for approximately 75% of the
Walking Transect data (Table 25).
The Tree Plots recorded foraging data for four species that were never encountered during
the Walking Transects (Fig. 8, Table 24). Two of the four species, Hermit Warbler and Pine
Siskin, typically use upper canopy foliage and seed resources, and the remaining two species
(Vaux’s Swift and the Turkey Vulture) forage while flying above the canopy. The Walking
Transects captured foraging data for 11 species that were never detected in the Tree Plots (Fig. 8).
Table 21: Behavioral activity (foraging and non-foraging activity) data summary by survey
procedure.
Survey Procedure
Walking Transects
Tree Plots
Canopy Location Only
Ground Location Only
Tree Plots subtotal
Total
11.13
Number of
Individuals
601
2.15
0.91
3.06
14.19
211
50
261
862
Time (hrs)
# Species
# Sequences
30
2,549
17
10
19
32
710
137
847
3,396
Table 22: Searching and foraging bout survey effort summary by survey procedure.
Survey Procedure
Walking Transects
Tree Plots
Canopy Location Only
Ground Location Only
Tree Plots subtotal
Total
5.94
Number of
Individuals
498
1.78
0.38
2.16
8.10
195
42
237
735
Time (hrs)
# Species
# Sequences
25
2,162
16
8
18
29
642
98
740
2,902
60
Table 23: Number of foraging species, individuals and foraging guilds (mean SE) detected per
day and by survey procedure.
Survey Procedure
Tree Plots
Walking Transects
Species per day
3.90 ± 0.41
9.55 ± 0.41
Individuals per day
11.85 ± 2.18
24.90 ± 1.79
Foraging guilds per day
3.25 ± 0.29
5.70 ± 0.21
1
Student’s t-test comparison between survey procedures, df = 19, = 0.05
Comparison1
Category
t = 9.49, P< 0.001
t = 4.087, P < 0.001
t = 7.123, P < 0.001
Walking Transects
Tree Plots
BTPI (1)
BRCR (51)
CONI (1)
CBCH (167)
BDOW (2)
GCKI (21)
BHGR (1)
DEJU (22)
HEWA (2)
PISI (2)
GRAJ (108)
HAFL (3)
HAWO (43)
HETH (18)
RECR (43) RBNU (60)
TUVU (1)
VASW (5)
NOFL (1)
NOPO (2)
PSFL (46)
PIWO (2)
RUHU (21)
RBSA (1)
VATH (2)
STJA (7)
WIWR (99)
WETA (3)
WIWA (1)
Figure 8: Venn diagram of species and foraging bouts (n) captured by survey procedure. Species
codes: BDOW = Barred Owl, BHGR = Black-headed Grosbeak, BRCR = Brown Creeper, BTPI =
Band-tailed Pigeon, CBCH = Chestnut-backed Chickadee, CONI = Common Nighthawk, DEJU =
Dark-eyed Junco, GCKI = Golden-crowned Kinglet, GRAJ = Gray Jay, HAFL = Hammond’s
Flycatcher, HAWO = Hairy Woodpecker, HETH = Hermit Thrush, HEWA = Hermit Warbler,
NOFL = Northern Flicker, NOPO = Northern Pygmy-Owl, PISI = Pine Siskin, PIWO = Pileated
Woodpecker, PSFL = Pacific-slope Flycatcher, RBNU = Red-breasted Nuthatch, RBSA = Redbreasted Sapsucker, RECR = Red Crossbill, RUHU = Rufous Hummingbird, STJA = Steller’s Jay,
TUVU = Turkey Vulture, VATH = Varied Thrush, VASW = Vaux’s Swift, WETA = Western
Tanager, WIWA = Wilson’s Warbler, WIWR = Winter Wren
61
Table 24: Total observation time (s), number of individuals (n) and sequences by survey type for
each bird species.
English Name
Foraging
Guild1
Tree Plots
Time
n
seq.
Walking Transects
Time
n
seq.
Band-tailed Pigeon
TS
-
2
1
1
Barred Owl
H
-
250
2
2
TFIO
-
3
1
1
Black-headed Grosbeak
Brown Creeper
BI
137
10
21
1279
41
165
Chestnut-backed Chickadee
TFI
1396
63
183
3016
104
391
Common Nighthawk
AI
2
1
1
Dark-eyed Junco
LUHI
-
1310
22
137
Golden-crowned Kinglet
TFI
71
3
10
458
18
76
Gray Jay
OS
1756
48
173
3018
60
254
Hairy Woodpecker
BI
148
5
19
3230
38
235
Hammond's Flycatcher
AI
4
1
2
13
2
2
Hermit Thrush
LUHI
5
1
1
793
17
82
Hermit Warbler
TFI
50
2
10
Northern Flicker
Northern Pygmy-Owl
BI
H
Pacific-slope Flycatcher
AI
Pileated Woodpecker
BI
Pine Siskin
TS
16
2
2
Red Crossbill
TS
1194
35
Red-breasted Nuthatch
BI
1696
33
Red-breasted Sapsucker
BI
Rufous Hummingbird
N
90
7
Steller’s Jay
OS
402
Turkey Vulture
H
40
Varied Thrush
LUHI
Vaux’s Swift
AI
Western Tanager
TFI
Wilson’s Warbler
LUHI
Winter Wren
LUHI
588
14
TOTAL
7778
237
101
-
45
1
1
-
117
1
5
1080
43
108
69
2
9
54
279
8
10
164
1129
27
153
42
1
8
10
290
14
27
4
33
199
3
16
1
1
3
6
-
-
82
-
-
24
2
4
3
1
1
-
167
3
16
-
1
1
1
44
4558
85
457
740
21375
498
2162
4
6
1
Foraging guild codes: AI = aerial insectivore, BI = bark insectivore, LUHI= low-understory herbivore/insectivore, N
= nectarivore, OS = omnivore scavenger, TS = timber seed-eater, TFI = timber foliage insectivore, TFIO = timber
foliage insectivore/omnivore, H = aerial predator (catch non-insectivorous prey).
62
Table 25: Number of foraging individuals (mean SE) detected per survey day, frequency of
detection, by survey procedure (frequency is the proportion of survey days that the species was
detected).
English Name
Band-tailed Pigeon
Tree Plots
Individuals/day
(min/max)
---
Freq.
---
Walking Transects
Individuals/day
Freq.
(min/max)
0.05 ± 0.05 (0/1)
0.05
Barred Owl
---
---
0.1 ± 0.07 (0/1)
0.1
Black-headed Grosbeak
---
---
0.05 ± 0.05 (0/1)
0.05
0.5 ± 0.22 (0/4)
0.3
2.05 ± 0.37 (0/6)
0.85
Chestnut-backed Chickadee
3.15 ± 0.94 (15/0)
0.65
5.2 ± 0.76 (1/14)
1
Common Nighthawk
0.05 ± 0.05 (0/1)
0.05
---
---
---
---
1.1 ± 0.24 (0/4)
0.7
Golden-crowned Kinglet
0.15 ± 0.08 (0/1)
0.15
0.9 ± 0.27 (0/4)
0.55
Gray Jay
2.4 ± 0.61 (0/7)
0.55
3 ± 0.42 (0/7)
0.9
Hairy Woodpecker
0.25 ± 0.01 (0/1)
0.25
1.9 ± 0.35 (0/6)
0.9
Hammond's Flycatcher
0.05 ± 0.05 (0/1)
0.05
0.1 ± 0.07 (0/1)
0.1
Hermit Thrush
0.05 ± 0.05 (0/1)
0.05
0.85 ± 0.27 (0/3)
0.4
Hermit Warbler
0.1 ± 0.10 (0/2)
0.05
---
---
Northern Flicker
---
---
0.05 ± 0.05 (0/1)
0.05
Northern Pygmy-Owl
---
---
0.05 ± 0.05 (0/1)
0.05
0.15 ± 0.11 (0/2)
0.1
2.15 ± 0.22 (0/4)
0.95
---
---
0.1 ± 0.07 (0/1)
0.1
0.1 ± 0.07 (0/1)
0.1
---
---
Red Crossbill
1.75 ± 1.31 (0/26)
0.15
0.4 ± 0.27 (0/5)
0.15
Red-breasted Nuthatch
1.65 ± 0.67 (0/11)
0.45
1.35 ± 0.30 (0/4)
0.65
Red-breasted Sapsucker
---
---
0.05 ± 0.05 (0/1)
0.05
Rufous Hummingbird
0.35 ± 0.15 (0/2)
0.25
0.7 ± 0.19 (0/3)
0.5
Steller’s Jay
0.2 ± 0.12 (0/2)
0.15
0.15 ± 0.08 (0/1)
0.15
Turkey Vulture
0.05 ± 0.05 (0/1)
0.05
---
---
Varied Thrush
---
---
0.1 ± 0.07 (0/1)
0.1
Vaux’s Swift
0.2 ± 0.12 (0/2)
0.15
0.05 ± 0.05 (0/1)
0.05
---
---
0.15 ± 0.11 (0/2)
0.1
Brown Creeper
Dark-eyed Junco
Pacific-slope Flycatcher
Pileated Woodpecker
Pine Siskin
Western Tanager
Wilson’s Warbler
Winter Wren
TOTAL
---
---
0.05 ± 0.05 (0/1)
0.05
0.7 ± 0.25 (0/4)
0.4
4.25 ± 0.48 (2/11)
1.0
11.85 ± 2.18 (1/39)
24.9 ± 1.79 (13/44)
63
Comparison between Sampling Procedures for Epiphyte Use
For both sampling procedures, approximately 28% of the foraging bouts involved epiphyte
substrates, and more than 60% of these records reflected individuals foraging on resources
provided by the host (Appendix M). Likewise, the relative proportion of species recorded using
epiphyte substrates was similar for both survey procedures (9 of 18 species, or 50% in the Tree
Plots, and 13 of 25 species, or 56% in the Walking Transects). However, the use of epiphyte
groups was not equally distributed among sampling procedures. For instance, 73% of Tree Plot
epiphyte foraging bouts involved cyanolichen and other lichens substrates; foliose lichens were the
most frequently exploited epiphyte substrate. In comparison, 60% of all epiphyte foraging bouts
captured in the Walking Transects involved bryophyte substrates. Although 11 species (from
seven foraging guilds) were recorded using bryophytes in the Walking Transect, four species
accounted for 63% of these data (in decreasing order of abundance: Winter Wren, Brown Creeper,
Chestnut-backed Chickadee, and Gray Jay). In contrast, the Tree Plots captured only eight
foraging bouts on bryophyte substrates by three species, Winter Wren, Gray Jay and Brown
Creeper. Foraging bouts on alectorioid lichens comprised less than 5% and 3% of all Tree Plot and
Walking Transect observations, respectively. Although more species were recorded using
cyanolichen and other lichen substrates in the Walking Transects, the proportion of individual
records on these substrates in the Tree Plots was generally higher than those recorded for the
Walking Transects (Appendix M).
In the Tree Plots, five of the six species assigned a degree of epiphyte specialization were
considered regular users of epiphyte substrates (e.g., Brown Creeper, Chestnut-backed Chickadees,
Gray Jay, Red-breasted Nuthatch and Winter Wren) (Appendix N). The sixth species, Red
Crossbill, used epiphytes occasionally. In the Walking Transects, 12 species were assigned a
degree of epiphyte specialization (Appendix O). Brown Creeper, Hairy Woodpecker, Gray Jay,
Winter Wren and Hermit Thrush used epiphytes regularly whereas the seven other species (e.g.,
Red-breasted Nuthatch, Chestnut-backed Chickadee, Golden-crowned Kinglet, Dark-eyed Junco,
Pacific-slope Flycatcher, Red Crossbill and Rufous Hummingbird) were occasional users.
64
Comparison between Sampling Procedures for Spatial and Substrate Specialization
The mean height of all foraging birds detected during the Walking Transects was
significantly lower than in the Tree Plots (Student T-test, t = -15.6, P < 0.001) (Table 26). When
LUHI observations were excluded, the Tree Plots captured birds foraging considerably higher than
the Walking Transects (34.2 m 0.9 for Tree Plots, as compared with 17.5 m 0.8 for the Walking
Transects; t = -13.31, P < 0.001). For both Tree Plots and Walking Transects, birds used
bryophytes lower in the canopy than lichen substrates (Table 26). Foraging activities on lichen
substrates were captured generally between 21 and 35 m in the Tree Plots, and between 14 and 31
m in the Walking Transects. The mean height of all Tree Plot foraging bouts on epiphytes was
almost three times higher than the Walking Transects (30 m vs. 12 m), whereas foraging bout
locations on phorophyte substrates was only twice as high (32 m vs.15 m).
In the Walking Transects, members of the BI foraging guild foraged significantly higher in
the canopy when using phorophyte resources, relative to epiphyte substrates (Table 27).
Observations in the Tree Plots showed no differences between epiphyte or host substrate foraging
heights but the Tree Plots did capture BI foraging activities generally higher in the canopy than
records obtained from the Walking Transects. For both survey methods, BI used bryophytes lower
in the canopy than lichen substrates. Red-breasted Nuthatches, which accounted for 69% of the
Tree Plot BI data, were captured foraging in the mid canopy and were never observed using
bryophytes. Conversely, Red-breasted Nuthatches comprised 38% of the Walking Transect BI
foraging data and were observed foraging on bryophytes.
For TFI, no within-survey method differences were found between the foraging heights on
epiphyte and phorophyte substrates (Table 28). However, the Tree Plot surveys appear to facilitate
a more reliable assessment of TFI foraging activity in the upper canopy. Among-survey mean
height comparisons showed that all recorded heights of all substrates used by TFI were higher in
the Tree Plots than the Walking Transects. For example, Chestnut-backed Chickadees, which
accounted for 93% and 83% of Tree Plot and Walking Transect TFI foraging activities,
respectively, were captured foraging significantly lower in the Walking Transects (16 m) as
compared to the Tree Plots (29 m) (t = 7.65, df = 152, P < 0.001). Similarly, the Tree Plots
captured Chestnut-backed Chickadees using epiphytic substrates at a mean height of 32 m,
compared with 15 m in the Walking Transects. This difference between survey procedures held
true on a finer scale when epiphyte groups were considered. For instance, in the Tree Plots,
Chestnut-backed Chickadees foraged higher on alectorioid lichen and “other lichen” substrates at
32 m and 32 m, respectively, as compared with 21 m and 24 m, respectively, in the Walking
65
Transects. In the Tree Plots, Chestnut-backed Chickadees foraged on epiphytic substrates at a
similar height, relative to host resource, whereas there was greater variation in foraging heights
when documented from the ground level during the Walking Transects.
Table 26: Mean foraging height (m SE) of all bird records by substrate and survey procedure.
Other
Phorophyte
Epiphyte
Substrate
Alectorioid lichen
Cyanolichen and other lichen
Foliose lichen
Fruticose lichen
Other lichen
Admixture (fruticose & foliose)
All cyanolichen and other lichen
Bryophyte
Pendant bryophyte
Appressed bryophyte
All bryophytes
Admixture (lichen & bryophyte)
All Epiphyte Substrates
Foliage (live and dead foliage)
Bark
Dead wood (includes rootwads)
Cone
Other (flower)
Mistletoe brooms
All Phorophyte Substrates
Air
Perched litter
Ground
Terrestrial herbs/mosses
Other
All Other Substrates
All Substrates Total
Tree Plots
Walking Transects
Height
Height
33.2 1.6
28.6 4.8
34.6 2.1
21.5 3.5
24.0 11.0
31.9 3.0
32.7 1.7
15.7 2.9
21.0 12.7
14.4 4.4
30.6 4.9
17.7 2.3
4.9 4.1
10.6 5.7
9.0 4.1
---
32.3 2.2
32.1 1.2
61.4 11.6
28.5 4.5
0
-----
7.5 7.7
3.4 0.9
5.8 0.8
10.0 1.9
11.6 1.1
16.3 1.4
13.7 1.2
14.9 2.5
35.7 2.7
2.4 1.4
33.2 8.2
15.4 0.9
17.6 3.9
2.0
0.05 0.05
0.02 0.01
1.0
48.7 10.5
6.4 1.8
32.2 1.1
13.5 0.7
30.2 1.6
34.1 1.7
28.3 2.1
22.4 4.6
42.7 2.4
0.5
66
Table 27: Mean bark insectivore foraging heights (m SE), and sample size (n) by substrate and
survey procedure (* includes non phorophyte and non-epiphyte substrates).
Tree Plots
Substrate
Height
n
Height
n
31.0
1
28.7 ± 0.8
6
34.0 ± 0.2
15
19.0 ± 0.3
14
32.0
1
7.9 ± 0.1
22
All Epiphyte Substrates
33.7 ± 0.2
17
14.6 ± 0.1
42
Foliage (live and dead foliage)
36.4 ± 0.5
5
34.1 ± 0.6
7
Bark
33.7 ± 0.1
20
17.3 ± 0.1
46
Wood
42.3 ± 1.3
3
29.4 ± 0.3
14
All Phorophyte Substrates
35.1 ± 0.1
28
21.6 ± 0.1
67
34.2 ± 0.1
48
19.1 ± 0
110
Phorophyte
Epiphyte
Alectorioid lichen
Cyanolichen and other lichen
Bryophyte
All Substrates*
Comparison
1
Walking Transects
1
t = -0.44, df = 43, P = 0.33
t = -2.35, df = 107, P = 0.02
Student’s t-test, cumulative epiphyte and phorophyte comparison by survey type, = 0.05
Table 28: Mean timber-foliage insectivore foraging heights (m SE), and sample size (n) by
substrate and survey procedure (* includes non phorophyte and non-epiphyte substrates).
Tree Plots
Substrate
n
Height
n
Alectorioid lichen
32.4 ± 0.5
5
24 ± 1.7
3
Cyanolichen and other lichen
31.8 ± 0.2
19
18.4 ± 0.3
12
---
---
8.5 ± 0.2
11
All Epiphyte Substrates
31.9 ± 0.1
24
14.3 ± 0.1
26
Foliage (live and dead foliage)
30.5 ± 0.1
27
18 ± 0.1
57
Bark
27.4 ± 0.4
9
10.9 ± 0.1
28
Dead Wood
27.3 ± 0.7
4
21.3 ± 1
4
All Phorophyte Substrates
28.9 ± 0.1
42
15.7 ± 0
94
All Substrates*
29.9 ± 0
67
16 ± 0
125
Comparison1
t = 1.22, df = 65, P = 0.27
Epiphyte
Height
Phorophyte
1
Walking Transects
Bryophyte
t = -0.71, df = 116, P = 0.48
Student’s t-test, cumulative “epiphyte” and “phorophyte” comparison by survey type, = 0.05
In the Tree Plots, OS generally foraged higher in the tree canopy when using phorophyte
substrates, relative to epiphytes, although the difference was not statistically significant (P = 0.08).
Similarly, the Walking Transects captured OS foraging at similar heights during bouts on both
67
epiphyte (18 m) and phorophyte substrates (19 m, Table 29). Tree Plot and Walking Transect
differences were apparent: heights recorded for foliage, bark, and all epiphyte substrates (except
“bryophyte” substrates) were higher in the Tree Plots. Gray Jays, which accounted for 94% of all
OS foraging activities in the Tree Plots, used the mid canopy when foraging on both epiphytic and
host resources but showed a shift to the lower canopy when using bryophytes. This trend was
consistent in the Walking Transects. Gray Jays were documented foraging significantly higher on
host resources in the Tree Plots, as compared with foraging data from the Walking Transects (t =
4.06, df = 70, P < 0.001). However, no between-survey procedure differences were found when
epiphyte resources were used (t = 1.59, df = 34, P = 0.06).
Although the Winter Wren was observed foraging on other lichens at 3.3 m above the
ground, the LUHI foraged exclusively in the understory. Dark-eyed Juncos concentrated most
foraging activity in the low understory but were detected higher in the canopy when searching and
gleaning prey items from lichen substrates, namely alectorioid lichens and the foliose lichen, L.
oregana, at 23 m and 18 m, respectively. The two pecking records of Dark-eyed Juncos foraging
on Dicranum and Isothecium mosses occurred on a horizontal bole, and branch of a suppressed T.
heterophylla at 0.7 m and 3 m, respectively.
Table 29: Mean omnivore scavenger foraging heights (m SE), and sample size (n) by substrate
and survey procedure (* includes non phorophyte and non-epiphyte substrates).
Tree Plots
Substrate
Height
n
Height
n
33 ± 0.5
3
34.6 ± 0.8
5
Cyanolichen and other lichen
33.3 ± 0.4
9
21.9 ± 0.6
7
Bryophyte
7.1 ± 0.5
4
9.5 ± 0.3
12
All Epiphyte Substrates
26.7 ± 0.2
16
18.4 ± 0.2
24
Foliage (live and dead foliage)
37 ± 0.2
21
23.3 ± 0.3
13
Bark
31 ± 0.6
3
8.8 ± 0.3
11
Dead Wood
30.1 ± 0.4
9
23 ± 0.4
11
All Phorophyte Substrates
33.9 ± 0.1
36
18.7 ± 0.1
35
31.7 ± 0.1
52
18.3 ± 0.1
63
Phorophyte
Epiphyte
Alectorioid lichen
All Substrates*
Comparison1
1
Walking Transects
t = -1.78, df = 50, P = 0.08
t = -0.07, df = 57, P = 0.94
Student’s t-test, cumulative “epiphyte” and “phorophyte” comparison by survey type, = 0.05
68
When all tree classes were considered for five bird species (e.g., Brown Creeper, Chestnutbacked Chickadee, Red-breasted Nuthatch, Hairy Woodpecker and Gray Jay), P. menziesii and T.
heterophylla accounted for 93% of all foraging bouts in the Tree Plots, whereas these two tree
species comprised only 63% of the foraging activities in the Walking Transects. More than 75% of
all Gray Jay foraging activities in the Tree Plots occurred in the inner and mid portions of the lower
and upper live crown, although the mid-crown (vertical zone) was used. Gray Jays shifted to the
outer portions of the mid- live crown when using host resources (Appendix D). This shift was not
observed in the Walking Transects: Gray Jays used the horizontal zones equally when foraging on
host resources (Appendix E), but used the upper and lower crown more frequently. In the Tree
Plots, Gray Jays used dominant trees more often than the other tree classes when foraging on
epiphytic substrates (79% of all epiphytic foraging bouts), and 43% of these bouts on epiphytes
occurred on P. menziesii (Appendices F and I). In the Walking Transects, Gray Jays used
suppressed trees more frequently, when using both host and epiphytic resources. In the Walking
Transects, Chestnut-backed Chickadees were observed more frequently in the lower live crown
when foraging on both host and epiphytic resources (Appendix E). The Tree Plots captured
Chestnut-backed Chickadees using intermediate trees slightly more frequently (38%) when
foraging on epiphytic substrates than any of the other classes (Appendix F). In the Walking
Transects, Chestnut-backed Chickadees used dominant trees more often during their foraging bouts
on epiphytes, and more than 30% of their bouts involved co-dominant and intermediate classes.
When foraging on phorophyte resources in the Tree Plots Chestnut-backed Chickadees used
dominant trees more frequently, whereas they used suppressed trees more frequently in the
Walking Transects.
Comparison between Sampling Procedures for Resource Use and Availability
Proportional use of epiphyte and host resources, relative to availability, was compared
among survey procedure for five species (Brown Creeper, Chestnut-backed Chickadees, Hairy
Woodpecker, Gray Jay, and Red-breasted Nuthatch). Epiphyte use ranged from 23% (Redbreasted Nuthatch in the Walking Transects) to 59% (Brown Creeper in the Walking Transects)
(Appendix G). Both sampling procedures showed the five pooled species using epiphytes
disproportionately, relative to the available resource pool, although, the test statistic was greater
with the Walking Transect data (Table 30, Appendix G). The Tree Plots captured the five species
using epiphyte group disproportionately, compared to the Walking Transects (Table 31, Appendix
H). Both sampling procedures showed Chestnut-backed Chickadee and Gray Jay using epiphytes
69
disproportionately (Appendix G). The Walking Transects captured only two of the three BI
members (e.g., Brown Creeper and Hairy Woodpecker) using epiphytes disproportionately
(Appendix G). The third BI member, Red-breasted Nuthatch, showed disproportionate use of
epiphytes in the Tree Plot, but the differences were not statistically significant. Separate analyses
of intra-epiphyte groups by survey procedure showed disproportional use of epiphyte substrates,
but differences were not statistically significant for any of the five species for either sampling
procedure (Appendix H).
Table 30: Relative availability of host and epiphyte resources (g Cm-2) and their proportionate use
(%) by five species by survey procedure.
Resource Pool
Available Resources1 (%)
Foliage
Branches and
Stem Bark
Epiphytes
941 (10.2)
8144 (88.7 )
100 (1.1 )
Survey Procedure2
Proportionate Use
Gadj
Critical
χ2
P
Tree Plots
29.9
34.4
35.7
380.40
5.99
< 0.005
Walking Transects
25.4
41.2
33.5
551.10
5.99
< 0.005
Pooled for five species
27.1
38.6
34.3
930.13
5.99
< 0.005
1
Estimated stores of carbon associated with live biomass (Harmon et al. 2004), 2 Total foraging
bouts (n): Tree Plots (154), Walking Transects (260) pooled species (414).
Table 31: Relative availability of epiphyte groups (kg ha-1) and their proportionate use (%) by five
species by survey procedure.
Epiphyte Group
Available Resources1 (%)
Alectorioid
lichens
Cyanolichens &
Other lichens
Bryophytes
934 (14.1)
2382 (35.9)
3316 (50.0)
English Name (n)
Proportionate Use
Gadj
Critical
χ2
P
Tree Plots
16.4
74.5
9.1
44.98
5.99
< 0.025
Walking Transects
14.9
35.6
49.4
0.05
5.99
> 0.1
50.7
33.8
16.19
5.99
< 0.05
Pooled for five species
1
15.5
2
McCune 1993, McCune et al. 1997; Total foraging bouts (n): Tree Plots (55), Walking Transects
(57) pooled species (142).
70
Comparison between Sampling Procedures for Community Structure
The MRPP statistics for each run of both survey procedures indicated less heterogeneity
within, and greater heterogeneity between epiphyte groups and substrates, than expected by chance
(Table 32, Appendix P). For both procedures, overall MRPP runs of foraging guilds, species,
crown class, and vertical canopy crown showed within-group similarities, and among-group
dissimilarities. Between survey procedures differences were evident in the MRPP runs of tree
species, tree condition and foraging posture.
Foraging guilds and species: The overall chance-corrected within-species and withinforaging guild agreement statistics for both survey procedures were heavily influenced by LUHI
(Appendix Q). The strongest among-group patterns were observed between LUHI and three
foraging guilds (BI, TFI, and OS). In the Tree Plots, TS showed stronger dissimilarities with LUHI
(A = 0.579, P = 0.009), whereas TFI showed strong dissimilarities with LUHI in the Walking
Transects (A = 0.162, P < 0.001). The OS, BI, and TFI foraging guilds in both survey procedures
showed weak within-group patterns among their foraging behaviors.
Epiphyte groups and finer-scale substrates: Foraging activities on epiphyte substrates
obtained from both survey procedures indicated similar within-group foraging behaviors, and
among-group dissimilarities between bryophyte groups and both lichen groups (Appendix P).
Stronger among-epiphyte group patterns were observed in the Tree Plot data, relative to the
Walking Transects, although relative group comparison ranks were similar. For both survey
methods, the strongest among-group pattern was observed between bryophytes and alectorioid
lichens (A = 0.331 for Tree Plots, A = 0.094 for Walking Transects, P < 0.001), and then between
bryophytes and cyanolichens and other lichens (A = 0.103 for Tree Plots, A = 0.069 for Walking
Transects, P < 0.001). For both survey procedures, foraging activities used on appressed and
pendant bryophyte groups differed considerably when compared with the lichen groups. For
instance, foraging strategies used on foliose and fruticose lichen and appressed bryophytes were
different in the Tree Plots (A = 0.099, P = 0.014); and between foliose lichen and appressed
bryophytes in the Walking Transects (A = 0.147, P < 0.001).
The strongest patterns were found between alectorioid lichens and pendant bryophytes in
the Tree Plots. In the Walking Transects, the strongest patterns were found between foliose and
fruticose lichen and an admixture of lichen and bryophytes. Analogous patterns were obtained
from both survey methods for the comparison with alectorioid lichens and appressed bryophytes (A
71
= 0.222 for Tree Plots, and A = 0.201 for the Walking Transects, P = 0.001). The majority of the
pairwise comparisons of among-lichen and bryophyte finer scale substrates indicated dissimilar
foraging strategies. Conversely, most pairwise comparisons of within-lichen and within-bryophyte
finer scale substrates groups yielded statistics that indicated similar foraging strategies. Pairwise
comparisons of the remaining finer scale epiphyte substrate groups showed broad overlap
suggesting similar foraging strategies employed, or otherwise smaller sample sizes.
Tree species and Crown Class: Use of tree species showed among-survey procedure
differences (Table 32). Use of tree species groups showed a weak pattern in the Tree Plots,
whereas use of tree species in the Walking Transects showed among-tree species differences (A =
0.114, P < 0.001). For both survey procedures, the comparisons of crown classes showed strong
patterns between suppressed trees and all other crown classes. Broad overlapping was observed
within and between dominant, codominant, and intermediate crown classes.
Foraging maneuvers and postures: Comparisons of all foraging maneuvers and postures
indicated commonality in foraging behaviors in both the Tree Plots and Walking Transects (Table
32). Comparisons of foraging postures showed broad overlapping and all results were statistically
insignificant, except one: the comparison between “reach under” and “hopping” (A = 0.113, P =
0.037). Foraging strategies used by LUHI on all substrates and by all guilds on bryophytes
accounted for most of the differences in foraging strategies between the guilds and epiphyte
groups. In the Walking Transects, three foraging postures (hopping, hovering and reaching-up)
showed among group dissimilarity and within group similarity. Reaching up and hovering postures
were used more frequently by the LUHI and AI guilds, respectively, which contributed to amongforaging guild differences.
Tree position and condition: Use of tree position groups showed a stronger pattern in the
Tree Plots, relative to the Walking Transects (Table 32). Statistically significant strong patterns
were obtained from comparisons of two tree position pairs: branchlet versus bole groups (A =
0.129, P < 0.001), dead branch versus bole groups (A = 0.148, P < 0.001).
72
Table 32: Comparison of differences in epiphyte-related foraging strategies by survey procedure
with non-metric Multi-Response Permutation Procedures, based on Sørensen distances; g = number
of groups; A = chance-corrected within-group agreement; P = probability of Type I error for Ho: no
difference between groups. Bonferroni-adjusted significant P-values indicating among group
dissimilarity and within group similarity are highlighted in bold.
Tree Plots
Walking Transects
g
A value
P
A value
P
Major epiphyte groups1
3
0.124
< 0.001
0.102
< 0.001
Finer scale epiphyte groups2
8
0.111
< 0.001
0.151
< 0.001
3
Foraging Guilds (major groups)
7
0.166
< 0.001
0.152
< 0.001
0.144
< 0.001
Foraging Guilds (finer scale groups)3
7
0.159
< 0.001
4
Species (major groups)
13
0.193
< 0.001
0.183
< 0.001
Species (finer scale groups)4
13
0.194
< 0.001
0.167
< 0.001
5
Crown class
4
0.164
< 0.001
0.193
< 0.001
6
Horizontal Crown
3
0.059
0.001
0.049
< 0.001
Vertical Crown7
5
0.099
0.001
0.096
< 0.001
8
Foraging Maneuver
6
0.022
0.109
0.025
0.017
Foraging Posture9
9
0.043
0.038
0.090
< 0.001
Tree Species10
4
0.053
0.004
0.114
< 0.001
11
Tree Condition
2
0.023
0.022
0.092
< 0.001
Tree Position12
5
0.073
< 0.001
0.054
< 0.001
1
2
alectorioid lichens, cyanolichens and other lichens, bryophytes; alectorioid lichen, foliose lichen,
fruticose lichen, fruticose and foliose lichen, pendant bryophyte, appressed bryophyte, other lichen,
bryophyte and lichen; 3 aerial insectivores, bark insectivores, nectarivores, low-understory
herbivore/insectivores, omnivore-scavengers, timber foliage insectivores, timber seed-eaters; 4
Brown Creeper, Chestnut-backed Chickadee; Dark-eyed Junco, Golden-crowned Kinglet, Gray
Jay, Hairy Woodpecker, Hermit Thrush, Pacific-slope Flycatcher, Red-breasted Nuthatch, Red
Crossbill, Rufous Hummingbird, Steller’s Jay, Winter Wren; 5 dominant, codominant, intermediate,
suppressed; 6 inner, middle, outer live crown; 7 above, upper, middle, lower, below live crown; 8
hammer, glean, probe, peck, pluck, search;9 hop, reach under, short flight, perch, hanging, hang
upside-down, lean over/into, reach up, hovering;10 Tsuga heterophylla, Pseudotsuga menziesii,
Abies spp., Others; 11 live, dead; 12 bole, branch, branchlet, foliage, dead foliage.
Groups
Discussion
Foraging data among species and foraging guilds were not equally represented in both the
Tree Plot and Walking Transect surveys. Although neither survey procedure considered any
species or foraging guild as epiphyte specialists and both designated five species as “regular users”,
only three of the five species were in common (Brown Creeper, Gray Jay and Winter Wren). The
Tree Plots showed that Chestnut-backed Chickadees and Red-breasted Nuthatch were “regular
users” of epiphyte groups, whereas the Walking Transects classified both species as “occasional
users/generalist”. The Tree Plots captured Chestnut-backed Chickadee and Red-breasted Nuthatch
using lichens frequently but failed to capture either species using bryophytes. In comparison, the
73
Walking Transects captured both species using bryophytes. The differences between the survey
procedures suggest that observer location influences the determination of foraging substrates.
Sturman’s (1968) study of Chestnut-backed Chickadees concluded that while foraging in conifers
and hardwood forests they selected bare bark surfaces over moss or lichen covered bark. Similarly,
Weikel and Hayes (1999) found Chestnut-backed Chickadees (and Hairy Woodpeckers) selecting
substrates with relatively low epiphyte cover. Despite the differences in stand age, both Sturman’s
(1968) and Weikel and Hayes (1999) studies were ground-based foraging observations, which
might have underestimated the importance of lichens as foraging sites.
Eighty percent of the Tree Plot data were obtained from the canopy level and no sequence
data within the plots were recorded at ground level for 3 of the 20 days. Although the reason for
this was untested, this suggests that the presence of the ground-level observer might have had a
negative influence on lower-canopy and understory bird activity in the Tree Plot viewing arena.
Alternatively, the tree climbing activity might have flushed LUHIs from the viewing arena. Yet,
non-invasive tree climbing techniques allowed the researcher to conduct foraging observations
from the canopy level and capture foraging activities in the mid and upper live crown. Because the
upper 50 to 60% of the crown contains the greatest number of biodiversity elements due to the
increased number of biological niches (Lindenmayer and Franklin 2002), bird foraging activity is
most likely concentrated in the canopy, attributable to more opportunities to procure food items –
an optimized foraging strategy.
The mean height of all foraging birds detected in the Walking Transects was significantly
lower than those recorded in the Tree Plots. The differences in foraging heights captured among
the two sampling procedures raises the question of whether the observed height differences
between procedures might be a function of the person in the canopy thinking they were taller based
on being high versus ground observers thinking the same height was lower. However, this is
unlikely because the mean height of all Tree Plot observations was almost double the mean height
of observations in the Walking Transects. Furthermore, during the training period prior to data
collection, observers were trained with a laser range finder to ensure that ocular height estimates
were within 10% of true height. Likely explanations for height differences among sampling
procedures include the tendency for Walking Transect observers to concentrate on bird activity
occurring in the lower canopy and understory, coupled with the fact that ground-level observers
found it difficult to observe activity and determine the substrate exploited in the mid to upper
canopy due to dense overstory and general obstruction of view. Dense mid-canopy and sometimes
understory foliage limited ground based observers’ ability to see birds or distinguish substrates
used in the mid and upper crowns of larger trees. High-powered binoculars cannot counteract the
visual barriers that face the ground-level observer, and with the height of many dominant trees in
74
the RNA reaching 60 m, it is virtually impossible for the ground-based observer to detect bird
activity and substrate selection in the upper crown.
Foraging data obtained from the Walking Transects indicated that birds used epiphyte
groups in proportion to the epiphyte groups’ availability, whereas data obtained from the Tree Plots
showed that lichens were used more frequently than bryophytes, relative to their availability. I
consider the observed relationships in the Tree Plots to be confounded; explained partially by the
height of the observer (canopy versus ground level), and that epiphytes are vertically stratified in
the forest profile. Canopy height and light transmittance influences the distribution of epiphytes
(Parker 1997, McCune et al. 1997). Bryophytes occur in the lower profile; cyanolichens occur in
the light transition zone, between 15 and 35 m, whereas other lichens are spread throughout the
vertical profile (McCune et al. 1997). The vast majority of behavioral activities collected in the
Tree Plots were obtained by the canopy-level observer (located at a mean height of 31 m), where
bryophytes reach their upper height limit (McCune et al. 1997). The Walking Transect observers
collected foraging data in the lower profile of the forest, where bryophytes are concentrated. This
might explain differences between survey procedures. For example, although the proportionate use
of alectorioid lichens by birds was similar between sampling procedures, the proportionate use of
bryophyte was five times greater in the Walking Transects than the Tree Plots. Conversely, the
Tree Plots recorded birds using cyanolichens and other lichens more frequently than the Walking
Transects. Thus, use of epiphyte substrates for foraging appears to be a function of observer
location, rather than actual resource selection. Similarly, the location of the observer was an
important determinant for recording the height of bird foraging activity.
In summary, surveys from the canopy facilitated foraging observations of bird species in
the mid to upper canopy, but underestimated bird use of bryophytes. Conversely, the Walking
Transects were important for determining which resources were used in the mid to low canopy and
understory, and allowed observers to access a greater proportion of the RNA, and capture foraging
data for more species and individuals, relative to the Tree Plots. Thus, a combination of canopyand ground-level survey procedures facilitated a more comprehensive assessment of species
richness, increased sample sizes necessary for statistical vigor, and provided a more comprehensive
assessment of epiphyte use throughout the forest’s vertical profile.
75
Subsection 2
Comparison between Canopy- and Ground-Level Point Counts
Thirty-six species were detected during the 20 point counts. When all detections
(including flyovers) were considered, the canopy-level observer detected one more species than the
ground level, although both locations recorded 27 species in common (Appendices R and S). Of
33 total species detected by the canopy-level observer, five species were not detected by the
ground-level observer (Common Raven, Western Tanager, Olive-sided Flycatcher, Purple Finch
and Western Wood-Pewee) (Appendices R and S). Conversely, four of the 32 total species
recorded by the ground-level observer, were undetected by the canopy-level observer (American
Goldfinch, Common Nighthawk, Pileated Woodpecker, and Song Sparrow).
Multiple comparisons of alpha diversity measures in the unlimited-radius plots showed
increased species diversity when counts were conducted at the canopy level, relative to the ground
level (Table 33). Species diversity indices, calculated by plot and survey location in the unlimitedradius plots, showed that the canopy-level observer detected a more species diverse bird
community, and the differences between the ground and canopy species diversity measures were
statistically significant (Shannon’s diversity index: t = 3.67, P = 0.001). Species richness was
greatest with the canopy-level point count data (t = 4.38, P < 0.001). However, both survey
locations showed that the bird community was evenly distributed (Evenness: t = 0.05, P = 0.96).
The rank order of species relative abundance in the unlimited-radius plots was similar between
canopy and ground locations (Wilcoxon Rank Sum Test, z = 0.774, P = 0.44). Similarly, there
was no significant difference in the rank order of species detection between canopy and ground
locations within 75 m (z = -0.523, P = 0.60) and 30 m (z = -0.33, P = 0.74).
Table 33: Species diversity by point count observer location in unlimited-radius plots (all
detections, S = Species richness, E = evenness (H / ln (Richness)), H = Shannon`s diversity index).
Observer Location
Mean SE
S (total)
E
H
Canopy
Ground
0.4 0.23
0.27 0.18
8.45 (33)
6.4 (32)
0.92
0.92
1.9
1.61
For both survey locations in the unlimited-radius-plots, the most frequently detected
species was Winter Wren, which occurred in all but two stations. Red-breasted Nuthatch, Pacificslope Flycatcher and Chestnut-backed Chickadee were next most frequently detected species in the
unlimited-radius counts. Winter Wren, followed by Vaux’s Swift (Chaetura vauxi), were the most
76
frequently detected species in the 30 m-fixed radii plots when maximum counts were calculated.
However, the canopy-level location detected more individuals of Vaux’s Swift more often than the
ground-level location. For both survey locations in the unlimited-radius plots, the most abundant
species were Red Crossbill, followed by Winter Wren, whereas the latter species was less abundant
in the 30 m-plots.
Core Species
Relative Abundance: When the nine core species were pooled, the ground-level observer
detected 10 more individuals than the canopy-level observer within 30 m (ANOVA, F = 3.10, df =
19, P < 0.001, Table 34). However, when plot band-width increased from 30 m to 75 m, the
canopy-level observer recorded 93 more individuals (an increase of 258%), compared with the
ground-level observer who detected only 61 more birds (an increase of 133%). The difference
between observers was statistically significant (F = 4.14, P < 0.001). Beyond 75 m, 81 and 49
more birds were detected by canopy and ground-level observers, respectively. The differences in
relative abundance between observers were proportionate when band-width increased from 30 m to
75 m and when band-width increased from 75 m to unlimited: for both increases in band-width,
the canopy-level observer detected significantly more individuals (32) than the ground-level
observer (F = 5.79, P < 0.001). Variability between observers in relative abundance, as measured
by the differences in the mean number of birds detected within 30 m, was greatest for Chestnutbacked Chickadee and Golden-crowned Kinglet (Table 34). In 75 m plots, between-observer
differences in relative abundance were greatest for Brown Creeper, Chestnut-backed Chickadee,
Pacific-slope Flycatcher, and Red-breasted Nuthatch, and smallest for Hermit Warbler and Hermit
Thrush. In unlimited VCPs, variability between observers was greatest for Pacific-slope Flycatcher
and Red-breasted Nuthatch and smallest for Golden-crowned Kinglet and Hermit Thrush.
77
Table 34: Mean number of birds per plot for nine species by observer location (flyovers
excluded).
English Name
Brown Creeper
Chestnut-backed Chickadee
Golden-crowned Kinglet
Gray Jay
Hermit Thrush
Hermit Warbler
Pacific-slope Flycatcher
Red-breasted Nuthatch
Winter Wren
Total birds
Total species
30 m
Canopy
Ground
0.15
0.25
0.40
0.55
0.10
0.25
0
0.10
0.05
0.15
0.05
0.05
0.30
0.2
0.15
0.15
0.60
0.6
1.80
2.30
1.55
1.75
Plot Radius
75 m
Canopy
Ground
0.60
0.4
1.00
0.75
0.35
0.25
0.20
0.35
0.55
0.5
0.15
0.15
1.20
0.9
0.90
0.7
1.50
1.35
6.45
5.35
4.35
3.90
Unlimited
Canopy
Ground
0.65
0.50
1.00
0.75
0.35
0.25
0.50
0.35
0.75
0.65
0.45
0.15
1.30
0.90
1.30
0.75
1.65
1.35
7.95
5.65
5.20
4.10
Detection Frequency: The ground-level observer detected five of nine species more
frequently within 30 m, relative to the canopy-level observer (Table 35). When band width
increased to 75 m from 30 m, mean detection frequency of the nine species increased 30% and
22% for the canopy-level and ground-level observers, respectively. Mean detection frequency for
the nine species beyond 75 m increased 9% for the canopy-level observer compared to an increase
of only 2% for the ground-level observer. Variability between observers in species detection
frequencies, as measured by the differences in the percentage of VCP in which the species was
recorded, was greatest for Chestnut-backed Chickadee, Gray Jay, and Hermit Thrush within 30 m.
Comparatively, variability between observers in detection frequencies was greatest for Brown
Creeper, Chestnut-backed Chickadee, and Golden-crowned Kinglet in 75 m plots, with each of
these species detected 15% more often by the canopy-level observer. Between-observer
differences in detection frequencies in unlimited plots were greatest for Brown Creeper, Chestnutbacked Chickadee, Golden-crowned Kinglet, Gray Jay, Pacific-slope Flycatcher and Red-breasted
Nuthatch. No differences among-plot radii or between observer differences in detection
frequencies were found for Winter Wren. For the canopy-level observer, Gray Jay, Red-breasted
Nuthatch, and then Hermit Warbler were detected more frequently when plot radii exceeded 75 m.
For both ground and canopy-level observers, Pacific-slope Flycatcher and Red-breasted Nuthatch
were detected more frequently within 75 m radius plots, relative to 30 m radius plots. Detections
of Red-breasted Nuthatch by the canopy-level observer continued to increase beyond 75 m.
78
Table 35: Frequency of occurrence of nine bird species by observer location (flyovers excluded).
English Name
Brown Creeper
Chestnut-backed Chickadee
Golden-crowned Kinglet
Gray Jay
Hermit Thrush
Hermit Warbler
Pacific-slope Flycatcher
Red-breasted Nuthatch
Winter Wren
Percentage of VCP in which species was recorded
30 m
75 m
Unlimited
Canopy Ground Canopy Ground Canopy Ground
15
20
50
35
55
40
30
40
65
50
65
50
10
15
30
15
30
15
0
10
20
30
45
30
5
15
40
30
50
40
5
5
15
15
30
15
20
15
65
60
70
60
15
15
60
65
85
70
60
60
90
90
90
90
Detection Distances: I pooled the data for the nine core species and compared the relative
distribution of detection distances between the canopy- and ground-level observers. When
detection frequencies were truncated at 10-m intervals, the canopy-level observer detected
significantly more birds than the ground-level observer (Paired Student t-test, t = 2.20, df = 10, P =
0.02). The pooled data shows that 40% and 91% of all birds detected were within 30 m and 70 m
of the ground-level observer (Fig. 9). In comparison, only 22% and 79% of birds detected were
within 30 m and 70 m of the canopy-level observer. The smoothed polynomial regression lines and
corresponding R2 values were a good fit for the data and showed that detectability declined with
distance more rapidly with the observer on the ground, than it did with the observer in the canopy,
as noted by the bimodal and right-skewed distribution of canopy-level detections (Fig. 9). The
canopy-level detection distances averaged 16 m more than the ground-level observer (Table 36).
With the exception of Winter Wren, the mode detection distance of all nine species was greater at
the canopy-level than the ground-level (Appendix T).
79
Table 36: Comparison of detection distances (m) for nine species by observer location.
English Name
Brown Creeper
Chestnut-backed Chickadee
Golden-crowned Kinglet
Gray Jay
Hermit Thrush
Hermit Warbler
Pacific-slope Flycatcher
Red-breasted Nuthatch
Winter Wren
Total
Observer Location
Mean SE
Mode
Canopy
Ground
Canopy
Ground
Canopy
Ground
Canopy
Ground
Canopy
Ground
Canopy
Ground
Canopy
Ground
Canopy
Ground
Canopy
Ground
Canopy
Ground
46.8 ± 6.5
38.0 ± 7.6
36.8 ± 4.6
25.0 ± 3.4
36.4 ± 5.6
21.3 ± 2.4
96.5 ± 14.8
41.1 ± 6.6
64.4 ± 5.8
57.0 ± 9.0
92.0 ± 20.6
41.7 ± 17.6
49.8 ± 3.6
49.5 ± 3.2
63.9 ± 5.0
50.5 ± 4.7
47.0 ± 4.8
33.7 ± 2.4
56.4 ± 2.6
40.6 ± 2.0
35
20
40
15
35
25
60
50
100
60
200
--70
50
100
60
40
40
60
35
80
A
Number of birds (frequency)
35
30
R2 = 0.7241
25
20
15
R2 = 0.0565
10
5
0
10
20
30
40
50
60
70
80
90
100
More
B
Number of birds (frequency)
35
30
R2 = 0.9173
25
20
15
10
R2 = 0.4039
5
0
10
20
30
40
50
60
70
80
90
100
More
Detection Distance (m)
Figure 9: Histogram of A) canopy-level and B) ground-level observer detection distances (m) for
nine species (Brown Creeper, Chestnut-backed Chickadee, Golden-crowned Kinglet, Gray Jay,
Hermit Thrush, Hermit Warbler, Pacific-slope Flycatcher, Red-breasted Nuthatch and Winter
Wren).
81
Discussion
The results of the VCP point counts are generally consistent with the findings of Shaw et
al. (2002) where more species and individuals were detected in the upper canopy than lower in the
canopy. I recorded a total of 23 species combining the canopy- and ground-level detections within
a 30 m radius. The three year study by Shaw et al. (2002) recorded 29 species from their 30 m
fixed radius point counts which were conducted at three vertical zones while suspended from a
canopy crane’s gondola on the Wind River Canopy Crane Research Facility. Although
simultaneous canopy- and ground-based counts were not conducted from the crane, and are thus
not directly comparable with the methods I describe, the vertical stratification of bird assemblages
is similar to the results from this study. With the exception of Vaux’s Swift and European Starling,
the relative abundance of species detected at the upper and lower levels was similar to my findings.
Winter Wren, Chestnut-backed Chickadee, Brown Creeper, Gray Jay, Golden-crowned Kinglet,
and Pacific-slope Flycatcher comprised the most frequently detected species in their study, and all
were within the top ten most frequently encountered species in this study. An explanation for the
decreased detections of Vaux’s Swift from the crane gondola, relative to the Tree Plot point counts,
might be avoidance of the canopy crane.
Although ground-level based observations resulted in an underestimate of species diversity
and density, and paired observers in closed-canopy forests are more likely to obtain precise density
estimates (Kissling and Garton 2006), the incorporation of canopy- and ground-level observers for
multiple point count stations is logistically restrictive. Where assessments of abundance estimates
among observers have been conducted, most studies have only considered differences in groundbased observers. In open habitats, for instance, observers are known to overestimate up to 122%
the number of birds present in fixed-radius point counts, whereas bird abundances were
underestimated in unlimited-radius counts (Simons et al. 2007). Vocalizing birds are less likely to
be heard when background noises are present (e.g., other singing birds, wind), and when habitat
structure and vegetation are complex. Among-observer estimates of bird abundance in forested
landscapes with complex vegetation structure and background noises are subject to error (DeSante
1986) and estimates may be as low as 3% of the total birds present (Pacifici et al. 2008).
As the ground-level observer must cope with a complex forest structure above him, so too
must a canopy observer cope with a complex forest structure below. Yet, species richness,
detection frequencies and bird abundance of the nine core species were significantly greater for the
canopy-level observer location and between-observer location differences were more pronounced
as distance bands increased in size. That more individuals and species were detected by both
canopy- and ground-level observers in subsequent increasing distance band widths is consistent
82
with Thompson and Schwalbach (1995) who showed that unlimited-radius plots resulted in more
individuals detected than on 70 m than 50 m radius plots. Thompson and Schwalbach (1995) data
were collected by ground-level observers. This suggests that species richness and abundance
estimates (and foraging behaviors) could be better assessed by sampling a higher percentage of the
habitat. Because the vertical distribution of foliage biomass (Van Pelt et al. 2004) and crown
volume (Ishii et al. 2004) in temperate coniferous forests is greatest between 20 and 40 m, data
collection (e.g., point count and foraging data) from within the canopy results in more habitat being
sampled, as compared to ground-based sampling procedures.
Another explanation for the canopy-level observer detecting more birds and more species
is the tendency for observers to detect more birds that vocalize at a similar height of the observer
(Waide and Narins 1988). For instance, ground-level observers in a tropical forest (with a closed
canopy at 22 m) underestimated the population of canopy birds by as much as 46%, and observers
more readily detected species at their mean singing height (Waide and Narins 1988). Although
species mean singing height was not recorded in my study with a closed forest canopy between 50
and 60 m, the canopy-level observer likely detected more birds because bird abundance is greatest
in the forest canopy, relative to the lower forest profile (Shaw et al. 2002). Ground-level observers
recorded 30% fewer species than canopy-level observers in a tropical forest with an average tree
canopy height of 35 to 40 m (Anderson 2009). Intervening foliage prohibits both visual and
auditory detection from the ground level and upper canopy obligate species occurring at 50 m or
higher are beyond the effective detection distance (Reynolds et al. 1980). For example, a Hermit
Warbler vocalizing from the top of the canopy at 50 m above the ground is only 22 m away from
an observer located in the canopy at 40 m. This same Hermit Warbler would be 54 m from a
ground-level observer located directly below the canopy-observer. Following, the canopy-level
observer has a greater probability of detecting this bird, relative to the ground observer. Thus, the
canopy-level observer detected more Hermit Warblers as distance bands increased because Hermit
Warblers males sing exclusively from the canopy and subcanopy (Pearson 1997). Similarly,
Chestnut-backed Chickadees and Red-breasted Nuthatches, which foraged at mean heights of 21 m
and 34 m, respectively, were detected more frequently by the canopy-level observer.
Other possible explanations for between-observer location differences include the variable
detectibility of bird vocalizations and inter-observer variability. Bird song frequencies vary among
species and attenuate differentially according habitat and weather conditions (Waide and Narins
1988, Pacifici et al. 2008). Vegetation and observers (ground-level) have significant effects on
auditory detection probabilities (Pacifici et al. 2008) and low frequency songs attenuate less rapidly
than birds with high frequency songs (Waide and Narins 1988). Low frequency song attenuation
could explain among-species detection distance differences. For example, as band widths
83
increased for both observers, the increase in bird abundance was greatest for Hermit Thrush and
Red-breasted Nuthatch, which have lower frequency songs, relative to the other core species.
Conversely, detection frequencies between observers were similar for Pacific-slope Flycatcher and
Winter Wren which have high frequency songs.
Although 80-90% of bird detections in coniferous forests are by vocalizations (Waide and
Narins 1988), it remains unknown to what extent detection differences between observer location
for the nine core species were due to visual or auditory detection. For instance, I do not know
whether the canopy-level observer recorded more individuals of these nine species because he
observed them more, or heard them more. However, for some species this was evident. The
canopy observer often recorded aerial insectivores and some upper canopy obligate species as
flyovers prior to the ground-level flyover. For this reason, Red Crossbills were not included the
core group because of the initial detection variability between observers. The canopy-level
observer frequently detected Red Crossbills flocks visually flying over the plot before the ground
level-observer detected the same flock by ear once they settled in the fixed plot.
Mean species richness detected from the canopy- and ground-level locations in this study is
less than the mean reported from three old-growth stands surveyed in Douglas-fir forests in the
southern Washington Cascades (Manuwal 1991). My unlimited radius-plots yielded mean species
richness of 8.5 and 6.4, from the canopy and ground levels, respectively. With ground-based point
counts, Manuwal (1991) surveyed three old growth forests with different moisture regimes and
calculated the mean species richness to be 15.0. The cumulative number of species recorded in our
unlimited radius plots was 33 and 32 species, from the canopy- and ground-level locations,
respectively. Manuwal (1991) reported total species richness for the three sites ranging from 22 to
26. That study also consisted of six visits to the same forest stands over a two year period, which
may account for differences between the studies. The size of their point count plots (75 m) does
not lend a direct comparison with our unlimited-radius plots, although distinguishing detection
distances of songbirds accurately at 75 m and beyond is difficult in dense old-growth stands
(Reynolds et al. 1980). Nonetheless, the five most abundant bird species in Manuwal (1991) were
also within the top nine most abundant species detected by both canopy- and ground-level
observers in my study (e.g., Chestnut-backed Chickadee, Golden-crowned Kinglet,
Hermit/Townsend Warbler, Western Flycatcher and Winter Wren). The rank order of the top 20
most abundant species detected within 75 m of the canopy observer was not different from the
species complex in Manuwal’s study (Wilcoxon Signed Rank Sum Test, z = 1.499, P = 0.07).
Conversely, the rank order of the top 20 most abundant species detected within 75 m of the ground
observer was statistically different from Manuwal’s species complex (z = 2.012, P = 0.02). These
data suggest that the canopy-level observer captured a more comprehensive species complex.
84
CHAPTER 5
DISCUSSION
Ecological Roles of Epiphytes for the Bird Community
Epiphytes may add to the available pool of ecological niches provided by the host plant by
increasing the surface area of temperate forest canopies. The foraging rewards offered to birds by
temperate forest epiphytes are not readily observable, compared with the rewards of nectar, pollen
or fruit offered by their vascular epiphyte tropical counterparts (Stiles 1978, Nadkarni and
Matelson 1988, Sillett 1994). However, temperate forest epiphytes, composed almost entirely of
non-vascular plants, do provide insectivorous birds with indirect rewards. Bryophytes and lichens
provide opportunities for arthropods to find refuge, forage, rest, aestivate, and or thermoregulate,
which offer a forage base for foraging birds, which in turn exert a strong selective pressure that
results in the evolution of cryptic coloration and camouflage among invertebrates (Richardson and
Young 1977). Arthropods comprise the vast majority of food items for coniferous forest
insectivores (Marshall et al. 2003) and subsequently other higher trophic levels, which implies that
the functional role of epiphytes is an important component affecting canopy biodiversity
(Schowalter 1989, McCune 1993, Lindenmayer and Franklin 2002). These lichens and bryophytes
also conceal these rewards, requiring specific foraging tactics to capture prey items located within
or alighting upon them. Each epiphyte functional group provides additional strata that increase the
structural and functional diversity of canopy resources, and foraging opportunities for insectivorous
birds. Below I discuss the relationships of each epiphyte functional group and the resources they
provide for insectivorous birds.
Foliose lichens including cyanolichens such as Lobaria oregana and other conspecifics
increase the surface area of the canopy branches and boles and form refugia for arthropods (BehanPelletier and Eamer 2001). The appressed and often curled margins of foliose lichens are
morphologically similar to peeling bark (Figs. 10 - 12). The broad foliose thallus of L. oregana
reaches 20 to 30 cm (McCune and Geiser 1997), and functions as a “catcher’s mitt” in the canopy,
capturing various potential food items, conifer seed and litterfall that might be lost to granivores
and other consumers on the forest floor. Considering the seed rain from T. heterophylla, T. plicata,
and P. menziesii, a considerable amount of seed is likely captured by the tree canopy, either
deposited on branches or dense splays of foliage. I observed these broad foliose thalli of
85
macrolichens and prostrate bryophytes contributing to the maintenance of perched litter in the
canopy (Fig. 11).
Dead, curled leaves suspended above the forest floor form refugia for insects and are
important bird foraging habitat (Remsen and Parker 1984). Similarly, the broad, lobed thalli of
pendant L. oregana and other broad foliose lichens are morphologically analogous to these curled,
dead leaves of the tropics. The curled thalli margins likely provide refugia for arthropods.
Carpenter ants (Camponotus spp.) were often observed beneath the foliose lichen. Nine of all
foraging bouts (1%) captured birds gleaning, pecking or searching Lobaria spp.
Zygodactylous (two toes facing forward and two facing backward) bark insectivores, such
as Brown Creeper and Hairy Woodpecker, are well suited to use these microsites, and inspect
Lobaria spp. thalli which become pendant when large (Fig. 10). Extracting arthropods from these
refugia entails specific foraging behaviors: the bird must hang upside-down or hang sideways on
either the cyanolichen itself or the supporting branch while probing these cavities. This niche is
unavailable to most anisodactylous (three toes facing forward and one facing backward) songbirds,
with the exception of Red-breasted Nuthatch and Chestnut-backed Chickadee. However, some
songbirds (e.g., Gray Jay) with larger bills are able to use the upper portions of the Lobaria
curtains, by extending their heads and reaching under while perched upon a branch. The body
weights of some smaller passerines, such as Chestnut-backed Chickadee and Golden-crowned
Kinglet, enable them to inspect or capture prey from these pendant epiphytic resources by hovering
or hanging briefly.
Alectorioid lichens are known to harbor a species-rich array of arthropods, particularly in
the subclass Oribatida (Behan-Pelletier and Eamer 2001). These alectorioid lichens increase the
number of ecological niches in the upper canopy, and provide suitable prey items for foraging
passerines (Figs. 13 and 14). Alectorioid lichens drape the outer foliage and crowns of old-growth
trees. Alectoria spp., and Bryoria spp. reach lengths of 40 cm, dangling from foliage or branches.
They hang in single strands, in dense mats, or may cloak the outer foliage of T. heterophylla, and
P. menziesii (Fig. 14). It is the latter two conditions that allowed Gray Jay to more readily use this
resource. Unsupported single strands of the weak-stemmed fruticose alectorioid lichens are unable
to sustain the weight of a hanging Gray Jay (70 g), since the cross-section of one Alectoria
sarmentosa strand is approximately 2.5 mm wide (McCune and Geiser 1997). However, several
strands of alectorioid lichens bear the weight of Chestnut-backed Chickadees (9.7 g), enabling
birds to hang, inspect and procure food items from the lichens. Both adult and juvenile Gray Jay
were observed hanging on lichen cloaked foliage in the upper canopy, although observers were
unable to determine whether the individuals procured prey located on the lichens or the tree
86
foliage. Rufous hummingbirds were also observed actively searching alectorioid lichens either for
nest material or for prey such as ticks and mites, which inhabit alectorioid lichens in the canopy
(Behan-Pelletier and Eamer 2001).
Bryophytes: Appressed and pendant mosses, liverworts, and hornworts provide important
community relations offering cryptic opportunities for adult arthropods and their instar larvae
(Rhoades 1995, Shaw 2004). Soil accumulates beneath these dense mats, which provides habitat
for microorganisms and arthropods (Winchester and Ring 1996). In addition to the complex
physical canopy structure provided for by the phorophyte, bryophytes and other epiphytic material
ameliorate microclimate, offering thermal protection from inclement weather, providing arthropods
refuge sites, and suitable aestivation sites for overwintering arthropod adults or larvae (Fig. 15).
Thus, the epiphytes harbor and secure canopy soils, and contribute detritus that provides microhabitat for microorganisms and other smaller arthropods, which in turn provides a forage base for
larger arthropods and other higher trophic levels. Winchester and Ring (1996) reported that these
moss mats support a unique assemblage of arthropods, relative to the forest floor, and they
speculated that disruption or deterioration of these canopy habitats could decrease the biological
diversity of these rich canopy environments. Although specific prey items were not identified in
this study, birds were observed taking larger arthropods that inhabit and forage in and beneath
appressed bryophytes.
Appressed bryophytes on tree limbs might also offer birds opportunities to bathe in the
canopy. One adult Winter Wren male was observed along the Walking Transect perched on
appressed moss (Dicranum spp.) cloaking the bole of a horizontal log that extended over an
ephemeral creek. It was apparently bathing, repeatedly dipping and rubbing his head and plumage
body into the appressed moss, and thereafter preening his flight feathers. After the male left the
area, I discovered that the Dicranum spp. was wet to the touch, saturated by the heavy morning fog.
Although this activity occurred approximately 1.5 meters above the ground, it is likely that moist
bryophytes in the mid upper canopy also provide bathing opportunities for canopy birds. Winter
Wrens are also known to bathe in dew-covered vegetation (Armstrong 1955) and Conures in
Amazonia are known to bathe communally in wet moss mats at 23 m above the forest floor
(Brightsmith 1999). These bryophytes may be considered the temperate counterparts to the water
tanks of tropical bromeliads.
Pendant bryophytes provide some protection against larger-bodied canopy predators and
insectivores, by providing arthropods locations to alight some distance below the supporting branch
where many birds forage and launch their foraging strikes. The pendant and flimsy bryophytes do
not provide stable sites for birds to perch, as do branches or foliage. Thus, arthropods might alight
87
on these pendant bryophytes to avoid predation. However, several bird species can capture these
insects with aerial maneuvers. The Pacific-slope Flycatcher was the most frequently observed
species taking stationary insects from these pendant bryophytes using their characteristic sally,
hover and glean foraging behavior. Another species observed using these pendant bryophytes was
Chestnut-backed Chickadee. They searched the foliage and branches primarily with short-flights
and hops, and occasionally gleaned stationary insects from pendant bryophytes by hovering or
hanging from the bryophytes themselves. Larger bodied birds such as Gray Jay were never
observed hanging on pendant bryophytes, presumably because the bryophytes are unable to sustain
their weight.
In summary, all epiphyte groups appear to increase the surface area of the canopy crown,
increasing the structural diversity and rugosity of the forest canopy. Rugosity is considered a
measure of complexity, or in ecological terms, an indicator of the amount of available habitat
available for colonization by organisms. Thus, with increased shelter and habitat available for
lower trophic levels, these epiphytes provide additional foraging areas for birds. With increased
available surfaces provided by epiphytes, structural diversity increases, and a forest canopy replete
with epiphytes (mature and old-growth stands) has a greater rumple-factor than a young stand
devoid of such arboreal plants. Increased rugosity of forest canopies enables birds to defend
spherical territories, due to the complex forest structure (Sharpe 1996). Simplify the forest
structure, and birds’ territories may have to increase to maintain the same foraging opportunities.
Vertical and horizontal stratification of epiphyte groups in the canopy provide invertebrates
with specific microhabitats and microniches in each strata, dictated by the epiphyte group present:
alectorioid forage lichens in the inner, mid and outer upper crown; bryophytes in the mid and lower
live crown; cyanolichens in the lower canopy; crustose lichens and finely appressed bryophytes in
the interior crown, along the bole; and other lichens in the upper outer crown. These lichens and
other canopy cryptogams increase the number of ecological niches in the upper canopy, and
provide suitable prey items for foraging passerines.
Epiphytes as food: Whether epiphytic mosses or lichens provide PNW forest birds with
high quality food in times of food shortages is unknown. However, these epiphytes provide an
important food source and egg laying sites for invertebrates, on which many birds depend (Gerson
and Seaward 1977). Many lichens contain acids and other anti-herbivory compounds, yet many
invertebrates are lichenophagous, feeding on lichen (Gerson and Seaward 1977). Although birds
rarely consume canopy lichens directly (except during food shortages), birds may play an
important role in keeping these lichenophagous invertebrates in check. Modification or disruption
of these coniferous canopy lichen assemblages and communities could alter arthropod and bird
88
communities, and higher trophic levels (Pettersson et al. 1995, Uliczka 1999). Similar ecological
roles might exist between birds and invertebrates in canopy bryophyte communities.
Epiphyte dispersal limitations and ecological interactions with birds: Factors responsible
for lichen and bryophyte reproduction and dispersal in forest canopies are poorly known, although
epiphytes may be dispersal limited (Rhoades 1995, Peck and McCune 1997, Sillet and Goslin
1999, Lindemeyer and Franklin 2002). In general, canopy cryptogams reproduce in the tree
crowns, either by spore production or asexual fragmentation. Catastrophic storm events and
associated winds facilitate horizontal and upward vertical movements of epiphyte propagules and
spores. For instance, alectorioid and other pendant fruticose lichens disperse mostly by wind
where fragments are cast off and become entangled in nearby limbs. However, canopy lichens and
bryophytes in tropical forests rely on biotic mechanisms for spore and propagule dispersal,
particularly in still-air environments of inner and mid canopy of middle and lower canopy
(Rhoades 1995). Invertebrates (including ants, springtails and mites) disperse lichen soredia
(Gerson and Seaward 1977).
Temperate forest canopy vertebrates, including resident and neotropical migratory birds,
likely function as important agents of dispersal, particularly during inter-catastrophic weather
events. This occurs passively; soredia, spores, and asexual vegetative propagules stick to bird feet,
feathers and beaks, when birds perch, brush by or initiate a foraging strike on lichen or bryophyte
substrates. Alternatively, some birds may use specific strands and fragments (with propagules
attached) from particular species of bryophyte and lichen for nesting substrate. For example, a
study of 50 Chestnut-backed Chickadee nests in British Columbia found that 70% of the nests
contained bryophytes (Dahlsten et al. 2002). For Hutton Vireo, the epiphytic lichen, Ramalina
menziesii was the most abundant material used in 71% of nests studied in California (Davis 1995).
The predominance of the epiphytic lichen was an important factor in the breeding distribution of
Hutton’s vireos.
In this study, I found a Pacific-slope Flycatcher nest on a fractured piece of bark located on
the bole of a P. menziesii at approximately 4 m. The rim of the nest was comprised of tightly
woven strands of a bryophyte, Isothecium spp., and the exterior was decorated with fragments of
Sphaerophorus globosus. Isothecium spp. was prolific on surrounding understory vegetation and
suppressed trees. However none was apparent on the bole of the nest host, besides the nest itself.
Thus, the flycatcher was involved in relocating these fragments of epiphytes and thus acting as
direct dispersal agent. Bryophyte and lichen propagules collected as nesting material might be
moved considerable distances, both horizontally and vertically in the forest profile. Approximately
100 bird species that breed in coniferous forests of Oregon and Washington use either lichen or
89
moss for nesting substrate, which implies that substantial non-vascular plant material biomass is
relocated and redistributed by birds every nesting season. Because birds are able to move greater
distances, relative to their invertebrate counterparts, they are probably more efficient dispersal
vectors aiding in both lichen and bryophyte sexual and asexual reproduction. For example, Gray
Jays defend breeding territories ranging from 41 to 146 ha (Strickland and Ouellet 2002). Biotic
dispersal vectors are also likely more a reliable means for ensuring that propagules are relocated to
suitable substrate, relative to catastrophic events brought about by abiotic elements such as storms
and high winds. Birds move from one branch to another, which increases the likelihood of
“hitchhiking” soredia or propagules finding suitable substrates when the bird next perches. The
epiphytes benefit from having the birds transport their propagules and the birds benefit from nest
concealment and thermal insulation. Following, maximizing or at least maintaining a certain level
of avian diversity in temperate forested landscapes may be a critical component for epiphytes and
birds themselves.
Birds may also provide an increasingly critical ecological service, given the current stand
age distribution of Washington and Oregon forestlands. Many forestlands are matrix lands which
no longer support interconnected canopies. Most non-vascular epiphyte dispersal systems are
adapted to a forested landscape of connected canopies, so canopy epiphyte species may be
vulnerable to landscape changes (Lindemeyer and Franklin 2002). Could birds then ameliorate the
deleterious effects of local or even regional habitat alteration for several dispersal limited
epiphytes? Research in managed boreal forests of northern Europe shows otherwise; Petterson et
al. (1995) suggested that a decline of avian residents is due to diminished foraging habitat quality
through reduced lichen availability. Natural forests harbor greater invertebrate diversity than
managed forests, supporting more complex and diverse higher trophic levels. Thus, managed
forests in North America could suffer similar effects. In addition, large scale disturbances such as
global climate change could potentially have significant effects on both tropical canopy epiphytes
(Nadkarni and Solano 2002), and temperate forest epiphytes, and it is unlikely that birds could
adequately compensate for such dramatic changes.
90
Figure 10: Lobaria oregana at 30 m provide refugia
for canopy arthropods, prey items for canopy birds.
Figure 11: The broad thallus of Lobaria oregana, at
30 m capture seed rain and litterfall.
Figure 12: Platismatia glauca, a foliose lichen
provides habitat for a dipteran at 30 m.
Figure 13: Alectorioid lichens on the bole of
Pseudotsuga menziesii at 26 m.
Figure 14: At 30 m, Alectoria sarmentosa cloaks the
foliage on Tsuga heterophylla.
Figure 15: Appressed and pendant bryophytes cover
the limbs of Taxus brevifolia.
91
Contribution of epiphytes and birds to the nutrient cycles: The contribution of epiphytes to
the nutrient cycle and hydrological regime in forest ecosystems has received much attention (Pike
1978, Coxson and Nadkarni 1995). Formerly considered “nutrient pirates” (Benzing 1981),
epiphytes are now known to significantly alter throughfall, “fertilizing” the forest with additional
minerals that would not be deposited through normal processes of decay. Nutrients for the
biological needs of most canopy epiphytes are allochthonous, derived primarily from atmospheric
inputs of nitrogen. These canopy cryptogams release nutrients through decay, litterfall, and
leachate. In some productive rainforest systems, epiphyte litterfall and leachate may contribute
nitrogen and biomass greater or equal to that provided by the phorophyte (Nadkarni 1983, Rhoades
1995). Furthermore, these releases of water and minerals typically occur during dry periods, which
supplement both the canopy environment and forest floor, long after the last rain (Nadkarni 1984,
1985).
Considering the community interactions of forest fauna with canopy epiphytes lends even
more complexity to the nutrient cycle. Consumption and subsequent excretion of canopy prey
items are redistributed throughout the canopy by birds, which are either retained in the canopy for
use by bacteria, microepiphytes and other microorganisms, or sent to the forest floor by throughfall
and litterfall. Yet, models showing nitrogen fluxes within old-growth conifer canopies of the PNW
fail to include the contribution of nitrogen by birds in these mineral fluxes (Carroll 1980, Rhoades
1995). Birds move constantly either in search of food, nest sites, plucking locations, or to avoid
predators, and in the process deposit fecal matter throughout the canopy. These fecal deposits are
rich in phosphorus, nitrogen, and other trace minerals, which may be sequestered by canopy
cryptogams and perhaps the phorophyte, through specialized mechanisms such as arboreal roots
(Nadkarni 1983).
It appears that birds might play a role in the fertilization process of forest systems, and the
magnitude of such role for each forest would be moderated by bird abundance, site productivity,
and habitat type. Increased stand age alone and associated epiphyte loads might not be the only
important variables responsible for maintaining ecosystem biochemical function. Further study is
needed to measure and quantify fecal input for temperate coniferous forest birds to contribute to
our understanding of birds’ role in the nutrient cycle.
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Study Limitations
This study documented that forest birds use epiphyte resources during the breeding season
but did not address annual or temporal differences (Brennan et al. 2000). Since canopy arthropod
activity is affected by weather extremes and moisture fluctuations, which occur in the canopy
organic matter (Coxson and Nadkarni 1995), so too will the composition and foraging activities of
higher trophic levels that depend on these resources. Although Grubb (1975) reported inclement
weather affecting bird activity downward vertically, winter at the RNA coincides with snowfall and
cooler conditions in the understory, and bird activity shifts to the upper canopy (Shaw et al. 2002).
The interaction of epiphytes and birds in the winter remains unknown.
There was likely some effect of the canopy- and ground-level observers in the Tree Plots,
although this was not quantified. The presence of the ground-level observer walking around the
perimeter of the viewing arena in the Tree Plot could have affected understory and lower canopy
bird activity within the Plot. Perhaps if the ground-level observer remained stationary, and
recorded activities in the viewing arena from one location, more birds might have moved into the
arena. Also, the climbing activity and the “shadow” of the canopy observer could have also
suppressed bird activity in the understory and lower-canopy levels. More birds were observed at
the canopy level than ground level, although this could also be a function of vertical stratification
of bird assemblages in these forests (Shaw et al. 2002). A similar canopy study in the tropics
speculated no effects of the canopy observers due to the close proximity of the observer to several
foraging individuals (Nadkarni and Matelson 1989). This study documented similar accounts of
foraging activities within several meters of the canopy observer (e.g., both adult and fledgling
individuals of Chestnut-backed Chickadee, Red-breasted Nuthatch, and Gray Jay). However, these
bird species are more tolerant of human presence. Thus, the data might bias the foraging records of
these “kulturfolgers”, culture followers (Rosenzweig 2003). Larger-bodied bird species were never
or rarely detected in the Tree Plots. Examples of such skittish birds include Pileated Woodpecker,
Hairy Woodpecker, and Hermit Thrush. Foraging events were recorded for these species along the
Walking Transect but never in the Tree Plots. The majority of the foraging activities in the Tree
Plots and along the Walking Transects did not seem to be affected by the observers.
93
CHAPTER 6
CONCLUSION AND IMPLEMENTATIONS FOR FOREST
MANAGEMENT
Epiphytes as Foraging Habitat
Epiphytes were used as foraging resources by forest birds in an old-growth Pseudotsuga
menziesii/Tsuga heterophylla forest in the southern Washington Cascades. Determining the
ecological roles between birds and epiphytes and the relative use of epiphytes as compared to other
forest structural components (e.g., foliage, bark) lends new insights into the use of a complex forest
canopy. An abundant epiphyte community contributes to bird diversity because it increases the
canopy rugosity, and adds to the structural complexity of the forest canopy, offering non-tree
resources for harboring prey, and providing opportunities for resource specialization.
Understanding both the biotic and abiotic roles of canopy epiphytes and their importance
for forest ecosystems will allow forest managers to implement ecologically sound management.
Quantifying the importance of epiphytes for birds provides scientific justification for implementing
these recommendations. Documenting ecological interactions in the canopy, and understanding the
foraging opportunities afforded by epiphytes is vital for forest managers to manage for maximizing
biodiversity elements. The importance of understanding the roles of bird and canopy epiphytes
include the ability to predict and mitigate impacts to forest structures and functions that result from
loss of epiphytic species, harvesting effects, or alterations in bird or epiphyte communities. For
instance, current forest management objectives in the State of Washington enforce policies that
facilitate a sustainable harvest. Most forests stands in Washington state lands are either selectively
harvested or clear cut around the time that wood production peaks (40 to 80 years of age).
However, epiphyte diversity peaks at forest ages of more than 200 years (McCune 1993).
Therefore, since forests are harvested at a relatively young age where epiphyte communities are
unable to mature, and since birds use these diverse epiphytic communities hosted by old growth,
the ability to maximize species diversity may be compromised.
Another important component of understanding bird and canopy epiphyte interactions is
having the ability to determine seasonal variations and identify their ecological roles with other
trophic levels. For instance, epiphytes may play an important part in providing auxiliary resources
94
not only during the breeding season, but perhaps during the non-breeding season. Some epiphytes
(such as canopy moss mats) support unique arthropod communities (Winchester & Ring 1996), and
birds may rely on these auxiliary resources when their primary food sources are no longer
available. Schowalter and Ganio (1998) showed that four old-growth forest tree species had
distinct arthropod communities and concluded that forests managed for fewer trees reduce
arthropod diversity.
Understanding these roles also has important management implications for restoration
performance standards. An important conservation tenet for forest managers regulating timber
harvest is protecting biodiversity and also sustaining healthy forests. Integrated and comprehensive
ecosystem management programs are necessary to conserve the entire suite of species associated
with particular habitats. Except for the Northwest Forest Plan (USDA and USDI 1994), few
conservation programs have considered the ecological role of epiphytes in their conservation
strategies. Rather, most plans focus on conserving specific habitat important for the target species
(e.g., old-growth forest for the Northern Spotted Owl and Marbled Murrelet). These fine-scale
approaches to conserving “indicator species” assume that preserving target species habitat often
extends preservation to habitat of species other than the target species. However, there are few
mechanisms other than adaptive management procedures associated with the target species that
evaluate whether these assumptions are valid.
Point Counts
Ground-based point counts are considered the best method to calculate and compare
relative abundance and species richness between sites (Ralph et al. 1995). However point counts
are subject to error in complex three-dimensional habitats (DeSante 1986). These counts are used
to calculate species diversity indices, and although these ground-based assessments may
sufficiently account for all bird species present, they may underestimate the true number of
individuals that use the uppermost portions of the canopy, including upper canopy obligate species
which forage at or above the canopy level. Variable circular plot point counts from the canopy
level facilitated a more comprehensive assessment of species abundances and richness, and
canopy-level point counts in unlimited- and fixed-radius plots also accounted for more flyovers,
which are equally as important components of forest bird assemblages as the canopy-dependent
songbirds. Observer location is an important determinant for recording bird foraging height and
activity. This study does not show that point count observers need to access the forest canopy, but
95
managers should recognize that species richness and bird abundances are likely underestimated
when counts are conducted from the ground-level. Furthermore, ground-based point count
assessments may not provide an adequate assessment of occupancy or presence for canopydependent songbirds. I suggest that point counts conducted by paired ground-based observers in
closed-canopy forests are used to obtain precise density estimates (e.g., Kissling and Garton 2006)
because the incorporation of canopy- and ground-level observers for multiple point count stations
is logistically restrictive. The use of remote acoustic equipment located at fixed height intervals
throughout the forest’s vertical profile could also be used to detect forest birds.
Future Research
In some PNW coastal temperate rainforests, every square meter on every tree is occupied
by an epiphyte. These rainforests harbor tremendous epiphyte biomass in the canopy, which may
exceed the leaf biomass of the phorophyte (Coxson and Nadkarni 1995). Canopy mist-netting
studies (Holbrook 2006) with the use of emetics to analyze stomach contents (Sillett 1994) offer
opportunities to determine what prey are being taken by canopy birds. Since epiphyte communities
harbor unique arthropod assemblages, a study that incorporates: 1) foraging observations, 2)
canopy mist netting and use of an emetic, and 3) correlates arthropod abundances by epiphyte
habitat could shed light on the relative contributions of epiphyte-related prey items for the bird
community. Furthermore, forest habitats are dynamic systems which rely on natural disturbance
regimes that alter epiphyte communities, and the interactions between birds and their habitats. If
birds respond positively to silviculture practices that develop and retain structural integrity and
their epiphyte communities, this knowledge of the interactions between these communities would
assist forest managers charged with managing forests for biodiversity or target species.
Conclusions
The literature search increased the geographical range and number of birds known to use
lichens in their nests. In Washington and Oregon, 100 bird species that breed in coniferous forest
use either bryophyte, lichen or mistletoe in their nests. Furthermore, my canopy- and groundbased field surveys showed that almost 30% of all foraging activities involved epiphyte substrates.
Epiphytes significantly increase the inner canopy rugosity and provide important ecological
functions for birds and higher trophic levels. Because macrolichen and bryophyte species richness
96
in PNW temperate forests is considered high relative to tropical forests (Rhoades 1995),
conservation and maintenance of epiphyte forms and habitats is essential in maintaining total
biodiversity of our forest systems. Approximately 65% of the world’s terrestrial taxa occur in
forest ecosystems (Lindenmayer and Franklin 2002). Yet, the vast majority (between 90 and 95%)
of the world’s forests have no formal protection and preservation of coniferous evergreen forests is
relatively low, relative to other habitats in non-tropical forests (Lindenmeyer and Franklin 2002).
The Northwest Forest Plan (USDA and USDI 1994) mandated that forests be managed for
biodiversity. However, establishing reserves does not fully guarantee the long-term viability and
biodiversity of a forest stand. Buffers, connectivity, and provisions of ecological services are
considerations that need to be addressed, particularly if epiphyte peak distributions and abundances
are sought. To provide prime foraging habitat for forest birds, land managers should consider the
epiphyte vegetative community structure within foraging habitat.
In my study, birds used all tree species proportionately as foraging locations, but used tree
species disproportionately when foraging on epiphytes. Thus, forest managers should retain a
diversity of leave tree species and understory trees and shrubs that maximize epiphyte loads and
maintain canopy connections. Aggregate or dispersed tree retention is known to benefit old-growth
dependent lichens (Sillett et al. 2000), and other epiphyte species with dispersal limitations. Forest
practices may include:
1. retaining large live trees with large branches (associated with lichens and bryophytes);
2. retaining dead, decayed snags and logs because these have rich bryophyte
communities;
3. retaining hardwoods such as big-leaf maple (Acer macrophyllum) which support rich
bryophyte communities; and
4. retaining or enhancing diversity of understory vegetation.
Because greater structural complexity supports more invertebrate habitats and epiphyte
communities and because epiphyte communities change with succession and reach their climax in
old-growth stands (McCune 1993), forest managers should implement practices that maintain oldgrowth structural characteristics to enhance bird species communities.
97
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107
APPENDICES
Appendix A: North American and Oregon/Washington breeding birds that use non-vascular plants, Spanish Moss, epiphytic rootlets, or mistletoe
as nesting substrates.
Substrate
Standard Name
English Name
Bryophyte
ANSERIFORMES
SCREAMERS, DUCKS & RELATIVES
ANATIDAE
Anser brachyrhynchus
Anser albifrons
Branta bernicla
Branta canadensis
Cygnus columbianus
Cygnus cygnus
Aythya collaris
Clangula hyemalis
Mergus merganser
Somateria fischeri
Somateria mollissima
PHASIANIDAE
Falcipennis canadensis
Lagopus lagopus
Lagopus muta
Lagopus leucura
Dendragapus obscurus
Tympanuchus phasianellus
GAVIIFORMES
GAVIIDAE
Gavia stellata
SWANS, GEESE & DUCKS
Pink-footed Goose
X
Greater White-fronted Goose
X
Brant
X
Canada Goose
X
Tundra Swan
X
Whooper Swan
X
Ring-Necked Duck
X
Long-Tailed Duck
X
Common Merganser
X
Spectacled Eider
X
Common Eider
X
QUAIL, PHEASANTS & RELATIVES
Spruce Grouse
X
Willow Ptarmigan
X
Rock Ptarmigan
X
White-Tailed Ptarmigan
Blue Grouse
X
Sharp-Tailed Grouse
X
LOONS
LOONS
Red-Throated Loon
X
Lichen
X
X
X
X
X
Spanish
Moss
Epiphytic
Rootlet
Mistletoe
OR/WA
Coniferous
Forest Breeder
no
no
no
no
no
no
no
no
yes
no
no
yes
no
no
no
yes
no
no
108
Substrate
Standard Name
English Name
Bryophyte
Lichen
Gavia pacifica
Gavia immer
PELECANIFORMES
Pacific Loon
X
Common Loon
X
TROPICBIRDS, PELICANS & RELATIVES
PHALACROCORACIDAE
Phalacrocorax penicillatus
Phalacrocorax pelagicus
FALCONIFORMES
CORMORANTS
Brandt’s Cormorant
Pelagic Cormorant
VULTURES, HAWKS & FALCONS
ACCIPITRIDAE
Accipiter cooperii
Aquila chrysaetos
Buteo brachyurus
Buteo lagopus
Buteo lineatus
Buteo platypterus
Buteo swainsoni
Buteogallus anthracinus
Elanoides forficatus
Elanus leucurus
Haliaeetus leucocephalus
Parabuteo unicinctus
GRUIFORMES
HAWKS, OLD WORLD VULTURES & HARRIERS
Cooper’s Hawk
Golden Eagle
X
X
Short-Tailed Hawk
X
X
Rough-Legged Hawk
X
Red-Shouldered Hawk
X
X
Broad-Winged Hawk
X
Swainson’s Hawk
X
Common Black-Hawk
Swallow-Tailed Kite
X
X
White-tailed Kite
X
Bald Eagle
X
Harris’s Hawk
CRANES, RAILS & RELATIVES
ARAMIDAE
Aramus guarauna
GRUIDAE
Grus canadensis
CHARADRIIDAE
Charadrius semipalmatus
LIMPKIN
Limpkin
CRANES
Sandhill Crane
PLOVERS & RELATIVES
Semipalmated Plover
Spanish
Moss
Epiphytic
Rootlet
Mistletoe
OR/WA
Coniferous
Forest Breeder
no
no
X
X
no
no
X
X
yes
yes
no
no
yes
no
no
no
no
no
yes
no
X
no
X
X
X
X
X
no
X
no
109
Substrate
Standard Name
Pluvialis apricaria
Pluvialis dominica
Pluvialis squatarola
SCOLOPACIDAE
Tringa melanoleuca
Tringa flavipes
Actitis macularius
Numenius phaeopus
Numenius tahitiensis
Limosa lapponica
Arenaria interpres
Aphriza virgata
Calidris canutus
Calidris alba
Calidris mauri
Calidris minutilla
Calidris fuscicollis
Calidris bairdii
Calidris maritima
Calidris ptilocnemis
Calidris alpina
Tryngites subruficollis
Limnodromus scolopaceus
Gallinago gallinago
Phalaropus tricolor
Phalaropus lobatus
Phalaropus fulicarius
LARIDAE
Stercorarius pomarinus
English Name
Bryophyte
European Golden-Plover
X
American Golden-Plover
X
Black-bellied Plover
X
SANDPIPERS & RELATIVES
Greater Yellowlegs
X
Lesser Yellowlegs
X
Spotted Sandpiper
X
Whimbrel
X
Bristle-Thighed Curlew
X
Bar-Tailed Godwit
X
Ruddy Turnstone
X
Surfbird
X
Red Knot
Sanderling
Western Sandpiper
X
Least Sandpiper
X
White-Rumped Sandpiper
X
Baird’s Sandpiper
Purple Sandpiper
Rock Sandpiper
X
Dunlin
Buff-Breasted Sandpiper
X
Long-Billed Dowitcher
X
Common Snipe
X
Wilson’s Phalarope
X
Red-Necked Phalarope
X
Red Phalarope
X
SKUAS, GULLS, TERNS & SKIMMERS
Pomarine Jaeger
X
Lichen
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Spanish
Moss
Epiphytic
Rootlet
Mistletoe
OR/WA
Coniferous
Forest Breeder
no
no
no
no
no
no
no
no
no
no
no
no
no
no
no
no
no
no
no
no
no
no
no
no
no
no
no
110
Substrate
Standard Name
English Name
Bryophyte
Stercorarius parasiticus
Stercorarius longicaudus
Larus philadelphia
Larus canus
Larus argentatus
Larus thayeri
Larus glaucoides
Larus hyperboreus
LARIDAE
Larus marinus
Rissa tridactyla
Rissa brevirostris
Rhodostethia rosea
Pagophila eburnea
Sterna caspia
Sterna paradisaea
Sterna aleutica
ALCIDAE
Brachyramphus marmoratus
Brachyramphus brevirostris
Ptychoramphus aleuticus
Cerorhinca monocerata
COLUMBIFORMES
Parasitic Jaeger
X
Long-Tailed Jaeger
X
Bonaparte’s Gull
X
Mew Gull
X
Herring Gull
X
Thayer’s Gull
X
Iceland Gull
X
Glaucous Gull
X
SKUAS, GULLS, TERNS & SKIMMERS
Great Black-Backed Gull
X
Black-Legged Kittiwake
X
Red-Legged Kittiwake
X
Ross’s Gull
X
Ivory Gull
X
Caspian Tern
X
Arctic Tern
X
Aleutian Tern
X
AUKS, MURRES & PUFFINS
Marbled Murrelet
X
Kittlitz’s Murrelet
X
Cassin’s Auklet
X
Rhinoceros Auklet
X
PIGEONS & DOVES
COLUMBIDAE
Patagioenas fasciata
CUCULIFORMES
PIGEONS & DOVES
Band-Tailed Pigeon
CUCKOOS & RELATIVES
CUCULIDAE
Coccyzus americanus
TYPICAL CUCKOOS
Yellow-Billed Cuckoo
Lichen
X
X
X
X
X
X
X
Spanish
Moss
Epiphytic
Rootlet
Mistletoe
OR/WA
Coniferous
Forest Breeder
no
no
no
no
no
no
no
no
no
no
no
no
no
no
no
no
yes
no
yes
no
X
yes
X
no
111
Substrate
Standard Name
English Name
STRIGIFORMES
OWLS
STRIGIDAE
Bubo virginianus
Bubo scandiacus
Glaucidium gnoma
Strix occidentalis
Strix varia
Strix nebulosa
Aegolius acadicus
TYPICAL OWLS
Great Horned Owl
Snowy Owl
Northern Pygmy-Owl
Spotted Owl
Barred Owl
Great Gray Owl
Northern Saw-Whet Owl
CAPRIMULGIFORMES
GOATSUCKERS & RELATIVES
CAPRIMULGIDAE
Chordeiles minor
GOATSUCKERS
Common Nighthawk
APODIFORMES
SWIFTS & HUMMINGBIRDS
APODIDAE
Cypseloides niger
Aeronautes saxatalis
TROCHILIDAE
Cynanthus latirostris
Hylocharis leucotis
Amazilia beryllina
Amazilia yucatanensis
Amazilia violiceps
Lampornis clemenciae
Eugenes fulgens
Calothorax lucifer
Archilochus colubris
Archilochus alexandri
SWIFTS
Black Swift
White-Throated Swift
HUMMINGBIRDS
Broad-Billed Hummingbird
White-Eared Hummingbird
Berylline Hummingbird
Buff-Bellied Hummingbird
Violet-Crowned Hummingbird
Blue-Throated Hummingbird
Magnificent Hummingbird
Lucifer Hummingbird
Ruby-Throated Hummingbird
Black-Chinned Hummingbird
Bryophyte
X
X
X
Lichen
Spanish
Moss
Epiphytic
Rootlet
Mistletoe
X
X
X
X
X
X
X
X
X
X
X
X
X
OR/WA
Coniferous
Forest Breeder
yes
no
yes
yes
yes
yes
yes
yes
yes
yes
X
X
X
X
X
X
X
X
X
no
no
no
no
no
no
no
no
no
yes
112
Substrate
Standard Name
Calypte anna
Calypte costae
Stellula calliope
Selasphorus platycercus
Selasphorus rufus
Selasphorus sasin
English Name
Anna’s Hummingbird
Costa’s Hummingbird
Calliope Hummingbird
Broad-Tailed Hummingbird
Rufous Hummingbird
Allen’s Hummingbird
Bryophyte
Lichen
X
X
X
X
X
X
X
X
X
X
X
Spanish
Moss
Epiphytic
Rootlet
Mistletoe
OR/WA
Coniferous
Forest Breeder
yes
no
yes
yes
yes
yes
TROGONIFORMES
TROGONIDAE
Trogon elegans
TROGONS
Elegant Trogon
PASSERIFORMES
PERCHING BIRDS
TYRANNIDAE
Camptostoma imberbe
Contopus cooperi
Contopus pertinax
Contopus sordidulus
Contopus virens
Empidonax flaviventris
Empidonax alnorum
Empidonax traillii
Empidonax minimus
Empidonax hammondii
Empidonax oberholseri
Empidonax difficilis
Empidonax occidentalis
Empidonax fulvifrons
Sayornis nigricans
Sayornis phoebe
TYRANT FLYCATCHERS
Northern Beardless-Tyrannulet
Olive-Sided Flycatcher
Greater Pewee
Western Wood-Pewee
Eastern Wood-Pewee
Yellow-Bellied Flycatcher
Alder Flycatcher
Willow Flycatcher
Least Flycatcher
Hammond's Flycatcher
Dusky Flycatcher
Pacific-Slope Flycatcher
Cordilleran Flycatcher
Buff-Breasted Flycatcher
Black Phoebe
Eastern Phoebe
X
no
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
no
yes
no
yes
no
no
no
yes
yes
yes
yes
yes
no
no
no
no
113
Substrate
Standard Name
Sayornis saya
Pyrocephalus rubinus
Pitangus sulphuratus
Tyrannus melancholicus
Tyrannus couchii
Tyrannus forficatus
Pachyramphus aglaiae
LANIIDAE
Lanius ludovicianus
Lanius excubitor
VIREONIDAE
Vireo griseus
Vireo flavifrons
Vireo cassinii
Vireo huttoni
Vireo gilvus
Vireo philadelphicus
Vireo olivaceus
Vireo altiloquus
CORVIDAE
Perisoreus canadensis
Cyanocitta stelleri
Cyanocitta cristata
Cyanocorax yncas
Aphelocoma californica
Gymnorhinus cyanocephalus
Nucifraga columbiana
Corvus brachyrhynchos
Corvus caurinus
English Name
Say's Phoebe
Vermilion Flycatcher
Great Kiskadee
Tropical Kingbird
Couch's Kingbird
Scissor-Tailed Flycatcher
Rose-Throated Becard
SHRIKES
Loggerhead Shrike
Northern Shrike
TYPICAL VIREOS
White-Eyed Vireo
Yellow-Throated Vireo
Cassin's Vireo
Hutton’s Vireo
Warbling Vireo
Philadelphia Vireo
Red-Eyed Vireo
Black-Whiskered Vireo
JAYS, MAGPIES & CROWS
Gray Jay
Steller’s Jay
Blue Jay
Green Jay
Western Scrub-Jay
Pinyon Jay
Clark’s Nutcracker
American Crow
Northwestern Crow
Bryophyte
Lichen
Spanish
Moss
X
X
X
X
X
X
X
X
X
X
X
Epiphytic
Rootlet
Mistletoe
OR/WA
Coniferous
Forest Breeder
yes
no
no
no
no
no
no
X
X
X
no
no
X
X
X
X
X
X
X
X
X
no
no
yes
yes
yes
no
yes
no
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
yes
yes
yes
no
yes
yes
yes
yes
yes
114
Substrate
Standard Name
Corvus corax
HIRUNDINIDAE
Tachycineta bicolor
Stelgidopteryx serripennis
PARIDAE
Poecile carolinensis
Poecile atricapillus
Poecile gambeli
Poecile rufescens
Poecile hudsonica
Poecile cincta
Baeolophus inornatus
Baeolophus ridgwayi
Baeolophus bicolor
AEGITHALIDAE
Psaltriparus minimus
SITTIDAE
Sitta carolinensis
Sitta pygmaea
CERTHIIDAE
Certhia americana
TROGLODYTIDAE
Salpinctes obsoletus
Catherpes mexicanus
Thryothorus ludovicianus
Thryomanes bewickii
Troglodytes troglodytes
English Name
Common Raven
SWALLOWS
Tree Swallow
Northern Rough-Winged Swallow
TRUE TITS
Carolina Chickadee
Black-Capped Chickadee
Mountain Chickadee
Chestnut-Backed Chickadee
Boreal Chickadee
Gray-Headed Chickadee
Oak Titmouse
Juniper Titmouse
Tufted Titmouse
LONG-TAILED TITS
Bushtit
NUTHATCHES
White-Breasted Nuthatch
Pygmy Nuthatch
HOLARCTIC TREECREEPERS
Brown Creeper
WRENS
Rock Wren
Canyon Wren
Carolina Wren
Bewick’s Wren
Winter Wren
Bryophyte
Lichen
Spanish
Moss
Epiphytic
Rootlet
Mistletoe
OR/WA
Coniferous
Forest Breeder
X
yes
X
X
yes
yes
X
X
X
X
X
X
X
X
X
X
no
yes
yes
yes
yes
no
yes
yes
no
X
X
X
X
X
yes
yes
X
X
yes
X
X
X
X
X
X
X
X
yes
yes
yes
no
yes
yes
115
Substrate
Standard Name
English Name
Bryophyte
Lichen
CINCLIDAE
DIPPERS
Cinclus mexicanus
REGULIDAE
Regulus satrapa
Regulus calendula
SYLVIIDAE
Phylloscopus borealis
Polioptila caerulea
Polioptila melanura
TURDIDAE
Luscinia svecica
Oenanthe oenanthe
Sialia mexicana
Myadestes townsendi
Catharus fuscescens
Catharus minimus
Catharus bicknelli
Catharus ustulatus
Catharus guttatus
Turdus pilaris
Turdus iliacus
Turdus migratorius
Ixoreus naevius
TIMALIIDAE
Chamaea fasciata
STURNIDAE
Sturnus vulgaris
American Dipper
X
KINGLETS
Golden-Crowned Kinglet
X
Ruby-Crowned Kinglet
X
OLD-WORLD WARBLERS & GNATCATCHERS
Arctic Warbler
X
Blue-Gray Gnatcatcher
Black-Tailed Gnatcatcher
THRUSHES
Bluethroat
X
Northern Wheatear
X
Western Bluebird
X
Townsend’s Solitaire
X
Veery
X
Gray-Cheeked Thrush
X
Bicknell’s Thrush
X
Swainson’s Thrush
X
Hermit Thrush
X
Fieldfare
X
Redwing
X
American Robin
X
Varied Thrush
X
BABBLERS
Wrentit
STARLINGS & ALLIES
European Starling
X
Spanish
Moss
Epiphytic
Rootlet
Mistletoe
OR/WA
Coniferous
Forest Breeder
yes
X
X
yes
yes
X
X
no
yes
no
X
no
no
yes
yes
yes
no
no
yes
yes
no
no
yes
yes
X
yes
X
yes
X
X
X
X
X
X
116
Substrate
Standard Name
MOTACILLIDAE
Motacilla alba
Anthus cervinus
Anthus rubescens
BOMBYCILLIDAE
Bombycilla garrulus
Bombycilla cedrorum
PTILOGONATIDAE
Ptilogony spp.
Phainopepla nitens
PEUCEDRAMIDAE
Peucedramus taeniatus
PARULIDAE
Vermivora bachmanii
Vermivora celata
Vermivora ruficapilla
Vermivora virginiae
Parula americana
Parula pitiayumi
Dendroica magnolia
Dendroica tigrina
Dendroica caerulescens
Dendroica coronata
Dendroica nigrescens
Dendroica virens
Dendroica townsendi
Dendroica occidentalis
Dendroica fusca
English Name
Bryophyte
WAGTAILS & PIPITS
White Wagtail
Red-Throated Pipit
American Pipit
WAXWINGS
Bohemian Waxwing
Cedar Waxwing
SILKY-FLYCATHERS
Silky Flycatcher
Phainopepla
OLIVER WARBLER
Olive Warbler
WOOD WARBLERS & RELATIVES
Bachman’s Warbler
Orange-Crowned Warbler
Nashville Warbler
Virginia’s Warbler
Northern Parula
Tropical Parula
Magnolia Warbler
Cape May Warbler
Black-Throated Blue Warbler
Yellow-Rumped Warbler
Black-Throated Gray Warbler
Black-Throated Green Warbler
Townsend’s Warbler
Hermit Warbler
Blackburnian Warbler
Lichen
Spanish
Moss
Epiphytic
Rootlet
Mistletoe
OR/WA
Coniferous
Forest Breeder
X
X
X
X
no
no
no
X
X
X
no
yes
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
no
no
no
X
X
X
no
yes
yes
no
no
no
no
no
no
yes
yes
no
yes
yes
no
117
Substrate
Standard Name
Dendroica dominica
Dendroica kirtlandii
Dendroica striata
Dendroica cerulea
Setophaga ruticilla
Protonotaria citrea
Helmitheros vermivorum
Limnothlypis swainsonii
Seiurus aurocapilla
Seiurus noveboracensis
Seiurus motacilla
Oporornis agilis
Geothlypis trichas
Wilsonia citrina
Wilsonia pusilla
Wilsonia canadensis
THRAUPIDAE
Piranga rubra
Piranga ludoviciana
EMBERIZIDAE
Pipilo aberti
Spizella arborea
Pooecetes gramineus
Amphispiza bilineata
Ammodramus savannarum
Passerella iliaca
Melospiza lincolnii
Zonotrichia albicollis
Zonotrichia querula
English Name
Bryophyte
Yellow-Throated Warbler
Kirtland’s Warbler
Blackpoll Warbler
Cerulean Warbler
American Redstart
Prothonotary Warbler
Worm-Eating Warbler
Swainson’s Warbler
Ovenbird
Northern Waterthrush
Louisiana Waterthrush
Connecticut Warbler
Common Yellowthroat
Hooded Warbler
Wilson’s Warbler
Canada Warbler
TANAGERS & HONEYCREEPERS
Summer Tanager
Western Tanager
EMBERIZINES
Abert’s Towhee
American Tree Sparrow
Vesper Sparrow
Black-Throated Sparrow
Grasshopper Sparrow
Fox Sparrow
Lincoln’s Sparrow
White-Throated Sparrow
Harris’s Sparrow
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Lichen
Spanish
Moss
Epiphytic
Rootlet
Mistletoe
X
no
no
no
no
no
no
no
no
no
no
no
no
yes
no
yes
no
X
no
yes
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
OR/WA
Coniferous
Forest Breeder
no
no
no
no
no
yes
no
no
no
118
Substrate
Standard Name
Zonotrichia leucophrys
Zonotrichia atricapilla
Junco hyemalis
Junco phaeonotus
Calcarius mccownii
Calcarius lapponicus
Plectrophenax nivalis
CARDINALIDAE
Cardinalis cardinalis
Passerina cyanea
ICTERIDAE
Euphagus carolinus
Euphagus cyanocephalus
Quiscalus quiscula
Quiscalus mexicanus
Icterus cucullatus
Icterus bullockii
Icterus pectoralis
Icterus gularis
Icterus galbula
FRINGILLIDAE
Fringilla montifringilla
Leucosticte tephrocotis
Leucosticte atrata
Leucosticte australis
Pinicola enucleator
Carpodacus purpureus
Carpodacus cassinii
Loxia curvirostra
English Name
Bryophyte
White-Crowned Sparrow
X
Golden-Crowned Sparrow
X
Dark-Eyed Junco
X
Yellow-Eyed Junco
X
McCown’s Longspur
Lapland Longspur
X
Snow Bunting
X
CARDINALS, GROSBEAKS & ALLIES
Northern Cardinal
Indigo Bunting
BLACKBIRDS, ORIOLES & ALLIES
Rusty Blackbird
X
Brewer’s Blackbird
X
Common Grackle
Great-Tailed Grackle
Hooded Oriole
Bullock's Oriole
X
Spot-Breasted Oriole
Altamira Oriole
Baltimore Oriole
FRINGILLINE FINCHES
Brambling
X
Gray-Crowned Rosy-Finch
X
Black Rosy-Finch
X
Brown-Capped Rosy-Finch
X
Pine Grosbeak
X
Purple Finch
X
Cassin’s Finch
Red Crossbill
X
Lichen
Spanish
Moss
Epiphytic
Rootlet
Mistletoe
yes
no
yes
no
no
no
no
X
X
X
X
X
no
no
X
X
X
X
X
X
X
X
X
X
X
X
X
X
OR/WA
Coniferous
Forest Breeder
no
yes
no
no
no
yes
no
no
no
no
yes
yes
no
yes
yes
yes
yes
119
Substrate
Standard Name
Loxia leucoptera
Carduelis flammea
Carduelis pinus
Carduelis psaltria
Carduelis lawrencei
Coccothraustes vespertinus
English Name
White-Winged Crossbill
Common Redpoll
Pine Siskin
Lesser Goldfinch
Lawrence’s Goldfinch
Evening Grosbeak
Bryophyte
Lichen
X
X
X
X
X
X
X
X
X
X
X
Spanish
Moss
Epiphytic
Rootlet
Mistletoe
X
OR/WA
Coniferous
Forest Breeder
yes
no
yes
yes
no
yes
Sources: Davie, O. (1898), Headstrom, R. (1970), Gabrielson and Jewett (1970); Seward (1977), Ehrlich et al. (1988); Sibley (2000); Marshall et al.
(2003), Baicich and Harrison (2005); Wahl et al. (2005); Cornell Lab of Ornithology (2009); Taxonomy according to American Ornithologists' Union
Checklist of North American Birds - 7th Edition (2005): http://www.aou.org/checklist/index.php3
120
Appendix B: Description of canopy observer height, climbing tree specifics and other associated environmental variables within the Tree Plots’
30m-radius viewing arenas (DBH = diameter at breast height, cm; canopy cover (%) calculated with nine spherical densiometer readings per plot).
Plot
no.a
Canopy
Observer
Height (m)
Tree Species
Climbed (DBH)
MUNA/2
Tag # b
Maximum
DBH (sp)
Maximum
Height (sp)
Aspect
(degrees)
Slope
(%)
Elev.
(m)
Water
Presentc
Canopy
Cover
Survey
Date
7
32.0
PSME (84)
M7-30
96 (PSME)
55 (TSHE)
210
3
329
no
92
26-Apr
11
36.0
ABGR (71)
538
134 (PSME)
45 (ABGR)
150
0.2
347
yes
93
27-Apr
15
31.8
TSHE (105)
M15-2
113 (TSHE)
50 (PIMO)
70
0.6
366
no
92
1-Jun
19
33.9
TSHE (69)
M19-5
181 (PSME)
40 (PSME)
50
12
390
no
94
30-May
25
26.1
TSHE (66)
758
182 (PSME)
40 (THPL)
130
0.1
323
yes
87
27-May
29
28.0
TSHE (79)
946
107 (TSHE)
49 (TSHE)
120
6
335
no
92
23-May
33
31.0
PSME (102)
M33-7
136 (PSME)
60 (PSME)
75
3
347
yes
92
3-May
37
28.0
TSHE (73)
M37-2
125 (PSME)
44 (PSME)
100
5
372
yes
91
5-May
41
25.0
TSHE (79)
M41-1
113 (TSHE)
48 (TSHE)
130
6
396
no
90
11-May
45
30.0
TSHE (72)
1541
107 (PSME)
43 (TSHE)
120
11
433
no
95
12-May
49
31.5
TSHE (71)
M49-13
151 (PSME)
56 (THPL)
140
10
396
yes
89
14-Jun
53
26.0
TSHE (81)
M53-5
139 (PSME)
45 (TSHE)
80
16
433
no
94
7-Jun
57
32.0
TSHE (83)
2037
98 (TSHE)
53 (TSHE)
140
6
475
yes
92
8-Jun
61
42.6
PSME (93)
M61-8
156 (PSME)
69 (PSME)
100
16
408
no
94
15-Jun
65
37.4
TSHE (84)
2342
128 (PSME)
47 (TSHE)
100
17
457
no
92
20-Jun
73
35.3
TSHE (92)
2619
159 (PSME)
43 (TSHE)
100
12
439
yes
89
16-Jun
77
33.5
TSHE (82)
none
137 (PSME)
34 (PSME)
60
11
488
no
93
22-Jun
85
30.5
PSME (93)
none
175 (PSME)
64 (PSME)
110
25
427
no
91
30-Jun
89
31.0
TSHE (77)
M89-6
127 (PSME)
51 (PSME)
115
20
488
no
87
29-Jun
93
Mean
(SD)
Min,
Max
26.1
PSME (92)
3587
114 (PSME)
46 (PSME)
80
24
536
no
75
6-Jul
31.4 (4.4)
82.4 (10.9)
134.9 (2.8)
48.9 (8.6)
25.0, 42.6
66.0, 105.0
107, 182
40, 69
a
These plot numbers correspond to the permanent growth and mortality plots (MUN2 and M UNA of the RNA);
91 (4)
75, 95
b
c
tagged trees within permanent growth plots.; water present in ephemeral stream
121
Appendix C: List of bird species detected in the T. T. Munger Research Natural Area.
STANDARD NAME
ANATIDAE
Branta canadensis1
Mergus merganser
PHASIANIDAE
Bonasa umbellus
ARDEIDAE
Ardea herodias1
CATHARTIDAE
Cathartes aura
ACCIPITRIDAE
Haliaeetus leucocephalus1
Accipiter striatus
Accipiter gentilis
Buteo jamaicensis
COLUMBIDAE
Patagioenas fasciata
STRIGIDAE
Glaucidium gnoma
Strix varia
CAPRIMULGIDAE
Chordeiles minor
APODIDAE
Chaetura vauxi
TROCHILIDAE
Selasphorus rufus
ALCEDINIDAE
Ceryle alcyon
PICIDAE
Sphyrapicus ruber
Picoides villosus
Colaptes auratus
Dryocopus pileatus
TYRANNIDAE
Contopus cooperi
Contopus sordidulus
Empidonax traillii
Empidonax hammondii
Empidonax difficilis
VIREONIDAE
Vireo cassinii
Vireo gilvus
CORVIDAE
Perisoreus canadensis
Cyanocitta stelleri
Corvus corax
ENGLISH NAME
SWANS, GEESE &DUCKS
Canada Goose
Common Merganser
QUAIL, PHEASANTS & RELATIVES
Ruffed Grouse
HERONS & BITTERNS
Great Blue Heron
NEW WORLD VULTURES
Turkey Vulture
HAWKS, OLD WORLD VULTURES & HARRIERS
Bald Eagle
Sharp-shinned Hawk
Northern Goshawk
Red-tailed Hawk
PIGEONS
Band-tailed Pigeon
TYPICAL OWLS
Northern Pygmy-Owl
Barred Owl
NIGHTJARS
Common Nighthawk
SWIFTS
Vaux’s Swift
HUMMINGBIRDS
Rufous Hummingbird
KINGFISHERS
Belted Kingfisher
WOODPECKERS
Red-breasted Sapsucker
Hairy Woodpecker
Northern Flicker
Pileated Woodpecker
TYRANT FLYCATCHERS
Olive-sided Flycatcher
Western Wood-Pewee
Willow Flycatcher
Hammond's Flycatcher
Pacific-slope Flycatcher
TYPICAL VIREOS
Cassin's Vireo
Warbling Vireo
JAYS, MAGPIES & CROWS
Gray Jay
Steller’s Jay
Common Raven
122
STANDARD NAME
HIRUNDINIDAE
Progne subis
Tachycineta bicolor
Tachycineta thalassina
Stelgidopteryx serripennis
Riparia riparia
Hirundo rustica
PARIDAE
Poecile rufescens
SITTIDAE
Sitta canadensis
CERTHIIDAE
Certhia americana
TROGLODYTIDAE
Troglodytes troglodytes
REGULIDAE
Regulus satrapa
Regulus calendula
TURDIDAE
Catharus ustulatus
Catharus guttatus
Turdus migratorius
Ixoreus naevius
STURNIDAE
Sturnus vulgaris
BOMBYCILLIDAE
Bombycilla cedrorum
PARULIDAE
Dendroica coronata
Dendroica nigrescens
Dendroica townsendi
Dendroica occidentalis
Oporornis tolmiei
Geothlypis trichas
Wilsonia pusilla
THRAUPIDAE
Piranga ludoviciana
EMBERIZIDAE
Pipilo maculatus
Spizella passerina
Melospiza melodia
Zonotrichia leucophrys
Junco hyemalis
CARDINALIDAE
Pheucticus melanocephalus
ICTERIDAE
Agelaius phoeniceus
Xanthocephalus xanthocephalus
ENGLISH NAME
SWALLOWS
Purple Martin
Tree Swallow
Violet-green Swallow
Northern Rough-winged Swallow
Bank Swallow
Barn Swallow
TRUE TITS
Chestnut-backed Chickadee.
NUTHATCHES
Red-breasted Nuthatch
HOLARCTIC TREECREEPERS
Brown Creeper
WRENS
Winter Wren
KINGLETS
Golden-crowned Kinglet
Ruby-crowned Kinglet
THRUSHES
Swainson’s Thrush
Hermit Thrush
American Robin
Varied Thrush
STARLINGS & ALLIES
European Starling
WAXWINGS
Cedar Waxwing
WOOD WARBLERS & RELATIVES
Yellow-rumped Warbler
Black-throated Gray Warbler
Townsend’s Warbler
Hermit Warbler
MacGillivray’s Warbler
Common Yellowthroat
Wilson’s Warbler
TANAGERS & HONEYCREEPERS
Western Tanager
EMBERIZINES
Spotted Towhee
Chipping Sparrow
Song Sparrow
White-crowned Sparrow
Dark-eyed Junco
CARDINALS, GROSBEAKS & ALLIES
Black-headed Grosbeak
BLACKBIRDS, ORIOLES & ALLIES
Red-winged Blackbird
Yellow-headed Blackbird
123
STANDARD NAME
Molothrus ater
FRINGILLIDAE
Carpodacus purpureus
Carpodacus cassinii
Loxia curvirostra
Carduelis pinus
Carduelis tristis
Coccothraustes vespertinus
ENGLISH NAME
Brown-headed Cowbird
FRINGILLINE FINCHES
Purple Finch
Cassin’s Finch
Red Crossbill
Pine Siskin
American Goldfinch
Evening Grosbeak
Sources: Taxonomy - American Ornithologists' Union Checklist of North American Birds - Seventh Edition (2005):
http://www.aou.org/checklist/index.php3, 1 = species detected flying/presumably migrating over the RNA only
124
Appendix D: Comparative use of horizontal and vertical tree zones by four birds during foraging
bouts on host and epiphyte substrates, Tree Plots.
Chestnut-backed Chickadee
Chestnut-backed Chickadee
Above crown
outer crown
Upper crown
mid crown
Mid crown
Host (N = 30)
Epiphytes (n = 18)
inner crown
0
20
40
60
80
Host (N = 31)
Epiphytes (N = 21)
Lower crown
0
100
20
40
60
80
100
Percent
Percent
Gray Jay
Gray Jay
Above crown
outer crown
Upper crown
mid crown
Mid crown
Host (N = 28)
inner crown
Host (N = 29)
Epiphytes (N = 12)
0
20
40
60
80
Epiphytes (N = 13)
Lower crown
0
100
20
40
60
80
100
Percent
Percent
Red-breasted Nuthatch
Red-breasted Nuthatch
Above crown
outer crown
Host (N = 17)
Upper crown
Epiphytes (N = 11)
mid crown
Mid crown
Host (N = 16)
inner crown
Epiphytes (N = 9)
0
20
40
60
80
Lower crown
100
0
20
40
60
80
100
Percent
Percent
Red Crossbill
Red Crossbill
Above crown
outer crown
Upper crown
Host (N = 30)
mid crown
Mid crown
Host (N = 30)
Epiphytes (N = 4)
Epiphytes (N = 4)
Lower crown
inner crown
0
20
40
60
Percent
80
100
0
20
40
60
80
100
Percent
125
Appendix E: Comparative use of horizontal (left) and vertical (right) tree zones by six foraging
birds during foraging bouts on host and epiphyte substrates, Walking Transects.
Chestnut-backed Chickadee
Chestnut-backed Chickadee
above live crown
outer crown
Host (N = 57)
upper crown
Epiphytes (N = 20)
mid crown
mid crown
Host (N = 59)
lower crown
Epiphytes (N = 20)
inner crown
below live crown
0
20
40
60
80
100
0
20
Percent
60
80
100
Percent
Gray Jay
Gray Jay
Host (N = 22)
outer crown
40
above live crown
Epiphytes (N = 13)
mid crown
upper crown
mid crown
Host (N = 21)
lower crown
inner crown
Epiphytes (N = 15)
below live crown
0
20
40
60
80
100
0
20
Percent
40
60
80
100
Percent
Red-breasted Nuthatch
Red-breasted Nuthatch
above live crown
outer crown
upper crown
mid crown
mid crown
Host (N = 12)
Epiphytes (N = 5)
inner crown
Host (N = 14)
lower crown
Epiphytes (n = 5)
below live crown
0
20
40
60
80
100
0
20
Percent
80
100
Brown Creeper
above live crown
Host (N = 14)
upper crown
Epiphytes (N = 22)
mid crown
60
Percent
Brown Creeper
outer crown
40
Host (N = 14)
mid crown
Epiphytes (N = 21)
lower crown
inner crown
below live crown
0
20
40
60
Percent
80
100
0
20
40
60
80
100
Percent
126
Appendix E (cont.): Comparative use of horizontal (left) and vertical (right) tree zones by six
foraging birds during foraging bouts on host and epiphyte substrates, Walking Transects.
Hairy Woodpecker
Hairy Woodpecker
above live crown
outer crown
Host (N = 14)
mid crown
Host (N = 10)
upper crown
Epiphyte (N = 5)
Epiphytes (N = 5)
mid crown
lower crown
inner crown
below live crown
0
20
40
60
80
0
100
20
40
60
80
100
Percent
Percent
Pacific-slope Flycatcher
Pacific-slope Flycatcher
above live crown
outer crown
upper crown
Host (N = 25)
mid crown
mid crown
Host (N = 24)
Epiphytes (N = 4)
lower crown
inner crown
Epiphytes (N = 4)
below live crown
0
20
40
60
Percent
80
100
0
20
40
60
80
100
Percent
127
Appendix F: Epiphyte and host use of tree classes by six foraging birds; Tree Plots (left) and Walking Transects (center and right).
Chestnut-backed Chickadee
Chestnut-backed Chickadee
Dominant
Dominant
Co-dominant
Co-dominant
Host (N = 36)
Intermediate
Intermediate
Epiphytes (N = 23)
Suppressed
Host (N = 71)
Epiphytes (N = 24)
Suppressed
0
20
40
60
80
100
0
20
40
Percent
Gray Jay
Host (N = 32)
Intermediate
Epiphytes (N = 14)
Suppressed
20
40
Dominant
Dominant
Co-dominant
Co-dominant
Intermediate
Host (N = 33)
60
80
100
0
20
40
60
Dominant
Co-dominant
Co-dominant
Host (N = 19)
40
60
100
0
20
40
80
80
100
Pacific-slope Flycatcher
Dominant
Co-dominant
Host (N = 19)
Host (N = 27)
Intermediate
Epiphytes (N = 5)
Suppressed
100
60
Percent
Intermediate
Epiphytes (N = 12)
20
80
Red-breasted Nuthatch
Dominant
0
Epiphytes (N = 11)
Suppressed
Percent
Red-breasted Nuthatch
Suppressed
Host (N = 27)
Intermediate
Epiphytes (N = 21)
Percent
Intermediate
100
Hairy Woodpecker
Suppressed
0
80
Gray Jay
Dominant
Co-dominant
60
Percent
Epiphytes (N = 4)
Suppressed
0
20
40
Percent
60
80
100
Percent
Red Crossbill
0
20
40
60
80
100
Percent
Brown Creeper
Dominant
Dominant
Co-dominant
Co-dominant
Intermediate
Host (N = 31)
Suppressed
Epiphytes (N = 4)
0
20
40
60
Percent
80
Host (N = 17)
Intermediate
100
Epiphytes (N = 24)
Suppressed
0
20
40
60
80
100
Percent
128
Appendix G: Relative availability of host and epiphyte resources (g Cm-1) and their proportional
use (%) by five species by survey type.
Resource Pool
Available Resources1 (%)
English Name
Chestnut-backed
Chickadee
Red-breasted
Nuthatch
Gray Jay
Brown Creeper
Hairy
Woodpecker
All five species
1
Foliage
Branches and
Stem Bark
Epiphytes
941 (10.2)
8144 (88.7 )
100 (1.1 )
Survey Type2
(n)
Proportional Use
Gadj
Critical
χ2
P
TP (61)
39.3
21.3
39.3
106.71
3.84
< 0.05
WT (99)
46.5
29.3
24.2
132.59
3.84
< 0.05
Pooled (160)
43.8
26.3
30.0
238.83
3.84
< 0.05
TP (30)
16.7
43.3
40.0
2.92
3.84
> 0.1
WT (26)
23.1
53.8
23.1
9.14
3.84
> 0.1
Pooled (56)
19.6
48.2
32.1
54.91
5.99
< 0.01
TP (48)
35.4
35.4
29.2
79.85
5.99
< 0.01
WT (56)
23.2
37.5
39.3
89.41
5.99
< 0.01
Pooled (104)
28.8
36.5
34.6
170.20
5.99
< 0.005
TP (10)
0.0
70.0
30.0
4.16
5.99
> 0.1
WT (41)
2.4
39.0
58.5
78.21
5.99
< 0.01
Pooled (51)
2.0
45.1
52.9
77.29
5.99
< 0.01
TP (5)
0.0
60.0
40.0
*
*
*
WT (38)
0.0
71.1
28.9
20.48
5.99
< 0.025
Pooled (43)
0.0
69.8
30.2
23.66
5.99
< 0.025
TP (154)
29.9
34.4
35.7
380.40
5.99
< 0.005
WT (260)
25.4
41.2
33.5
551.10
5.99
< 0.005
Pooled (414)
27.1
38.6
34.3
930.13
5.99
< 0.005
2
Estimated stores of carbon associated with live biomass (Harmon et al. 2004; TP = Tree Plots,
WT = Walking Transects; * not enough data.
129
Appendix H: Relative availability of epiphyte groups (kgha-1) and their proportional use (%) by
five species by survey type.
Epiphyte Group
Available Resources1 (%)
English Name
Chestnut-backed
Chickadee
Red-breasted
Nuthatch
Gray Jay
Brown Creeper
Hairy
Woodpecker
All five species
1
Alectorioid
lichens
Cyanolichens &
Other lichens
Bryophytes
934 (14.1)
2382 (35.9)
3316 (50.0)
Survey
Type2 (n)
Proportional Use
Gadj
Critical
χ2
P
TP (24)
20.8
79.2
0.0
18.41
3.84
> 0.05
WT (24)
12.5
41.7
45.8
0.33
3.84
> 0.1
Pooled (48)
16.7
60.4
22.9
15.53
5.99
< 0.05
TP (12)
8.3
91.7
0.0
15.87
3.84
> 0.05
WT (6)
16.7
50.0
33.3
*
*
*
Pooled (18)
11.1
77.8
11.1
12.06
3.80
> 0.05
TP (14)
21.4
50.0
28.6
2.56
3.84
> 0.1
WT (22)
22.7
31.8
45.5
0.18
3.84
> 0.1
Pooled (36)
22.2
38.9
38.9
2.44
5.99
> 0.1
TP (3)
0.0
66.7
33.3
*
*
*
WT (24)
16.7
33.3
50.0
0.15
3.84
> 0.1
Pooled (27)
14.8
37.0
48.2
0.04
5.99
> 0.1
TP (2)
0.0
100.0
0.0
*
*
*
WT (11)
0.0
27.3
72.7
2.26
3.84
> 0.1
Pooled (13)
0.0
38.5
61.5
3.67
3.84
> 0.1
TP (55)
16.4
74.5
9.1
44.98
5.99
< 0.025
WT (87)
14.9
35.6
49.4
0.05
5.99
> 0.1
Pooled (142)
15.5
50.7
33.8
16.19
5.99
< 0.05
2
McCune 1993, McCune et al. 1997; TP = Tree Plots, WT = Walking Transects; * not enough
data.
130
Appendix I: Availability of tree species (%) and their proportional use (%) by five species
during foraging bouts on epiphyte substrates.
Species
1
CBCH
RBNU
GRAJ
BRCR
HAWO
All five
species
Survey
Type2 (n)
Gadj
Critical
χ2
P
ABSP
PSME
TSHE
THPL
OTHERS
TP (24)
0
33.3
66.7
0
0
0.49
3.84
> 0.1
WT (24)
16.7
16.7
45.8
0
20.8
2.16
5.99
> 0.1
Pooled (48)
8.3
25
56.3
0
10.4
3.17
7.82
> 0.05
TP (12)
8.3
8.3
75.0
0.0
8.3
0.92
3.84
> 0.1
WT (6)
0.0
16.7
50.0
0.0
33.3
*
*
*
Pooled (18)
5.6
11.1
66.7
0.0
16.7
2.43
3.84
> 0.1
TP (14)
7.1
42.9
42.9
0.0
7.1
1.55
3.84
> 0.1
WT (22)
4.5
9.1
54.5
0.0
31.8
0.001
3.84
> 0.1
Pooled (36)
5.6
22.2
50.0
0.0
22.2
0.97
5.99
> 0.1
0
25
75
0
0
*
*
*
WT (24)
12.5
4.2
70.8
0.0
12.5
5.78
5.99
> 0.05
Pooled (27)
11.1
11.1
66.7
0.0
11.1
1.56
5.99
> 0.1
0
50
50
0
0
*
*
*
WT (11)
27.3
18.2
18.2
0.0
36.4
6.04
3.84
> 0.1
Pooled (13)
23.1
23.1
23.1
0.0
30.8
6.06
3.84
> 0.1
TP (55)
3.6
30.9
61.8
0.0
3.6
15.93
7.82
< 0.025
WT (87)
12.6
11.5
51.7
0.0
24.1
8.19
7.82
< 0.05
Pooled (142)
9.2
19.7
54.9
0.0
16.2
5.85
7.82
< 0.05
57
(14.73)
56
(13.79)
56.5
(14.25)
60
(15.5)
72
(17.73)
66
(16.65)
231
(59.69)
223
(54.93)
227
(57.25)
10 (2.58)
29 (7.49)
14 (3.45)
41 (10.1)
12 (3.03)
35 (8.83)
TP (3)
TP (2)
TP (24)
Available
Resources4
# trees (%)
Tree Species3
WT (24)
Pooled (48)
1
CBCH = Chestnut-backed Chickadee, RBNU = Red-breasted Nuthatch, GRAJ = Gray Jay,
BRCR = Brown Creeper, HAWO = Hairy Woodpecker;2 TP = Tree Plots, WT = Walking
Transects ; 3 ABSP = Abies spp., PSME = Pseudotsuga menziesii, TSHE = Tsuga heterophylla,
THPL = Thuja plicata; 4 Data were provided by the Permanent Study Plot program, a partnership
between the H.J. Andrews Long-Term Ecological Research program and the U.S. Forest Service
Pacific Northwest Research Station, Corvallis, OR.; * not enough data.
131
Appendix J: Multi-response permutation procedures (MRPP) pairwise comparisons by epiphyte
foraging activity, data pooled (N = 191). Bonferroni-adjusted significant P-values indicating
among group dissimilarity and within group similarity are highlighted in bold.
Groups
Major Epiphyte Groups
alectorioid lichen vs. bryophytes
alectorioid lichen vs. cyanolichen & other lichen
alectorioid lichen vs. lichen/bryophyte admixture
bryophyte vs. cyanolichen & other lichen
bryophyte vs. lichen/bryophyte admixture
cyanolichen & other lichen vs. lichen/bryophyte admixture
Finer-Scale Epiphyte Groups
alectorioid lichen vs. foliose and fruticose lichen
appressed bryophyte vs. alectorioid lichen
appressed bryophyte vs. foliose and fruticose lichen
appressed bryophyte vs. foliose lichen
appressed bryophyte vs. lichen/bryophyte admixture
appressed bryophyte vs. pendant bryophyte
foliose lichen vs. alectorioid lichen
foliose lichen vs. foliose and fruticose lichen
foliose lichen vs. pendant bryophyte
fruticose lichen vs. alectorioid lichen
fruticose lichen vs. appressed bryophyte
fruticose lichen vs. foliose and fruticose lichen
fruticose lichen vs. foliose lichen
fruticose lichen vs. lichen/bryophyte admixture
fruticose lichen vs. pendant bryophyte
lichen/bryophyte admixture vs. alectorioid lichen
lichen/bryophyte admixture vs. foliose and fruticose lichen
lichen/bryophyte admixture vs. foliose lichen
lichen/bryophyte admixture vs. pendant bryophyte
other lichen vs. alectorioid lichen
other lichen vs. appressed bryophyte
other lichen vs. foliose and fruticose lichen
other lichen vs. foliose lichen
other lichen vs. fruticose lichen
other lichen vs. lichen/bryophyte admixture
other lichen vs. pendant bryophyte
pendant bryophyte vs. alectorioid lichen
pendant bryophyte vs. foliose and fruticose lichen
Pooled Data (N = 191)
A value
P - value
0.177
< 0.001
0.155
< 0.001
0.002
0.276
0.088
0.003
0.169
< 0.001
0.007
0.132
0.025
0.005
0.215
< 0.001
0.012
0.135
0.264
< 0.001
0.268
< 0.001
0.254
< 0.001
0.046
0.010
0.045
< 0.001
0.003
0.268
-0.002
0.466
0.172
< 0.001
0.017
0.150
0.108
< 0.001
0.032
0.104
0.008
0.188
0.009
0.152
0.054
0.001
0.088
0.003
0.167
< 0.001
0.053
0.003
-0.001
0.438
0.059
0.007
0.084
< 0.001
0.118
0.001
0.061
< 0.001
0.053
0.058
0.012
0.284
0.030
0.010
0.168
< 0.001
0.183
< 0.001
Guilds (see Appendix K for pairwise comparison )
0.178
< 0.001
Species (see Appendix L for pairwise comparison)
0.231
< 0.001
132
Groups
Crown class
codominant vs. dominant
codominant vs. intermediate
codominant vs. suppressed
dominant vs. intermediate
dominant vs. suppressed
suppressed vs. intermediate
Horizontal Crown
Vertical Crown
below live crown vs. above live crown
lower live crown vs. above live crown
lower live crown vs. below live crown
lower live crown vs. upper live crown
mid live crown vs. above live crown
mid live crown vs. below live crown
mid live crown vs. lower live crown
mid live crown vs. upper live crown
upper live crown vs. above live crown
upper live crown vs. below live crown
Foraging Maneuver
Foraging Posture
hang upside-down vs. hover
hang upside-down vs. reach under
hang upside-down vs. short flight
hang upside-down vs. stand
hang upside-down vs. walk/run
hang vs. hang upside-down
hang vs. hop
hang vs. hover
hang vs. lean over or into
hang vs. perch
hang vs. reach under
hang vs. short flight
hang vs. stand
hang vs. walk/run
hop vs. hang upside-down
hop vs. hover
hop vs. lean over or into
hop vs. reach under
hop vs. short flight
hop vs. stand
hop vs. walk/run
hover vs. reach under
Pooled Data (N = 191)
A value
P - value
0.225
< 0.001
0.011
0.045
0.015
0.029
0.278
< 0.001
0.508
< 0.001
0.229
< 0.001
0.159
< 0.001
0.063
< 0.001
0.149
< 0.001
0.298
< 0.001
0.123
< 0.001
0.030
0.002
0.076
< 0.001
0.050
0.002
0.171
< 0.001
0.081
< 0.001
0.011
0.106
0.039
0.051
0.183
< 0.001
0.038
0.001
0.105
<0.001
0.022
0.169
-0.032
0.824
0.009
0.346
0.418
0.000
0.345
0.000
0.015
0.054
0.029
0.012
0.029
0.012
0.026
0.018
0.009
0.054
-0.006
0.690
-0.001
0.447
0.116
0.000
0.072
0.000
0.116
0.002
0.145
0.003
0.094
0.012
0.034
0.173
0.007
0.361
0.189
0.005
0.117
0.044
0.004
0.407
133
Groups
hover vs. short flight
hover vs. stand
hover vs. walk/run
lean over or into vs. hang upside-down
lean over or into vs. hover
lean over or into vs. reach under
lean over or into vs. short flight
lean over or into vs. stand
lean over or into vs. walk/run
perch vs. hang upside-down
perch vs. hop
perch vs. hover
perch vs. lean over or into
perch vs. reach under
perch vs. short flight
perch vs. stand
perch vs. walk/run
reach under vs. short flight
reach under vs. stand
reach under vs. walk/run
short flight vs. walk/run
stand vs. short flight
stand vs. walk/run
Tree Species
TSHE vs. Ground, Log or Other
TSHE vs. ABSP
TSHE vs. ACCI and TABR
TSHE vs. PSME
TSHE vs. PIMO, THPL or SNAG
Ground, Log or Other vs. ABSP
Ground, Log or Other vs. ACCI and TABR
Ground, Log or Other vs. PSME
Ground, Log or Other vs. PIMO, THPL or SNAG
ABSP vs. ACCI and TABR
ABSP vs. PSME
ABSP vs. PIMO, THPL or SNAG
ACCI and TABR vs. PSME
ACCI and TABR vs. PIMO, THPL or SNAG
PSME vs. PIMO, THPL or SNAG
Tree Condition (live versus dead)
Tree Position
bole vs. branch
bole vs. dead branch/let
Pooled Data (N = 191)
A value
P - value
0.086
0.078
0.464
0.000
0.420
0.002
0.048
0.052
0.028
0.161
0.007
0.357
0.083
0.069
0.273
0.003
0.264
0.006
0.024
0.019
0.012
0.081
0.043
0.002
0.026
0.018
-0.001
0.415
0.001
0.385
0.095
0.000
0.057
0.001
-0.055
0.687
0.457
0.002
0.482
0.014
0.608
0.023
0.578
0.002
0.282
0.024
0.215
<0.001
0.181
<0.001
0.022
0.003
0.154
<0.001
0.019
0.004
0.011
0.044
0.199
<0.001
0.119
<0.001
0.392
<0.001
0.314
<0.001
0.082
<0.001
0.106
<0.001
0.081
0.012
0.333
<0.001
0.222
<0.001
0.017
0.100
0.081
< 0.001
0.108
<0.001
0.047
<0.001
0.059
<0.001
134
Groups
branch vs. dead branch/let
branchlet vs. bole
branchlet vs. branch
branchlet vs. dead branch/let
branchlet vs. foliage
foliage vs. bole
foliage vs. branch
foliage vs. dead branch/let
Pooled Data (N = 191)
A value
P - value
0.014
0.031
0.178
<0.001
0.093
<0.001
0.049
0.001
-0.001
0.428
0.142
<0.001
0.071
<0.001
0.041
0.008
Appendix K: Multi-response permutation procedures pairwise comparisons of foraging guilds
by epiphyte foraging activity, data pooled (N = 191). Bonferroni-adjusted significant P-values
indicating among group dissimilarity and within group similarity are highlighted in bold.
Groups
bark insectivore vs. nectarivore
timber-foliage insectivore vs. nectarivore
omnivore/scavenger vs. nectarivore
timber-foliage insectivore vs. omnivore/scavenger
bark insectivore vs. aerial insectivore
bark insectivore vs. omnivore/scavenger
bark insectivore vs. timber-foliage insectivore
low-understory herbivore/insectivore vs. nectarivore
timber-foliage insectivore vs. aerial insectivore
omnivore/scavenger vs. aerial insectivore
timber-foliage insectivore vs. timber-seed eater
omnivore/scavenger vs. timber-seed eater
bark insectivore vs. timber-seed eater
aerial insectivore vs. nectarivore
low-understory herbivore/insectivore vs. aerial insectivore
bark insectivore vs. low-understory herbivore/insectivore
low-understory herbivore/insectivore vs. omnivore/scavenger
low-understory herbivore/insectivore vs. timber-seed eater
timber-foliage insectivore vs. low-understory herbivore/insectivore
aerial insectivore vs. timber-seed eater
nectarivore vs. timber-seed eater
All Guilds
A
0.001
0.011
0.012
0.017
0.023
0.024
0.026
0.033
0.036
0.039
0.054
0.056
0.058
0.094
0.157
0.181
0.195
0.244
0.273
0.424
0.471
0.178
P
0.429
0.190
0.256
0.020
0.025
0.005
0.002
0.045
0.007
0.019
0.001
0.008
0.001
0.158
<0.001
<0.001
<0.001
<0.001
<0.001
0.004
0.017
<0.001
135
Appendix L: Multi-response permutation procedures pairwise comparisons of species by
epiphyte foraging activity, data pooled (N = 191). Bonferroni-adjusted significant P-values
indicating among group dissimilarity and within group similarity are highlighted in bold.
Groups
Brown Creeper vs. Golden-crowned Kinglet
Brown Creeper vs. Hairy Woodpecker
Brown Creeper vs. Hermit Thrush
Brown Creeper vs. Pacific-slope Flycatcher
Brown Creeper vs. Red Crossbill
Brown Creeper vs. Rufous Hummingbird
Brown Creeper vs. Steller's Jay
Chestnut-backed Chickadee vs. Brown Creeper
Chestnut-backed Chickadee vs. Dark-eyed Junco
Chestnut-backed Chickadee vs. Golden-crowned Kinglet
Chestnut-backed Chickadee vs. Gray Jay
Chestnut-backed Chickadee vs. Hairy Woodpecker
Chestnut-backed Chickadee vs. Hermit Thrush
Chestnut-backed Chickadee vs. Pacific-slope Flycatcher
Chestnut-backed Chickadee vs. Red Crossbill
Chestnut-backed Chickadee vs. Rufous Hummingbird
Chestnut-backed Chickadee vs. Steller's Jay
Chestnut-backed Chickadee vs. Winter Wren
Dark-eyed Junco vs. Brown Creeper
Dark-eyed Junco vs. Golden-crowned Kinglet
Dark-eyed Junco vs. Hairy Woodpecker
Dark-eyed Junco vs. Hermit Thrush
Dark-eyed Junco vs. Pacific-slope Flycatcher
Dark-eyed Junco vs. Red Crossbill
Dark-eyed Junco vs. Rufous Hummingbird
Dark-eyed Junco vs. Steller's Jay
Golden-crowned Kinglet vs. Hermit Thrush
Golden-crowned Kinglet vs. Red Crossbill
Gray Jay vs. Brown Creeper
Gray Jay vs. Dark-eyed Junco
Gray Jay vs. Golden-crowned Kinglet
Gray Jay vs. Hairy Woodpecker
Gray Jay vs. Hermit Thrush
Gray Jay vs. Pacific-slope Flycatcher
Gray Jay vs. Red Crossbill
Gray Jay vs. Rufous Hummingbird
Gray Jay vs. Steller's Jay
Hairy Woodpecker vs. Golden-crowned Kinglet
Hairy Woodpecker vs. Hermit Thrush
Hairy Woodpecker vs. Pacific-slope Flycatcher
A
0.025
0.044
0.113
0.066
0.212
0.612
0.074
0.101
0.009
0.006
0.018
0.037
0.118
0.037
0.055
0.013
0.005
0.311
0.026
0.642
0.454
0.092
0.035
0.279
0.011
0.535
0.207
0.425
0.088
0.667
0.001
0.017
0.087
0.039
0.062
0.012
0.540
0.037
0.155
0.021
P
0.121
0.006
<0.001
0.002
<0.001
<0.001
0.002
<0.001
0.181
0.312
0.024
0.004
<0.001
0.007
0.001
0.179
0.266
<0.001
0.081
<0.001
<0.001
0.099
0.257
0.007
0.445
<0.001
0.024
0.019
<0.001
<0.001
0.453
0.092
0.001
0.025
0.008
0.279
<0.001
0.200
0.004
0.200
136
Groups
Hairy Woodpecker vs. Red Crossbill
Hairy Woodpecker vs. Rufous Hummingbird
Hairy Woodpecker vs. Steller's Jay
Hermit Thrush vs. Red Crossbill
Pacific-slope Flycatcher vs. Golden-crowned Kinglet
Pacific-slope Flycatcher vs. Hermit Thrush
Pacific-slope Flycatcher vs. Red Crossbill
Pacific-slope Flycatcher vs. Rufous Hummingbird
Pacific-slope Flycatcher vs. Steller's Jay
Red-breasted Nuthatch vs. Brown Creeper
Red-breasted Nuthatch vs. Chestnut-backed Chickadee
Red-breasted Nuthatch vs. Dark-eyed Junco
Red-breasted Nuthatch vs. Golden-crowned Kinglet
Red-breasted Nuthatch vs. Gray Jay
Red-breasted Nuthatch vs. Hairy Woodpecker
Red-breasted Nuthatch vs. Hermit Thrush
Red-breasted Nuthatch vs. Pacific-slope Flycatcher
Red-breasted Nuthatch vs. Red Crossbill
Red-breasted Nuthatch vs. Rufous Hummingbird
Red-breasted Nuthatch vs. Steller's Jay
Red-breasted Nuthatch vs. Winter Wren
Rufous Hummingbird vs. Golden-crowned Kinglet
Rufous Hummingbird vs. Hermit Thrush
Rufous Hummingbird vs. Red Crossbill
Rufous Hummingbird vs. Steller's Jay
Steller's Jay vs. Golden-crowned Kinglet
Steller's Jay vs. Hermit Thrush
Steller's Jay vs. Red Crossbill
Winter Wren vs. Brown Creeper
Winter Wren vs. Dark-eyed Junco
Winter Wren vs. Golden-crowned Kinglet
Winter Wren vs. Gray Jay
Winter Wren vs. Hairy Woodpecker
Winter Wren vs. Hermit Thrush
Winter Wren vs. Pacific-slope Flycatcher
Winter Wren vs. Red Crossbill
Winter Wren vs. Rufous Hummingbird
Winter Wren vs. Steller's Jay
All Species
A
0.209
0.023
0.037
0.610
0.115
0.329
0.424
0.094
0.142
0.181
0.018
0.076
0.062
0.043
0.105
0.292
0.153
0.059
0.074
0.018
0.395
0.010
0.159
0.471
0.115
0.481
0.275
0.176
0.237
0.077
0.097
0.230
0.201
0.006
0.237
0.353
0.062
0.178
0.178
P
0.001
0.284
0.149
0.003
0.159
0.003
0.004
0.158
0.032
<0.001
0.037
0.027
0.069
0.010
0.002
<0.001
0.001
0.032
0.055
0.209
<0.001
<0.001
0.029
0.017
0.176
<0.001
0.010
0.023
<0.001
0.001
0.001
<0.001
<0.001
0.282
<0.001
<0.001
0.009
<0.001
<0.001
137
Appendix M: Number of species, guilds, and individuals (% of all substrates) that used epiphyte, phorophyte and other substrates by survey type.
Substrate
Other
Phorophyte
Epiphyte
Alectorioid lichen
Cyanolichen and other lichen
Foliose lichen
Fruticose lichen
Other lichen
Admixture (fruticose & foliose)
Subtotal
Bryophyte
Pendant bryophyte
Appressed bryophyte
Subtotal
Admixture (lichen & bryophyte)
Epiphyte Total
Foliage (live and dead foliage)
Bark
Dead wood (includes rootwads)
Cone
Other (flower)
Mistletoe brooms
Phorophyte Total
Air
Perched litter
Ground
Terrestrial herbs/mosses
Other
Other Total
All Substrates Total
Tree Plots
Walking Transects
No. species
No. guilds
No. inds
No. species
No. guilds
No. inds
4
4
10
7
5
16
6
2
2
5
6
5
1
2
4
5
30
2
3
13
48
8
1
7
4
10
4
1
4
3
5
18
2
11
5
36
2
3
3
--9 (50.0%)
12
11
6
1
1
2
15 (83.3%)
4
2
1
----7 (38.9%)
18
2
3
3
--6
7
7
5
1
1
2
7
6
2
1
----6
8
3
5
8
--66 (28.0%)
68
47
18
23
1
3
160 (67.8%)
7
2
1
----10 (4.2%)
236
10
8
12
3
14 (56.0%)
14
18
11
1
1
3
22 (88.0%)
6
1
5
4
2
10 (40.0%)
25
6
4
7
3
7
7
8
5
1
1
3
9
4
1
3
2
2
6
9
50
35
85
4
141 (28.3%)
115
121
56
7
7
5
311 (62.4%)
16
1
17
10
2
46 (9.2%)
498
Appendix N: Percent total foraging, postures, maneuvers, and mean foraging height (m) of 6 bird species searching epiphyte functional groups,
relative to all substrates, Tree Plots only.
Alectorioid
Lichens
Cyanolichens
and Other
Lichens
Bryophytes
Epiphyte
Foraging
Posture1
Epiphyte
Foraging
Maneuver2
Epiphyte
Foraging Height
(range)
Foraging Height
of Non-Epiphytes
(range)
0
20.0
10.0
HA
S
19.3 (12-32)
28.0 (22-41)
Chestnut backed Chickadee (63)
7.9
30.2
0
HA, HP, PE, SF,
LE/HG
S, GL, PR
31.9 (9-45)
28.4 (1-55)
Gray Jay (48)
6.3
14.6
8.3
PE, HA, RU,
HG
S, GL,
PK/PR,
PL/HA
26.9 (2.25-50)
33.6 (0-60)
Red-breasted Nuthatch (33)
3.0
33.3
0
HA, PE, HG,
HP
S, PR,
HA/PK
37.6 (24-60)
35.3 (24-60)
0
7.1
21.4
HP, PE/RP
S, GL/PK
0.9 (0.2-1.75)
0.6 (0-2)
2.9
8.6
0
PE
S, PK/PR
45.0 (40-50)
45.3 (30-60)
English Name
(n, total observations)
REGULAR USERS
Brown Creeper (10)
Winter Wren (14)
OCCASIONAL USERS/GENERALISTS
Red Crossbill (35)
1
2
postures: HA = hang, PE = perch, HG = hang upside-down, HP = hop, RU = reach under, LE = lean into, RP = reach up, SF = short flight (within substrate);
maneuvers: S = search, PR = probe, HA = hammer, PK = peck, GL = glean, PL = pluck; postures and maneuvers listed in order of importance.
Appendix O: Percent total foraging, postures, maneuvers and foraging height (m) of 12 bird species searching epiphyte functional groups,
relative to all foraging substrates, Walking Transects only.
Alectorioid
Lichens
Cyanolichens
and Other
Lichens
Bryophytes
Epiphyte
Foraging
Posture1
Epiphyte
Foraging
Maneuver2
Epiphyte
Foraging Height
(mean, range)
Foraging Height of
Non-Epiphytes
(mean, range)
9.8
19.5
29.3
HA, HG/PE
S/PK, PR, GL,
PL
10.7 (1-23)
11.6 (1-25)
0
5.3
23.7
HA, PE, HG
HA, PK, S
12.4 (1-40)
19.3 (2-60)
8.3
11.7
16.7
PE, HA, LE,
HG/RU
S, PK, GL, PR
18.0 (2-50)
18.4 (0-58)
Winter Wren (85)
0
3.5
35.3
HP/PE, HA/SD,
LE/RP, AM, HO
PK, S, GL, PR
1.5 (0-8)
0.9 (0-10)
Hermit Thrush (17)
0
5.9
23.5
PE, LE, AM
S, PK
1.3 (0-2)
1.5 (0-5.5)
Red-breasted Nuthatch (27)
3.7
11.1
7.4
HA, PE
PK/S
27.5 (3-60)
32.8 (11-58)
Chestnut backed Chickadee
(104)
2.9
1.9
6.7
HA, HG, PE,
HP/LE/HO, SF
S, GL, PK, PR,
PL
14.5 (1.5-55)
16 (1.5-55)
0
11.1
0
PE
S
12.0 (6-18)
16.3 (6-35)
4.5
4.5
9.1
LE/PE/RU/SD
PK, GL/S
11.2 (0.75-23)
1.3 (0-5)
Pacific-slope Flycatcher (43)
0
2.3
7.0
HO
GL
15.8 (6-27)
14 (0-40)
Red Crossbill (8)
0
0
0
---
---
---
36.9 (27-45)
7.1
0
7.1
HO
S
11.8 (5.5-18)
5.6 (0.5-40)
English Name
(n, total observations)
REGULAR USERS
Brown Creeper (41)
Hairy Woodpecker (38)
Gray Jay (60)
OCCASIONAL USERS/GENERALISTS
Golden crowned Kinglet (18)
Dark-eyed Junco (22)
Rufous Hummingbird (14)
1
Postures: HA = hang, PE = perch, HG = hang upside-down, HP = hop, RU = reach under, LE = lean into, RP = reach up, SF = short flight (within substrate), SD = stand, AM =
walk/run on ground, HO = hover; 2Maneuvers: S = search, PR = probe, HA = hammer, PK = peck, GL = glean, PL = pluck; postures and maneuvers listed in order of importance.
Appendix P: Multi-response permutation procedures pairwise comparisons of finer scale
epiphyte substrates used by all birds observed in the Tree Plots and Walking Transects.
Significant P-values indicating among group dissimilarity and within group similarity are
highlighted in bold.
Tree Plots
Walking Transects
A value
P - value
A value
P - value
0.201
< 0.001
AB vs. AL
0.222
0.001
0.055
0.004
AB vs. MIX
----0.069
< 0.001
AB vs. OL
-0.023
0.587
0.062
< 0.001
AB vs. PB
-0.019
0.498
AL vs. MIX
----0.066
0.043
0.032
0.081
AL vs. OL
0.135
0.025
AL vs. PB
0.391
0.003
0.106
< 0.001
0.150
< 0.001
0.099
0.014
FF vs. AB
-0.00001
0.379
FF vs. AL
0.050
0.034
-0.004
0.421
FF vs. FR
-0.001
0.422
0.216
0.005
----FF vs. MIX
FF vs. OL
0.021
0.259
0.090
0.031
0.077
< 0.001
FF vs. PB
0.150
0.017
0.147
< 0.001
FO vs. AB
0.088
< 0.001
0.038
0.028
FO vs. AL
0.040
0.006
0.060
0.019
FO vs. FF
-0.010
0.864
0.019
0.195
FO vs. FR
0.001
0.422
-0.0003
0.439
FO vs. MIX
----0.032
0.047
FO vs. OL
0.026
0.061
0.044
< 0.001
FO vs. PB
0.089
0.004
0.084
< 0.001
FR vs. AB
-0.005
0.489
FR vs. AL
0.090
0.022
0.014
0.283
0.161
0.035
FR vs. MIX
----0.066
0.086
FR vs. OL
-0.056
--0.039
0.004
FR vs. PB
0.117
--OL vs. MIX
----0.011
0.313
OL vs. PB
0.092
--0.024
0.016
PB vs. MIX
----0.003
0.546
All epiphytes
0.111
< 0.001
0.151
< 0.001
1
AL = alectorioid lichen, FO = foliose lichen, FR = fruticose lichen, FF = fruticose and foliose
lichen, PB = pendant bryophyte, AB = appressed bryophyte, OL = other lichen, MIX = bryophyte
and lichen
Groups1
141
Appendix Q: Multi-Response Permutation Procedures pairwise comparisons of foraging guilds
by finer scale epiphyte substrate foraging activity in the Tree Plots and Walking Transects.
Significant P-values indicating among group dissimilarity and within group similarity are
highlighted in bold.
Tree Plots
Walking Transects
A value
P - value
A value
P - value
0.043
0.005
AI vs. BI
----0.111
< 0.001
AI vs. LUHI
----0.198
0.054
AI vs. N
----0.077
0.007
AI vs. OS
----0.046
0.013
AI vs. TFI
----0.134
<
0.001
BI vs. LUHI
0.293
< 0.001
-0.001
0.468
BI vs. N
----0.033
0.004
BI vs. OS
0.025
0.066
0.017
0.024
BI vs. TFI
0.004
0.298
BI vs. TS
0.093
0.006
----0.029
0.036
N vs. LUHI
----0.124
< 0.001
OS vs. LUHI
0.180
0.001
0.013
0.286
OS vs. N
----OS vs. TS
0.077
0.020
----0.162
< 0.001
TFI vs. LUHI
0.263
< 0.001
0.007
0.316
TFI vs. N
----0.015
0.080
TFI vs. OS
0.036
0.011
TFI vs. TS
0.089
0.002
----TS vs. LUHI
0.579
0.009
----0.144
< 0.001
All Guilds
0.159
< 0.001
1
AI = aerial insectivores, BI = bark insectivores, LUHI = low understory herbivores/insectivores,
N = nectarivores, OS = omnivore/scavenger, TFI = timber-foliage insectivores, TS = timber-seed
eaters
Groups1
142
Appendix R: Mean number of birds detected in 30 m- and unlimited-radius VCP by observer
location (flyovers, juveniles, and flushed birds included).
English Name
Red Crossbill
Winter Wren
Pacific-slope Flycatcher
Red-breasted Nuthatch
Vaux’s Swift
Chestnut-backed Chickadee
Hermit Thrush
Brown Creeper
Hermit Warbler
Steller’s Jay
Gray Jay
Golden-crowned Kinglet
Tree Swallow
Pine Siskin
Common Raven
American Robin
Dark-eyed Junco
Rufous Hummingbird
Western Tanager
Hammond's Flycatcher
Barred Owl
Black-headed Grosbeak
Evening Grosbeak
Hairy Woodpecker
Northern Flicker
Olive-sided Flycatcher
Purple Finch
Red-breasted Sapsucker
Ruby-crowned Kinglet
Swainson’s Thrush
Western Wood-Pewee
Yellow-rumped Warbler
American Goldfinch
Common Nighthawk
Pileated Woodpecker
Song Sparrow
No. of individuals/plot
No. of species/plot
Unlimited-Radius
Canopy
Ground
2.8 ± 1.73
2.4 ± 1.13
1.75 ± 0.22
1.35 ± 0.18
1.35 ± 0.25
0.95 ± 0.2
1.3 ± 0.18
0.75 ± 0.12
1.25 ± 0.35
0.5 ± 0.21
1.25 ± 0.26
0.85 ± 0.25
0.75 ± 0.22
0.6 ± 0.23
0.65 ± 0.15
0.5 ± 0.15
0.55 ± 0.21
0.15 ± 0.08
0.55 ± 0.21
0.4 ± 0.13
0.5 ± 0.14
0.35 ± 0.13
0.35 ± 0.13
0.25 ± 0.16
0.25 ± 0.1
0.05 ± 0.05
0.2 ± 0.14
0.05 ± 0.05
0.2 ± 0.09
0±0
0.15 ± 0.08
0.1 ± 0.07
0.15 ± 0.08
0.1 ± 0.07
0.15 ± 0.08
0.15 ± 0.08
0.15 ± 0.08
0±0
0.1 ± 0.1
0.05 ± 0.05
0.05 ± 0.05
0.05 ± 0.05
0.05 ± 0.05
0.05 ± 0.05
0.05 ± 0.05
0.15 ± 0.08
0.05 ± 0.05
0.1 ± 0.07
0.05 ± 0.05
0.05 ± 0.05
0.05 ± 0.05
0±0
0.05 ± 0.05
0±0
0.05 ± 0.05
0.05 ± 0.05
0.05 ± 0.05
0.05 ± 0.05
0.05 ± 0.05
0.05 ± 0.05
0.05 ± 0.05
0±0
0.05 ± 0.05
0.05 ± 0.05
0±0
0.05 ± 0.05
0±0
0.05 ± 0.05
0±0
0.05 ± 0.05
0±0
0.05 ± 0.05
15.05 ± 1.86
10.4 ± 1.34
8.45 ± 0.55
6.4 ± 0.56
30 m-Radius
Canopy
Ground
2.7 ± 1.73
2.35 ± 1.13
0.7 ± 0.18
0.65 ± 0.21
0.3 ± 0.15
0.2 ± 0.12
0.15 ± 0.08
0.15 ± 0.08
1.25 ± 0.35
0.5 ± 0.21
0.7 ± 0.28
0.75 ± 0.25
0.05 ± 0.05
0.15 ± 0.08
0.15 ± 0.08
0.25 ± 0.12
0.15 ± 0.11
0.05 ± 0.05
0.05 ± 0.05
0±0
0±0
0.1 ± 0.07
0.1 ± 0.07
0.25 ± 0.16
0.25 ± 0.1
0.05 ± 0.05
0±0
0.05 ± 0.05
0±0
0±0
0±0
0±0
0.05 ± 0.05
0.05 ± 0.05
0.15 ± 0.08
0.15 ± 0.08
0±0
0±0
0±0
0±0
0±0
0±0
0.05 ± 0.05
0±0
0.05 ± 0.05
0.05 ± 0.05
0±0
0±0
0±0
0±0
0±0
0±0
0±0
0±0
0±0
0±0
0.05 ± 0.05
0.05 ± 0.05
0.05 ± 0.05
0.05 ± 0.05
0±0
0±0
0±0
0.05 ± 0.05
0±0
0.05 ± 0.05
0±0
0.05 ± 0.05
0±0
0±0
0±0
0±0
6.95 ± 1.72
6.0 ± 1.07
3.25 ± 0.28
3.0 ± 0.32
143
Appendix S: Frequency of occurrence of all bird species by observer location (flyovers,
juveniles, and flushed birds included).
English Name
Winter Wren
Red-breasted Nuthatch
Pacific-slope Flycatcher
Chestnut-backed Chickadee.
Vaux’s Swift
Brown Creeper
Hermit Thrush
Purple Finch
Swainson’s Thrush
Evening Grosbeak
Northern Flicker
Olive-sided Flycatcher
Western Wood-Pewee
Yellow-rumped Warbler
Hammond's Flycatcher
Black-headed Grosbeak
Hairy Woodpecker
Ruby-crowned Kinglet
Red-breasted Sapsucker
Barred Owl
Gray Jay
Steller’s Jay
Red Crossbill
Hermit Warbler
Golden-crowned Kinglet
Tree Swallow
Common Raven
Dark-eyed Junco
Western Tanager
Rufous Hummingbird
American Robin
Pine Siskin
American Goldfinch
Common Nighthawk
Pileated Woodpecker
Song Sparrow
Unlimited Radius
Canopy
Ground
90
85
85
70
75
65
65
50
60
25
55
40
50
35
5
0
5
5
5
15
5
5
5
0
5
0
5
5
5
5
5
5
5
10
5
5
5
5
5
5
45
30
40
35
35
40
30
15
30
15
25
5
20
0
15
10
15
0
15
15
15
10
10
5
0
5
0
5
0
5
0
5
30 m Radius
Canopy
Ground
55
40
15
15
20
15
30
40
60
25
15
20
5
15
0
0
5
5
5
5
0
0
0
0
0
0
0
5
0
0
5
0
0
0
5
5
0
0
0
0
0
10
5
0
35
40
10
5
10
15
25
5
0
0
5
5
0
0
15
15
0
0
0
5
0
5
0
5
0
0
0
0
144
Appendix T: Histogram of A) canopy-level and B) ground-level observer detection distances
(m) for nine core species (BRCR = Brown Creeper, CBCH = Chestnut-backed Chickadee, GCKI
= Golden-crowned Kinglet, GRAJ = Gray Jay, HETH = Hermit Thrush, HEWA = Hermit
Warbler, PSFL = Pacific-slope Flycatcher, RBNU = Red-breasted Nuthatch and WIWR = Winter
Wren).
35
A
BRCR
CBCH
GCKI
GRAJ
HETH
HEWA
PSFL
RBNU
WIWR
Number of birds (frequency)
30
25
20
15
10
5
0
10
20
30
40
50
60
70
80
90
100
More
Detection Distance (m)
35
B
Number of birds (frequency)
30
25
BRCR
CBCH
GCKI
GRAJ
HETH
HEWA
PSFL
RBNU
WIWR
20
15
10
5
0
10
20
30
40
50
60
70
80
90
100
More
Detection Distance (m)
145
Insert Colored Paper
146
Wolf_ALMESThesis2009.pdf