AN ABSTRACT OF THE THESIS OF
Tiffany A. Brett for the degree of Master of Science in Wildlife Science presented on
July 21, 1997. Title: Habitat Associations of Woodpeckers in Managed Forests of
the Southern Oregon Cascades.
Abstract approved:
John P. HaY(s
Abstract approved:
William C. McComb
I studied nest-site characteristics and habitat relationships for three species of
primary cavity-nesting birds--hairy woodpecker (Picoides villosus), northern flicker
(Colaptes auratus), and red-breasted sapsucker (Sphyrapicus ruber)-- over spatially
heterogeneous landscapes in managed forests of the Southern Oregon Cascades during
1995 and 1996. The study was conducted on the Diamond Lake Ranger District of the
Umpqua National Forest. I found 163 nests--68 nests of red-breasted sapsuckers, 63 of
northern flickers, and 32 of hairy woodpeckers. I evaluated characteristics of nest trees,
habitat within a 0.04-ha circle surrounding nest trees, and the surrounding landscape and
compared these to characteristics of randomly selected plots. Analysis revealed
statistically significant differences between nest trees and random trees among species.
Variables significantly influencing the probability of use of a tree were state of decay,
diameter at breast height, and tree top condition (broken or intact). Red-breasted
sapsucker nests were associated with large diameter (mean
tops. Hairy woodpeckers used large diameter (mean
80.5 cm) trees with broken
80.4 cm) trees in decay class 3 for
nesting. Northern flickers were associated with large diameter trees (mean = 77.7 cm)
with broken tops. I investigated habitat associations at the landscape level using GIS
coverages and FRAGSTATS spatial analysis to generate indices quantifying landscape
structure for each study site. Higher numbers of woodpecker nests were found in
landscapes with lower proportions of mature closed-canopy forest (trees> 53 cm, canopy
closure > 40%), and possessing greater overall habitat complexity. I also detected a
significant association between all three species of woodpecker and proximity to edge.
Red-breasted sapsuckers exhibited the most dramatic affinity for edge habitat, choosing
to use nest trees located on a habitat edge more often than would be expected if selection
was due to chance alone (P < 5 x 1(f9). Nests of northern flickers and hairy woodpeckers
were also significantly associated with habitat edges (P <0.004 and P <0.04
respectively). When managing for woodpeckers within managed forest landscapes, large
snags (>80 cm) should be retained. Woodpecker needs for nesting habitat may not be
met if retained snags do not represent a diversity of decay classes. Snags representing a
variety of tree species and decay classes should be left following management activity.
Additionally, management plans should incorporate the use of a variety of methods for
stand regeneration. Using prescriptions such as shelterwoods, commercial thinning, and
partial cuts, overall landscape diversity will increase, enhancing habitat conditions for
nesting woodpeckers.
Habitat Associations of Woodpeckers at Multiple Scales in Managed Forests of the
Southern Oregon Cascades
by
Tiffany A. Brett
A THESIS
submitted to
Oregon State University
in partial fulfillment of
the requirements for the
degree of
Master of Science
Presented July 21, 1997
Commencement June, 1998
Master of Science thesis of Tiffany A. Brett presented on July 21, 1997
APPROVED:
Co-Major
representing Wildlife Science
I understand that my thesis will become part of the permanent collection of Oregon
State University libraries. My signature below authorizes release of my thesis to any
reader upon
Tiffany A. Brett, Author
-Acknowledgements
My thesis work was funded by DEMO (Demonstration of Ecosystem
Management Options), a cooperative research project initiated in Oregon and
Washington in 1994. I am grateful to the organizers of the project, and most especially
the technical support from the Diamond Lake Ranger District.
This thesis was inspired and encouraged by many, I could not possibly mention
them all here. To my major advisors Bill McComb and John Hayes, I offer my sincere
thanks in allowing me to 'explore' while keeping me on track with their timely
encouragement and advice. I am especially grateful to John for his patient guidance
throughout the analysis and writing of the thesis, his thoughtful advice and support were
invaluable. I would like to thank the other members of my committee as well; Dan Edge
for his tireless cheer, and Susan Stafford, not only for her statistical advice, but also for
her encouraging words.
I thank Sandy Lewis for her tireless attention to bureaucratic details, and her
constant smile. I am grateful to Logan Norris, department head and supporter, for his
unending optimism with regards to the DEMO project. I would be remiss without
thanking Carol Chambers, who had enough faith in me to choose me as a research
assistant on the DEMO project in 1994. Carol was always there to offer professional and
personal advice whenever it was needed. Gody Spycher, database whiz and fellow lover
of Rilke, was always willing to share bits of wisdom on database management, and would
help out with SAS problems in a pinch. His cheery disposition got me through some of
the rough spots in the analysis. I would have been lost had it not been for the GIS
wizardry of George Leinkaemper. He patiently guided me through the painful
introductory stages of Arc Info, and in the process turned me on to the wonders of spatial
analysis with his always-present enthusiasm. Thanks also to Barbara Marks, who aided
in analysis with FRAGSTATS. My work would not have been possible without the
assistance of these two people.
I am grateful for the support of my friends and colleagues, I would not have made
it through this difficult time without their empathy and understanding. Special thanks to
friends and fellow classmates Jennifer Weikel, Nobi Suzuki, and Jonathon Brooks, who
gave invaluable advice along the way. Thanks to Matthew Hunter not only for his
endless enthusiasm for all creatures winged and otherwise, but also for his thoughtful
comments which inspired ideas during the later writing stages. To fellow Wisconsinite
Joan Hagar I am grateful, as someone with whom I could share my love for birds, and
who was always willing to 'lend an ear' when I needed one. I am indebted to Louise
Yount and Shelley Church, who were always there for me when the going got tough, and
who have become very dear friends along the way. I would like to acknowledge and
thank fellow Demo researchers Rebecca Thompson, and Jeff Feen, with whom I shared
the joys and frustrations of field work. Jeff, despite being a 'mammal guy' has become a
dear friend during the last two years (even though he remains a staunch advocate of Fords
and flying squirrels).
I would like to thank those who have worked hard to help me collect the data
during the past two years; including Wayne Harris, Sue Danver, and the Swift sisters
Roberta and Stephanie. Thanks to Lyndia Hammer for her endless enthusiasm and to
Anthony Floyd for his loyalty and hard work. I owe a great deal to Anthony, who not
only shared my love of feathered critters, but also stuck out two field seasons, putting up
with the hard work and delightful spring weather of the Oregon Cascades-cheerfully for
the most part.
I owe gratitude to many forest service employees at the Diamond Lake Ranger
District who generously provided technical support throughout the duration of my study.
To Rick Abbott, die-hard supporter of DEMO, I thank for accommodating all DEMO
researchers, and dealing with problems we encountered along the way. I am grateful to
Kim Vieira, GIS guru on the district, for her patient direction in my explorations of GIS
and Arc-Info. I am grateful to friends and a fellow bird-enthusiasts Keith and Mary
Graves. Keith, as district recreation specialist/biologist, gave freely of his advice and
support throughout the study.
I am most grateful to my parents Frank and Chris Church, who encouraged me in
all of my explorations. Thanks to my father, for cultivating in me a love and respect for
nature as a young girl, and for sharing his awe and wonder in things natural, wild, and
free. He is responsible for 'planting the seed' that blossomed into my passion (some
might call it obsession) for birds. I will always be grateful to my mother for helping me
to see beauty in all things, and for her tireless support and undying faith in me.
Finally, I would like to thank my husband Joe, who besides being wonderfully
supportive throughout, also gave freely of his time to instruct me in the use of the GPS
satellite equipment, and helped me to create the map coverages I needed for analysis. I
especially thank Joe for his constant love and patience, and for sharing his love and
knowledge of the Diamond Lake area with me.
TABLE OF CONTENTS
Page
CHAPTER 1- HABITAT ASSOCIATIONS OF WOODPECKERS
AT MULTIPLE SCALES IN MANAGED FORESTS
OF TIlE SOUTHERN OREGON CASCADES
CONCEPTUAL BACKGROUND
1
RESEARCH NEED AND JUSTIFICATION
5
Management
Woodpeckers of the Southern Oregon Cascades
Snag
7
7
OBJECTiVES
8
LITERATURE CITED
9
CHAPTER 2- NEST-SITE CHARACTERISTICS OF WOODPECKERS
IN MANAGED FORESTS OF THE SOUTHERN OREGON
CASCADES
13
INTRODUCTION
13
STUDY AREA
15
METHODS
19
Study-Site Selection
Bird Sampling and Nest Searches
Habitat Sampling
Data Analysis
RESULTS
Characteristics of Nest Trees
Multivariate analysis
DISCUSSION
Diameter
Tree Condition and Decay
Tree Species
19
19
20
22
23
24
26
32
32
34
34
CONCLUSION
35
LITERATURE CITED
36
TABLE OF CONTENTS (continued)
Page
CHAPTER 3- HABITAT ASSOCIATIONS OF WOODPECKERS
AT TILE LANDSCAPE LEVEL IN MANAGED FORESTS
OF THE SOUTHERN OREGON CASCADES
41
INTRODUCTION
41
OBJECTIVES
42
STUDY AREA
43
METHODS
46
Study Site Selection
Bird Sampling and Nest Searches
Creating a GIS Layer
Statistical analysis
RESIJLTS
FRAGSTATS analysis of Landscape Indices
Edge Analysis
DISCUSSION
Species-Specific Patterns
Edge Effect
46
47
48
48
52
52
56
58
58
60
CONCLUSION
61
L1TERATEJRE CITED
62
CHAPTER 4- CONCLUSIONS AND IMPLICATIONS FOR
MANAGEMENT FOR WOODPECKERS IN TILE OREGON
CASCADES
66
LARGE DIAMETER SNAGS
EDGE
NATURAL AGENTS OF DIVERSITY
RESEARCH RECOMMENDATIONS
66
67
68
69
LiTERATURE CITED
70
TABLE OF CONTENTS(continued)
Page
BIBLIOGRAPhY
73
APPENDICES
81
Appendix A Maps of eleven study sites showing habitat patch
type and spatial arrangement, and location of
woodpecker nests at each site
82
Appendix B.
Appendix C
Weight file used in FRAGSTATS analysis to
characterize vegetation characteristics of 200-ha
landscapes where woodpecker nests were located
on the Diamond Lake Ranger District
Class level indices generated in FRAGSTATS to
characterize eleven 200-ha landscapes on the
Diamond Lake Ranger District, Umpqua National
Forest, southern Oregon Cascades, 1995-1996
94
95
LIST OF FIGURES
Page
Fi2ure
Location of study sites for woodpecker habitat
association study on the Diamond Lake Ranger District
Umpqua National Forest, Southern Oregon Cascades
17
2.
Diameter of woodpecker nest trees and random trees.
25
3.
Tree-top condition for trees used for nesting by hairy
woodpeckers (HAWO), red-breasted sapsuckers (RBSA),
and northern flickers (NOFL) and for random trees.
25
Decay class for nest trees of hairy woodpeckers (HAWO),
red-breasted sapsuckers (RBSA), northern flickers (NOFL)
and random trees.
28
1.
4.
5.
6.
7.
8.
9.
Tree species groups of nest trees for hairy woodpeckers
(HAWO), red-breasted sapsuckers (RBSA),
northern flickers (NOFL) and random trees.
28
Location of study sites for woodpecker habitat
association study on the Diamond Lake Ranger District
Umpqua National Forest, Southern Oregon Cascades.
45
Association between the log of mean forest patch size
and density of red-breasted sapsucker nests over landscapes.
53
Association between proportion of mature forest and density
of northern flicker nests over landscapes.
54
Association between proportion of mature forest and density
of hairy woodpecker nests Over landscapes.
55
LIST OF TABLES
Pa2e
Table
1.
2.
3.
4.
5.
6.
7.
8.
9.
I 0.
Definition of habitat characteristics measured in plots
centered around woodpecker nest trees and random trees.
21
Number of nests of woodpeckers found during 1995-96
breeding seasons in 11 study-sites located in the Southern
Oregon Cascades.
24
Mean values nest tree characteristics for hairy woodpeckers,
northern flickers and red-breasted sapsuckers.
27
Results of multiple logistic regression comparing tree
characteristics for nests of red-breasted sapsuckers
compared to random trees.
29
Results of multiple logistic regression comparing tree
characteristics nests of hairy woodpeckers compared to
random trees.
30
Results of multiple logistic regression comparing tree
characteristics nests of northern flickers compared
to random trees.
31
Patch type classification system used for FRAGSTATS
analysis to classify vegetation in 200-ha study sites.
49
Definitions of class level habitat variables generated by
FRAGSTATS to describe landscape characteristics in
200-ha sites.
51
Location of nests of red-breasted sapsuckers, hairy
woodpeckers and northern flickers with respect to edge
within landscapes.
56
Comparison of distance from an edge between woodpecker
nests and random locations, after all points located directly
on an edge were removed
57
PREFACE
Timber harvest in the Cascade region of the Pacific Northwest dates back to 1827
with the construction of the first water-driven sawmill in the region (Hams 1984). The
Pacific Northwest region is known for its ability to produce timber, and is marveled for
expansive conifer-dominated forests and trees of massive proportions. Timber harvest
during the last 50 years has created landscapes comprised of patchwork configurations of
older forest interspersed with younger seral-stage stands (Franidin and Forman 1987).
The forest fragments created acquire characteristics of habitat islands in proportion to
their size and length of time since isolation (Harris 1984). This practice has led to a
severe reduction in the amount of low elevation old-growth forest, with the total acreage
amounting to 10% of its original volume. In addition, the continuous nature of the forest
prior to logging has been altered.
Large-scale changes in landscape pattern have occurred within the last century,
yet we have limited understanding of the consequences of altered landscape pattern on
wildlife species and ecosystems. We need to reexamine whether traditional silvicultural
methods of timber harvest are compatible with emerging concerns of biodiversity
protection and overall forest ecosystem integrity.
In the past, scientists have approached problems through studies that examine
organisms or processes using the reductionist philosophy rooted in mechanistic science.
Mechanistic theory was developed and used with great success by pioneers such as
Francis Bacon, René Descartes, and Isaac Newton. It is based upon the premise that any
system or process can be understood by dissecting it to its smallest components.
Investigation of the individual pieces, according to the theory, will lead to an
understanding of the whole (Capra 1982). One of the major disadvantages of using the
reductive, mechanistic approach is its severe limitations when applied to complex biotic
systems. In many cases, study designs are oblivious to the importance of scale in
examining wildlife habitat associations. The manner in which we make observations
directly influences the conclusions we can draw from our observations, complete
disregard for the effects of scale can lead to false or incomplete conclusions. Realizing
the importance of scale, many researchers have begun exploring other methods of
research design to study wildlife populations.
I developed my research questions based on a perceived need to modify our
perspectives in research, to move beyond stand and organism-level studies towards
studies that examine dynamic systems and their related interactions. Forests have
become more intensively managed to meet a number of demands including timber
production, recreation, and maintenance of habitat for wildlife species. Forest managers
need information to help direct them in development and implementation of management
plans to satisfy these demands and maintain functioning forest systems. Because
management strategies are addressing problems that occur at the landscape level, it is
appropriate and necessary that we attempt to examine processes at this scale.
My thesis is arranged into three chapters; in Chapter One, I present the contextual
framework and justification for my research, to provide relevant information to help the
reader interpret the results in a meaningful way. To understand and appreciate the
problem, one must have an idea of the multiple dimensions in which it exists. In Chapter
Two, I present and discuss the results of the study at the smallest scale of resolution,
habitat associations of woodpeckers at the nest tree level. In Chapter Three, I describe
and discuss the results of the landscape level analyses, which considered habitat
associations of woodpeckers on a broader scale, examining relationships between nesting
woodpeckers and characteristics at the patch and landscape dimensions. I conclude with
a brief chapter integrating the results of both the nest tree level and landscape level
analyses, and present management recommendations based upon my findings.
McGarigal (1993) asserted: "there has been a great deal of theoretical and
conceptual work on populations or spatially complex environments, but few empirical
studies to confirm or refute these ideas." My goal in undertaking this research project is
to ask the bigger question, to look beyond current perspectives and attempt to examine
wildlife habitat interactions at multiple scales. I do not intend to produce a universal
solution to questions regarding habitat management for maintenance of viable
woodpecker populations. Rather, I wish to approach that question from a different angle,
and perhaps shed light on how to frame appropriate questions and design research
projects that examine wildlife-habitat relationships in a contextual way.
LITERATURE CITED
Capra, F. 1982. The turning point: science, society and the rising culture.
Bantam. New York, N.Y. 464 pp.
Franklin, J.F., and R.T. Forman. 1987. Creating landscape patterns by forest
cutting: ecological consequences and principles. Landscape Ecology 1: 5-18
Harris, L.D. 1984. The fragmented forest. University of Chicago Press, Chicago,
I.L. 2llpp.
McGarigal, K. 1993. Relationship between landscape structure and avian abundance
patterns in the Oregon Coast Range. Ph.D. Dissertation. Oregon State
University, Corvallis. 273 pp.
Habitat Associations of Woodpeckers at Multiple Scales in Managed Forests of the
Southern Oregon Cascades
CHAPTER 1
Introduction
CONCEPTUAL BACKGROUND
The Cascades region of the Pacific Northwest represents a bioregion with a great
diversity of habitats supporting a rich vertebrate community. The forests of the Pacific
Northwest are home to 251 species of breeding birds, 125 species of mammals, 26 species
of amphibians, and 28 species of reptiles (Harris 1984).
In recent decades, there has been increasing concern over the way in which our
public lands have been managed, specifically questioning whether management activities
are compatible with the conservation of unique flora and fauna. Alterations in landscape
structure due to timber harvest have had negative effects on some wildlife populations and
alarming declines in populations of many avian species have been documented. The
marbled murrelet (Brachyramphus marmoratus), a sea-bird that nests in old-growth trees,
was listed as threatened in 1994. The northern spotted owl (Sirix occidentalis caurina),
another old-growth associate, was added to the list of threatened species in 1991. The
decision to list the owl has had a profound effect, throwing the field of natural resource
management into a quagmire in an attempt to resolve conflicts between resource
extraction-based industry and wildlife management of threatened species. These issues
continue to challenge scientists and land managers, who are grappling with the complex
problem of managing natural resources to meet public demands while protecting habitat
for indigenous species.
Public involvement in forest management issues has increased, and with it has
come pressure to change forest management policy and practices. Demands on federal
forest lands have steadily increased, both in the form of recreational pressure and
2
demand for timber. Timber harvest is the dominant land management activity in the
federal forests of the Pacific Northwest (Edgerton and Thomas 1977). For the past 40
years, harvest has been conducted using even-aged management strategies. This method
has been followed primarily for economic and silvicultural reasons, because it allows for
relatively easy forest regeneration, slash disposal and road building. The resulting
landscape is characterized by patchwork configurations of mature forest interspersed with
even-aged regenerating stands (Franidin and Forman 1987). The openings created by
timber harvest disrupt the continuity of the forest and leave behind a patchwork mosaic,
reducing connectivity between forest patches (Harris 1984). With the recent shift to create
management strategies addressing ecosystem-level processes, we need to consider the
ecological consequences of forest fragmentation (Harris 1984). It is imperative that we
utilize silvicultural methods that retain overall ecosystem integrity, and preserve the
inherent biodiversity of forest ecosystems.
The foundation for understanding ecological processes on a broad scale is built
upon the evolving field of landscape ecology. This branch of ecology is a relatively new
scientific field. It focuses on the ecological structure, function and change of a landscape
(Forman and Godron 1981, Naveh and Lieberman 1984, Forman and Godron, 1986).
Detecting relationships at a landscape level poses a challenge for scientists, and requires a
major change in perception from traditional plot-level analyses. Wiens (1976) asserted
that ecologists have been slow in recognizing this need because humans are more likely
to perceive and study such phenomena on anthropocentric scales that are in accordance
with their own experience. In designing studies, we frequently select scales that appear to
be appropriate to observe phenomena, though that scale may be completely irrelevant to
the organism being studied. Often in field studies, observations are conducted over short
time periods and on small spatial scales, as a matter of convenience, despite the fact that
this can result in a skewed interpretation of organism response. As Wiens (1976) states,
"we need nonarbitrary operational ways of defining and detecting scales." Though a
noble objective, it is difficult to determine how to implement this in study design.
The crucial step in the design stage of a study is to define habitat patch from the
perspective of the organism. Environments can be patchy over landscapes, creating
3
patterns of heterogeneity that in turn influence vertebrate population abundance and
distribution (McGarigal 1993). The term patch must be defined within the context of the
question(s) of interest and the organism(s) being studied. Many definitions of patch are
found within the ecological literature. A resource patch is defined as "a nonlinear
surface area differing in appearance from its surroundings" (Forman and Godron 1986).
Wiens (1976) defined a patch as:
"relatively discrete areas of spatial or temporal domain of relatively
homogeneous environmental conditions where patch boundaries
are distinguished by discontinuities in environmental character
from their surroundings of magnitudes that are perceived by the
animal under consideration"
Patches are dynamic and inherently possess unique qualities such as vegetation
association, size, shape, interior-to-edge ratio, and boundary characteristics. Patches
exhibit an internal structure, referred to as patch hierarchy, in which heterogeneity occurs
at successively finer scales. In any study of wildlife-habitat associations, patch dynamics
must be considered because they influence species diversity and abundance.
Our ability to detect patterns within a patch are a function of both extent and
grain. Extent is the coarsest scale of heterogeneity to which an organism responds, and is
determined by the home range of the organism (Kotliar and Wiens 1990). For practical
purposes extent is usually restricted to the area encompassed by the study. Grain
represents the individual units of heterogeneity within a patch to which a species
responds (Wiens 1989). Within the context of a research study, these terms must be
defined as the upper and lower limits of resolution of a study.
Grain response may be either fine or coarse, and should be defined from an
organism-centered perspective. Grain size is determined by an organism's perceptual
abilities. A fine-grained response occurs when an organism does not perceive any
heterogeneity within the landscape beyond a sufficiently fine scale of resolution, i.e.
'grains' are used in direct proportion to their availability in the environment. Conversely,
a coarse-grained response is that level of patchiness at which patterns of use by an
4
organism are observed, in other words, 'grains' are used disproportionate to their
availability. Using the analogy of a foraging woodpecker to illustrate this concept,
consider that the home range of the woodpecker is 12-hectares. Within the 12-ha patch,
the woodpecker may perceive the entire area as homogeneous with respect to stand
structure, no behavioral response to stand structure is observed. The woodpecker could
be said to exhibit a fine-grained response with regard to stand structure at that particular
scale. If small groups of snags are found within the 12-ha patch that contain high
densities of insects that are desired food items, the woodpecker may select these trees for
foraging disproportionate to availability. This behavior illustrates a coarse-grained
response to snag distribution throughout the stand.
Patches are critical in determining the relative stability of a population in a
landscape. den Boer (1981) hypothesized that a population will be more persistent, and
therefore less at risk of extinction, in a landscape characterized by heterogeneity versus
one of a similar population occupying a homogeneous environment. Populations within a
heterogeneous landscape are hypothesized to be less susceptible to natural catastrophes
because even if populations in local patches go extinct, individuals from other patches
remain to recolonize the vacant patches (den Boer 1981). Van Home (1983) asserted
that patches with superior habitat function as 'source' patches. Source patches are crucial
because they are thought to provide dispersers to the overall population, enhancing
genetic diversity and providing stability to the population. Patches with inferior habitat
may be 'sinks', or patches where organisms can exist, but do not persist over time due to
decreased reproduction (Van Home 1983).
An understanding of patch dynamics is important when examining the effects of
fragmentation on wildlife species, because fragmentation essentially restructures the
inherent patch hierarchies and can decrease the diversity of patch hierarchies in the
remaining habitat (Wiens 1976). By determining how patch hierarchies affect foraging
behavior, nest-site selection, and population dynamics, we may be able to better predict
the consequences of habitat fragmentation on wildlife populations.
When investigating habitat associations of an organism over a landscape,
temporal aspects must be considered as well. Data collected represent that landscape at a
5
very discrete place in time as well as in space. For example, the rate of decay and fall of
snags within a stand could drastically alter the quality of that stand from the perspective
of a nesting woodpecker. These dynamics and their effects on the organism of interest
can only be captured by studies that span a longer time period. Studies conducted over a
1 - to 2-year period may represent only a 'snapshot' of reality, and may not represent
'normal' conditions. This may lead the researcher to false conclusions.
Taking into consideration heterogeneity that exists over landscapes, I designed a
study to examine habitat associations of primary cavity-nesters, or woodpeckers, in the
Oregon Cascades. I measured characteristics at multiple scales of resolution that I
thought may be influencing response of woodpeckers over a patchy landscape. To define
patch structure from the perspective of a woodpecker, foraging, nesting and roosting
habitat requirements should be examined. Due to logistical constraints, I chose to focus
my study on associations for nesting habitat, and the conclusions I draw must be framed
within that context.
RESEARCH NEED AND JUSTIFICATION
Primary cavity-nesters create habitat for a suite of secondary cavity-users. About
53 species of birds and small mammals in Oregon use cavities excavated by
woodpeckers, including the mountain bluebird (Sialia cirrucoides), saw-whet owl
(Aegolius acadicus), violet-green swallow (Tycinata bicolor), and northern flying
squirrel (Glaucomys sabrinus) (Bull 1 986a). In addition, recent studies have suggested
that cavities provide critical roosting habitat for several species of bats (Neitro et al. 1985,
Hunter 1990, Ormsbee 1996).
Woodpeckers play a role in maintenance of forest health, by suppressing insect
levels (Otvos 1965). Woodpeckers also initiate and promote decay and nutrient cycling
by excavating in dead trees and down woody material (Bull 1977, Mannan et al. 1980).
They feed primarily on insects found in decaying trees, reducing the loss of wood
products to pest outbreaks (Otvos 1965). Carpenter ants (Camponotus spp.), bark beetles
(Dendroctonus spp.), woodboring beetles (Buprestidae, Cerambycidae.) and Douglas-fir
tussock moths (Orgyia pseudotsuga) are common prey for woodpeckers (Bull 1977).
6
Dead trees, or snags, are a primary resource requirement of woodpeckers (Mannan
et a!. 1980). Woodpeckers select larger diameter snags for foraging, which may be due in
part to the abundance of insects found in larger snags (Mannan et al. 1980, Madsen 1985,
Nelson 1989, Mariani and Manuwal 1990, Weikel 1997). Woodpeckers have been
shown to select the tallest and largest snags available in all forest types and to place nest
cavities at the largest possible diameter above the base of the tree (Mannan et al. 1980,
Raphael and White 1984, Madsen 1985, Mellen 1987, Nelson 1989). Higher nest
location may enhance protection from predators (Nilsson 1984), and weaker excavators,
such as the northern flicker, choose cavities near the top because decay conditions have
sufficiently weakened that portion of the tree to allow excavation (Nelson 1989).
Bull (1 986c) found that woodpeckers prefer dead trees> 35 cm in diameter for
nesting. She defined selection criteria for nest trees based on tree decay, condition,
species, diameter, height and location. Mannan (1977) found that in general, cavitynesters foraged on and nested in Douglas-fir snags averaging more than 60 cm in dbh and
with less than 100% bark cover. Most were> 15 m tall, usually with broken tops, few
branches, and with decayed sapwood and heartwood. Snags of this type were found
primarily in forests over 70 years old, and consequently, populations of cavity-nesters
were concentrated in forested stands 100-200 years old or greater (Mannan 1977).
Nelson (1989) confirmed these findings, showing that densities of cavity-nesting birds
are higher in mature and old-growth forests than in young closed-canopy forests of the
Oregon Coast Range.
Researchers have recommended that habitat plans for cavity-nesters provide tall,
large diameter snags >50 cm dbh within harvest units. Because both species richness and
density have been positively associated with snag density (Schreiber and de Calesta
1992), recommendations provide for maintenance of 3 to 11 large snags per acre
depending on site conditions and geographic location. When and where snag densities
are inadequate to maintain viable populations of cavity-nesters, habitat should be
supplemented by recruiting green trees into the snag population through fungus
innoculation, girdling, or topping.
7
Snag Management
During the past 10-15 years land management agencies have identified snags as
an important limiting resource for woodpeckers in environmental impact statements
(Neitro et a!. 1985). Previously, snags were removed as additional sources of wood fiber
because commercial forestry practices emphasized maximum utilization of the resource
and also because snags and defective trees were seen as potential hazards to workers
involved in tree felling operations (Haapanen 1965, Jackman 1974, Neitro et al. 1985).
Recently, guidelines have been established to ensure that some snags are retained as
wildlife habitat. When snags must be created artificially, snag management can be costly.
Some land management agencies, including the USDA-Forest Service have begun
creating snags for wildlife using a variety of techniques; including topping green trees
using explosives or chainsaws, girdling the tree at the base, or inoculating the tree with a
fungus to promote heart rot (Greg Filip, pers. comm, October 15, 1995.) Each method
shows promise, but more follow-up monitoring needs to be done to assess the success of
these methods. Chambers et al. (1997) monitored snags artificially created by topping in
the Oregon Coast Range to detect usage by cavity-nesters. They found considerable use
of snags by woodpeckers in the first five years following creation. Bull and Partridge
(1986b) reported that topping trees with a saw was the most cost-effective method,
producing trees that stood longer and were used most often by cavity-nesters. Explosives
and herbicides also were tested, but did not appear to be as effective as topping.
Woodpeckers of the Southern Oregon Cascades
The northern flicker (Colaptes auratus), red-breasted sapsucker (Sphyrapicus
ruber) and hairy woodpecker (Picoides villosus) have been described as habitat
generalists, utilizing a wide range of forest types (Madsen 1985, Nelson 1989). Madsen
(1985) found that flickers and hairy woodpeckers generally selected nest sites in open
stand conditions, adjacent to or on the edge of forested areas. Pileated woodpeckers
(Dryocopus pileatus) however, have specific habitat requirements and occupy a narrower
niche within forest ecosystems. They have been found to nest in areas with high tree and
snag density, and require snags with comparatively larger diameters for nesting (Bull
8
1977, 1980, 1986a, 1986c). Madsen (1985) found pileated woodpeckers in unmanaged
stands dominated by old-growth characteristics (e.g., large trees, snags, downed woody
material) or in managed stands where efforts had been made to retain snags.
Comparatively little is known about the nesting and foraging habitat requirements of the
black-backed woodpecker (Picoides arcticus). Nests of black-backed woodpeckers have
been documented in recent burn areas (McClelland 1977). Bull (1980) found this species
predominantly in open ponderosa pine (Pinus ponderosa) forests in eastern Oregon. On
the Diamond Lake Ranger district of southwestern Oregon, nests have been found in both
live and dead lodgepole pine (Pinus contorta) trees (Keith Graves, pers. comm., May 15,
1994).
Significant gaps remain in our knowledge of specific requirements needed by
individual species of woodpeckers with regard to snag size and decay class (Mannan et al.
1980). In order to develop and implement plans that will succeed in maintaining habitat
for woodpeckers, it is critical that we identify what habitat characteristics are used by
woodpeckers.
OBJECTIVES
Within the context outlined above, I developed specific study objectives. The
primary objective of this study was to estimate nest-site characteristics of woodpeckers at
multiple scales in managed forests of the Southern Oregon Cascades. Steps in this
process that contributed to the overall objective included:
•
To estimate nesting habitats of resident woodpeckers including the red-breasted
sapsuckers, black-backed woodpeckers, northern flickers, hairy woodpeckers, and
pileated woodpeckers at the nest-tree, patch, and landscape levels.
•
To determine whether an association existed between percent mature forest and
abundance of woodpecker nests over a landscape, using spatial pattern analysis and
regression analysis.
9
•
To develop models to determine habitat associations of woodpeckers at the nest-tree,
patch, and landscape level.
•
To develop guidelines that can be used in management prescriptions to maintain
habitat for woodpeckers.
LiTERATURE CITED
Bull, E.L. 1977. Habitat utilization of the pileated woodpecker, Blue Mountains,
Oregon. M. S. Thesis. Oregon State University, Corvallis. 58 pp.
Bull, EL. 1980. Resource partitioning among woodpeckers in northeastern Oregon
Ph.D. Dissertation. University of Idaho, Moscow. 109 pp.
Bull, E.L. 1986a. Ecological value of dead trees to cavity-nesting birds in northeastern
Oregon. Oregon Birds 12: 9 1-99.
Bull, E.L. 1986b. Methods of killing trees for use by cavity-nesters. Wildlife
Society Bulletin 14:142-146.
Bull, E.L., S.R. Peterson, and J.W. Thomas. 1986c. Resource partitioning among
woodpeckers in northeastern Oregon. USDA Forest Service Research Note,
PNW-444. 19 pp.
Chambers, C.L., T. Carrigan, T.E. Sabin, J.Tappeiner, and W.C. McComb. 1997. Use of
artificially created Douglas-fir snags by cavity-nesting birds. Western Journal of
Applied Forestry 12:93-97.
den Boer, P.J. 1981. On the survival of populations in a heterogeneous and variable
environment. Oecologia 50: 3 9-53.
Edgerton, P.J. and J.W. Thomas. 1977. Silvicultural options and habitat values in
coniferous forests. Paper presented at the Nongame Bird Habitat Management in
Coniferous Forests of the Western United States, Portland, Oregon. Feb. 7-9,
1977. pp56-65.
Filip, G. Personal Communication. October 15, 1995. Forest pathology expert. Oregon
State University, Corvallis.
10
Forman, R.T. and M. Godron. 1981. Patches and structural components for a
landscape ecology. Bioscience 31: 73 3-740.
Forman, R.T. and M. Godron. 1986. Landscape ecology. John Wiley and Sons, New
York, N.Y. 619 pp.
Franklin, J.F., and R.T. Forman. 1987. Creating landscape patterns by forest
cutting: ecological consequences and principles. Landscape Ecology 1: 5-18
Graves, K. 1995. Personal Comninication. March 15, 1997. USDA Forest Service
Natural Resource Manager, Diamond Lake Ranger District, Umpqua National
Forest.
Haapanen, A. 1965. Bird fauna of the finnish forests in relation to forest succession. I.
Am. Zoo!. Fenn. 2:153-196
Harris, L.D. 1984. The fragmented forest. University of Chicago Press, Chicago,
I.L. 211 pp.
Hunter, M.L. Jr. 1990. Wildlife, forests and forestry: Principles of managing
forests for biological diversity. Prentice-Hall, Inc. Englewood Cliffs, N.J.
Jackman, S.M. 1974. Woodpeckers of the Pacific Northwest; their characteristics and
their role in the forest. M.S. Thesis, Oregon State University, Corvallis. 147 pp.
Kotliar, N.B., and J.A. Wiens. 1990. Multiple scales of patchiness and patch
structure: a hierarchical framework for the study of heterogeneity. Oikos 59:
253-260.
Madsen, S.J. 1985. Habitat use by cavity-nesting birds in the Okanogan National Forest,
Washington. M.S. Thesis. University of Washington, Seattle. 113 pp.
Mannan, R.W. 1977. Use of snags by birds, Douglas-fir region, western Oregon. M.S.
Thesis. Oregon State University, Corvallis. 113 pp.
Mannan, R.W., E.C. Meslow, H.M. Wight. 1980. Use of snags by birds in
Douglas-fir forests, western Oregon. Journal of Wildlife Management 44: 787797.
Mariani, J.M. and D.A. Manuwal. 1990. Factors influencing brown creeper (Certhia
americana) abundance patterns in the southern Washington Cascade Range.
Studies in Avian Biology 13:53-57.
11
McClelland, B.R. 1977. Relationships between hole-nesting birds, forest snags and
decay in western larch, Douglas-fir forests of the northern Rocky Mountains.
Ph.D. Dissertation. University of Montana, Missoula. 495 pp.
McGarigal, K. 1993. Relationship between landscape structure and avian abundance
patterns in the Oregon Coast Range. Ph.D. Dissertation. Oregon State
Corvallis. 273 pp.
Mellen, T.K. 1987. Home range and habitat use by pileated woodpeckers. M.S. Thesis.
Oregon State University, Corvallis. 96 pp.
Naveh, Z. and A. S. Liebermann. 1984. Landscape ecology, theoiy and application.
Springer-Verlag, New York, N.Y. 356 pp.
Nelson, S.K. 1989. Habitat use and densities of cavity-nesting birds in the Oregon
Coast Ranges. M.S. Thesis. Oregon State University, Corvallis. 157 pp.
Neitro, W.A., V.W. Binkley, S.P. Cline, R.W. Mannan, B.G. Marcot, D. Taylor, F.F.
Wagner. 1985. Snags. Pages 129-168 In Brown, E.R. tech. ed. Management of
wildlife and fish habitats in forests of western Oregon and Washington. Part 2 Appendices. USDA Forest Service, Pacific Northwest Region, Portland, OR.
Nilsson, S.G. 1984. The evolution of nest-site selection among hole-nesting birds: the
importance of nest predation and competition. Ornis Scand. 15: 167-175
Ormsbee, P. 1996. Selection of day roosts by female long-legged myotis (Myotis
volans) in forests of the central Oregon Cascades. M.S. Thesis. Oregon State
University, Corvallis. 63 pp.
Otvos, I.S. 1965. Studies on avian predators of Dendroctonus brevicomis le Conte
(Coleoptera: Scolytidae) with special reference to Picidae. Canadian
Entomologist 97: 1184-1199.
Raphael, M.G. and M. White. 1984. Use of snags by cavity-nesting birds in the Sierra
Nevada. Wildlife Monograph No. 86. 66 pp.
Schreiber, B. and D.S. deCalesta. 1992. The relationship between cavity-nesting birds
and snags on clearcuts in wetern Oregon. Forest Ecology and Management 50:
299-3 16.
Van Horne, B. 1983. Density as a misleading indicator of habitat quality. Journal of
Wildlife Management 47:893-901.
12
Weikel, J. 1997. Habitat use by cavity-nesting birds in young thinned and unthinned
Douglas-fir forests of western Oregon. M.S. Thesis, Oregon State University,
Corvallis. 102 pp.
Wiens, J.A. 1976. Population responses to patchy environments. Annual Review of
Ecological Systematics 7: 81-120.
Wiens, J.A. 1989. Spatial Scaling in Ecology. Functional Ecology 3: 385-397.
13
Habitat Associations of Woodpeckers at Multiple Scales in Managed Forests of the
Southern Oregon Cascades
CHAPTER 2
Nest-Site Characteristics of Woodpeckers in Managed Forests
of the Southern Oregon Cascades
INTRODUCTION
Over the past 40 years, the forests of the Pacific Northwest have been managed
for efficient extraction of wood products, using even-aged regeneration methods. Until
the last decade, snags were typically removed for economic, safety or logistic concerns
(Neitro et al. 1985). Removal of snags during logging operations generally has negative
effects on populations of cavity-nesting species (Balda 1975, Thomas Ct al. 1975,
Franzreb 1978, Evans and Conner 1979, Raphael and White 1984, Zarnowitz and
Manuwal 1985).
Primary cavity-excavators and secondary cavity-users depend on dead trees, or
snags for survival; snags are essential for nesting, foraging, and roosting by many species
(Bull 1980, Madsen 1985, Nelson 1989, Schreiber and deCalesta 1992, Bunnell et a!.
1997). Thirty-nine species of birds and 14 species of small mammals in the Pacific
Northwest are dependent on cavities (Neitro et al. 1985, Bull 1986a). Furthermore, the
absence of suitable snags can be a limiting factor for wildlife (Haapanen 1965, Balda
1975, Mannan et al. 1980, Raphael and White 1984). Woodpeckers are primary cavityexcavators, annually excavating fresh cavities for nesting and providing habitat for
secondary cavity-users in the process. Secondary cavity-nesters, including the northern
pygmy owl (Glaucidum gnoma) and the western bluebird (Sialia mexicana), cannot
excavate cavities themselves, but depend upon abandoned woodpecker nest cavities for
nesting and roosting habitat.
Woodpeckers are an integral part of a healthy forest ecosystem, suppressing insect
populations and promoting decay and nutrient cycling by excavating in dead trees (Otvos
14
1965, 1979, 1985; Bull 1977, Mannan et a!. 1980). Woodpeckers have been shown to be
important predators on harmful forest insects such as the western pine beetle
(Dendroctonus brevicomus), the Engelmann spruce beetle (Dendroctonus engelmanni),
and the Douglas-fir tussock moth (Orgyiapseudotsugata) (Knight 1958, Otvos 1965).
Because of their integral role in forest ecosystems, woodpeckers are sometimes
considered to be a keystone species, and a prime indicator of overall forest health
(Bunnell et a!. 1997).
Numerous studies have shown that woodpeckers select snags for nesting and
foraging (Raphael and White 1984, Madsen 1985, Nelson 1989). However, only in the
past 15-20 years have land management agencies considered snags as an important
limiting resource for many wildlife species. Guidelines have been developed and
implemented to ensure that some snags are retained after harvest. Forest Service
regulations require that two hard and one soft snag per acre are left during timber removal
(USDA Forest Service Resource Management Plan 1990). Forest plans recommend that,
whenever possible, snags> 35 cm be left standing following harvest. Neitro et a!. (1985)
recommend leaving 5 snags per hectare, 4.8 of which are soft snags in decay class 4-5,
and 0.2 hard snags, in decay class 2-3. These numbers may be inadequate, however, to
sustain viable populations of cavity-nesters. Hope and McComb (1994) showed that a
majority of biologists in the Pacific Northwest believe that current guidelines for snag
management are inadequate to maintain target populations of woodpeckers.
Important questions remain to be answered regarding specific snag characteristics
preferred by woodpeckers in order to develop management plans that maintain adequate
numbers of suitable snags to sustain populations of woodpeckers. These questions must
not only examine qualities of the snag itself, but also the environment, or immediate
surroundings in which the snag is found. Woodpeckers most likely select snags for
nesting based upon a combination of characteristics including tree-top condition, degree
of hardness, tree species, and presence or absence of various fungi or insect species.
However, woodpeckers probably also consider the characteristics of the surrounding
environment when selecting a snag for nesting. For example, does the snag occur in a
mature forest stand, or is it in the middle of an open meadow? Are there high densities of
15
snags and large amounts of down woody material in the surrounding area or not? If it
occurs in a forested stand, what is the species composition of the trees in the stand?
Additionally, studies are needed to examine the differences between co-existing species
of woodpeckers, to determine the unique characteristics selected for by each species.
Providing habitat to maintain a single species of cavity-nesters may not necessarily meet
the needs of other cavity-nesters.
With these questions in mind, the goals of my study were:
•
To estimate characteristics of nest trees selected by hairy woodpeckers, red-breasted
sapsuckers and northern flickers
•
To determine whether microsites surrounding nest trees were associated with nest-site
selection by woodpeckers
STUDY AREA
The study was conducted in the Central Oregon Cascade Range, on the Diamond
Lake Ranger District of the Umpqua National Forest. Study sites are located
approximately 70 miles east of Roseburg, Oregon, in Douglas County between 47° 54'
and 47° 56' latitude (Fig. 1). Study sites were within the Umpqua National Forest on
sites varying in elevation from 1066 m-1463 m in the Umpqua High Cascade sub-
province. The climate is characterized by moderate temperatures, wet, mild winters and
relatively cool, dry summers (Franklin and Dyrness 1988). The region receives an
average of 152 cm of precipitation annually; of which 75-85% occurs between October
and April, primarily as rain, with snow at high elevations (Azet and McCrimmon 1990).
The study area is located within the western hemlock (Tsuga heterophylla) zone,
the most extensive vegetation zone found in the Pacific Northwest (Franklin and Dyrness
1988). In this zone western hemlock is considered the climax species, but this state is
rarely reached due to forest management activities (Harris 1984). The overstory is
typically dominated by Douglas-fir (Pseudotsuga menziesii), though white fir (Abies
concolor), western hemlock, mountain hemlock (Tsuga mertensiana), Pacific silver fir
(Abies amabilis), Pacific yew (Taxus
commonly occur.
and Shasta red fir (Abies
16
Figure 1. Location of study sites for woodpecker habitat association
study on the Diamond Lake Ranger District, Umpqua National Forest
Southern Oregon Cascades.
STUDY SITE LOCATION
Sites
Figure
1.
,col.
0
Uometei
30
18
Other species present include: incense-cedar (Calocedrus decurrens), western redcedar
(Thuja plicata), ponderosa pine (Pinus ponderosa) and sugar pine (Pinus lambertiana).
Lodgepole pine (Pinus contorta) is found in sites located on the eastern end of the study
area. Understory vegetation varies depending on microsite conditions, but generally is
dominated by golden chinquapin (Castanopsis chrysophylla), Sitka alder (Alnus sinuata),
Pacific rhododendron (Rhododendron macrophyllum) and vine maple (Acer circinatum).
Buckrush (Ceanothus integerrimus), and snowbrush (Ceanothus velutinus) are found in
young, regenerating stands. Ground cover is variable and includes sword fern
(Polystichum
bracken fern (Pteridium aquilinum), vanillaleaf (Achlys
triphylla), Cascade Oregon-grape (Berberis nervosa), huckleberries ( Vaccinium spp.),
salal (Gaultheria shallon), and prince's pine (Chimophila umbellata).
The study sites were dominated by mixed-conifer forest composed of at least
70%, but not more than 85% Douglas-fir trees. The remaining trees were a mixture of
western hemlock, mountain hemlock, true fir, and pine trees. Three sites had a small
component of lodgepole pine, not exceeding more than 5% of the total area. The sites
were at approximately the same elevation.
Volcanic activity has influenced landscape formation found in the study area,
depositing a layer of pumice across the landscape. Prior to European settlement in the
middle 19th century, the natural disturbance regime of the area was dominated by wild
fire events. Since its designation as National Forest land in 1905, the resource planning
strategy has emphasized efficient timber production, using even-aged management
methods. Due to management practices over the past 40 years, the condition of the
landscape is highly variable, consisting of a mosaic of habitat patches of varying age and
structure.
Five species of woodpeckers are known to breed within the study area; the blackbacked woodpecker, hairy woodpecker, northern flicker, pileated woodpecker, and red-
breasted sapsucker. Other species of woodpecker, including red-naped sapsuckers
(Sphyrapicus nuchalis) and white-headed woodpeckers (Picoides albolarvatus) are
residents on the east side of the Cascade Range, but occur only occasionally in the study
area.
19
METHODS
Study Site Selection
Eleven sites within the study area were selected for the study. Site selection
criteria were based on the proportion of the area comprised of mature forest, defined as
closed-canopy forest with> 40% canopy cover and trees averaging 53 cm in diameter.
The proportion of total forested area within study sites varied from 10% to 94%. The
remaining sites had intermediate amounts of forest, with the intent to select sites that
represented a continuum of amount of forest cover. Six sites were surveyed in 1995, and
seven in 1996; two of the sites sampled in 1995 were resampled in 1996.
Study sites chosen for woodpecker sampling were 200-ha in size. Home range
estimates of resident woodpeckers range from 12 ha for the red-breasted sapsucker to 200
ha for the pileated woodpecker (Bull 1977, Mannan et al. 1980, Brown et al. 1985,
Winkler et a!. 1995). I chose 200-ha study sites because they were sufficiently large to
include multiple woodpecker home ranges, yet small enough to meet logistical
constraints.
Bird Sampling and Nest Searches
A 1600- x 1200-rn grid was established at each study site. Five, transect lines
were located parallel to one another within each grid, with stations established every 200
meters along transect lines. Station points were used as references for recording
locations of nests.
I located woodpecker nests by walking along transect lines. Approximately every
200 meters I stopped to listen for woodpeckers. I attempted to visually locate each
woodpecker heard. Once located, I observed bird behavior, looking for evidence of a
nest. Indicators of nest presence included wood chips at the base of a tree, drumming
between pair members, territorial calling, and begging calls of nestlings. I followed
woodpeckers for as long as possible or until a nest was discovered. Woodpeckers were
not followed if they left the study site. Woodpeckers were easier to locate in opencanopy than in closed-canopy forest conditions, where they are more visible. I used the
20
relative amount of closed-canopy forest present in a transect to standardize search time.
To minimize potential sampling biases, I allotted approximately twice the amount of time
to conduct searches in closed-canopy than I did in open-canopy forest.
All sites were visited a minimum of five times between 10 April and 14 July in
1995 and 1996, with 6 sites sampled in 1995 and 7 in 1996. Surveys were conducted
between 0500 and 1500. Potential nests were marked and later revisited to confirm
nesting status. Nests were considered to be confirmed when members of a pair were
observed excavating a cavity, exchanging incubation duties, or feeding fledglings at a
cavity entrance, or when fledglings were seen or heard in the cavity.
Habitat Sampling
Nest Trees--For each nest tree I recorded species, height, diameter at breast height
(dbh), condition (broken or unbroken top), decay class from 1-5 based on Cline et al.
1980, and height and orientation of nest (Table 1). Tree and nest height were measured
with a clinometer, dbh with a diameter tape, and cavity orientation by compass. I
visually estimated bark cover as percentage of bark remaining. Canopy cover was
measured using a moosehorn (Garrison 1949). I recorded readings at 6 bearings 6 meters
from the base of the tree and calculated the average to obtain an estimate of percentage
overstory canopy. In addition, cover was estimated visually to the nearest 5% at five
different canopy heights; 0-5, 5-10, 10-20, 20-30, and >30 m above the ground.
I collected data on ground cover composition, densities of shrubs and trees, and
canopy cover in a 0.04-ha plot surrounding each nest tree. Trees and shrubs were counted
and species and dbh of all stems >10 cm dbh were measured. Snags greater than 10 cm
in diameter were recorded; species was recorded if it could be determined. I visually
estimated percent cover of shrub, herbaceous material, bare ground, and litter.
Random plots--To sample random snags, I selected a random compass bearing
and distance within the home-range of the nesting bird. Using the nest tree as the starting
point, the random bearing and distance were followed until arriving at the designated
point. The nearest snag to that point was selected for habitat analysis. Data collected for
21
Table 1. Definition of habitat characteristics measured in plots centered around
woodpecker nest trees and random trees.
Habitat Variable
Description
Tree diameter
Diameter at breast height (cm)
Tree height
Height of tree (m)
Nest height
Height of nest (m)
Nest cavity orientation
Direction of cavity opening (degrees)
Tree top condition
Top intact or broken
Decay stage
Category from 1-5 (Cline et al. 1980)
Bark
Percentage of bark remaining on bole
Cavity
Number of visible nest cavities on tree
Plot stems
Measure of diameter and species for live
tree stems> 10 cm within 0.04-ha plot
Stand density index (SDI)
Reineke's index of stand density
accounting for average tree size and density
in the 0.04-ha plot (Mctague and Patton
1989)
Mean diameter of plot stems
Calculation of mean diameter of all trees in
0.04-ha plot
Vertical structure
Percent foliage in 5 vertical layers from 070 m
Canopy cover
Mean percent of overstory canopy cover in
0.04-ha plot
Ground cover
Percent cover of ground vegetation (all
species)
22
nest trees and vegetation characteristics of random plots were identical to those recorded
for nest trees.
Data Analysis
I performed analyses that compared habitat characteristics of nest sites to those of
random sites for hairy woodpeckers, red-breasted sapsuckers and northern flickers.
Sample sizes for pileated woodpeckers (n=8), red-naped sapsuckers (n1), and blackbacked woodpeckers (n=1) were inadequate to analyze statistically. Variables were
analyzed using PROC UN! VARIATE (SAS Institute, Inc. 1990) to obtain means, ranges,
and standard deviations. Univariate tests showed that many of the variables were not
normally distributed. In addition, many of the variables were categorical, with 2 to 4
levels of response. Categorical data are common among habitat association studies, and
are best analyzed by using multivariate techniques (Ramsey et a!. 1994). Multiple
logistic regression was chosen for analysis. Logistic regression allows habitat variables
to be measured on continuous scales, and, unlike discriminant function and rank-based
tests, is not sensitive to non-normality (Ramsey et al. 1994). I used PROC GENMOD
(SAS Institute, Inc. 1997) to perform logistic regression. The procedure fits a generalized
linear model to the data using maximum likelihood estimations of parameters.
To begin the process of variable selection, variables were considered based on
likely biological relevancy to cavity-nesters. Correlation analysis revealed that diameter
and tree height were highly correlated (r = 0.62); and height was dropped from the
analysis because dbh has been shown to be a stronger indicator of suitable habitat for
woodpeckers (Nelson 1989). I pooled tree species into four categories: Douglas-fir,
white fir, hemlock, and other. The "hemlock" category included mountain and western
hemlock, and "other" included pines (ponderosa, lodgepole, and western white) and true
firs other than white fir (Shasta red, Pacific silver fir). This categorization was done to
give the model greater power in detecting differences between nests and random trees.
I performed logistic regression analysis for each species of woodpecker independently. I
constructed single-variable logistic models using each independent variable and used the
23
drop-in-deviance test (Hosmer and Lemeshow 1989) to determine the amount of variance
accounted for by each variable. The model that had the greatest significant drop in
deviance was chosen. This process was repeated iteratively, adding additional variables
one at a time to the model. Variables resulting in the greatest drop-in-deviance were
added to the model if they were significant at the P <0.05 level. In this manner, a model
was developed for each woodpecker species predicting the probability of use of a
particular tree for nesting. Although models for different species of woodpeckers are not
directly comparable to one another, the results identify the suite of variables most closely
associated with each species in nest-site selection.
Selection of random trees was 'matched' to nest trees. This design was used to
eliminate some of the extraneous variation inherent in a study of this magnitude. Because
logistic regression assumes samples are not paired, I also used an alternative approach
that is commonly used in matched case-control studies, in which the dependent variable
is stratified based on the variables believed to be associated with the outcome (Hosmer
and Lemeshow 1989). My study could be interpreted as a matched-case study, in which
the dependent variable NEST, is stratified based on a definable area, in this case home
range. The design was developed for more practical reasons, however, it made sense
biologically, and therefore is not truly a paired design. Therefore, I performed the final
analysis using logistic regression.
The results of this analysis and those of the logistic regression analysis are
essentially identical, and only the results of logistic regression are presented here.
RESULTS
I observed seven species of primary cavity-excavators in the study area during the
1995-1996 breeding seasons. I found 91 nests of woodpeckers in 1995, and 82 nests of
woodpeckers in 1996 (Table 2).
24
Table 2. Number of nests of woodpeckers found during 1995-96 breeding
seasons in 11 study-sites located in the Southern Oregon Cascades.
Total
Number
Number
nests-1995
nests-1996
Red-naped sapsucker
0
1
1
Red-breasted sapsucker
36
32
68
Hairy woodpecker
14
18
32
1
0
1
35
28
63
0
0
5
2
7
91
82
173
Woodpecker Species
Black-backed woodpecker
Northern flicker
White-headed woodpeckerb
Pileated woodpecker
Totals
b
Two individuals were observed at Bear Site, no nests were located
Characteristics of Nest Trees
Tree diameter and height- Woodpeckers nested primarily in large-diameter, dead
trees (Fig. 2). The average diameter for nest trees was 79 cm, varying only slightly
among species (Table 3). Mean height of nest trees was 24.6 m, with a range of 4-80 m.
Tree diameter and tree height were highly correlated (r= 0.62). Mean nest height was 18
m and although this number varied among species, the variation was not statistically
significant (Table 3).
Tree condition- Eighty-six percent of all nests were found in dead trees, and all of
the live trees with nests showed visible signs of decay. Usually a portion of the tree was
dead or diseased, suggesting the presence of some type of fungal rot, or previous injury to
the tree.
25
60
50
0
0
(9
0
0
V
0
0
(0
0
0
(0
It
0
0
0
0
A
•
• West
U Random
Diameter (cm)
Figure 2. Diameter of woodpecker nest trees versus random trees.
100
90
80
• Broken
Ulniact
©
40
30
20
10
0
HAWO
Nest
RBSA
NOFL
RAND
tree and random trees
Figure 3. Tree-top condition for hairy woodpeckers, red-breasted
sapsuckers, northern flickers and random trees.
26
All species most frequently used trees with broken tops: 81% of nest trees of red-
breasted sapsuckers and hairy woodpeckers and 94% of nest trees of northern flickers had
broken tops. Flickers used broken-top snags the majority of the time, with 94% of all
nests found in trees with broken tops. Only 4 out of 63 northern flicker nest trees had
intact tops(Fig. 3).
Decay- Of 163 nest trees, 14% were in decay stage 1,45% in decay stage 2 and
30% in decay stage 3; and 10% in decay stage 4 trees. There were differences in pattern
of use of snags in different decay stages among species of woodpeckers (Fig. 4). Twentytwo percent of nests of red-breasted sapsuckers were in decay stage 1 trees, and only 910% of nests of hairy woodpeckers and northern flickers were in decay stage 1 trees.
Nests of red-breasted sapsuckers were almost exclusively in hard trees, 98% of nests of
this species were found in decay stage 1, 2, or 3 trees. Nest trees of hairy woodpeckers
were typically of intermediate hardness; 82% of nests of this species were found in trees
in decay stages 2 or 3, 9% were in decay stage 1 trees, and 9% were in trees of decay
stage 4. Northern flickers used soft snags for nesting; 32% of nests were located in trees
in decay stage 3 and 17% were found in decay stage 4 trees. Of the remaining nests, 10%
were in decay stage 1 trees, and 41% in snags in decay stage 2.
Tree species-Douglas-fir was most often used for nesting by cavity-nesters; 47%
of all nest cavities were located in Douglas-fir, 25% of the nests were in white fir trees,
and 15% were in hemlock trees (Fig. 5). The remaining nests occurred in pine and other
species of true fir besides white fir. There were not any notable differences among
species of woodpeckers in pattern of use of tree species.
Multivariate analysis
Red-breasted sapsucker- Trees used by red-breasted sapsuckers for nesting were
larger in diameter than random trees. Nest trees had a mean dbh of 80.5 cm whereas the
mean dbh of random trees was 42.1 cm. The logistic regression model predicted that redbreasted sapsuckers were 10.5 times more likely to use a tree for nesting for each 10 cm
increase in diameter (P < 0.000 1) (Table 4). Sapsuckers nested more frequently in trees
27
Table 3. Mean values of nest tree characteristics for hairy woodpeckers, northern
flickers and red-breasted sapsuckers. Standard deviations are reported (below the
mean values).
VARIABLE
Diameter (cm)
.
Height (m)
Height of nest
(m)
Bark
remaining
Number of
cavities
Hairy
woodpecker
Northern
flicker
Red-breasted
sapsucker
Random
Trees
(n=32)
80.4
77.7
80.5
42.1
(31.4)
(31.3)
(28.7)
(31.9)
28.0
19.7
27.5
15.2
(16.4)
(12.8)
(12.3)
(12.9)
18.6
14.3
20.4
N/A
(12.6)
(10.8)
(10.3)
68.5
66.7
90.3
69.0
(38.0)
(36.6)
(21.9)
(38.6)
5.5
5.9
8.1
0.85
(5.2)
(7.5)
(8.1)
(2.7)
.
28
IHAWO
• ABSA
•NOFL
•RAND
Decay 1
Decay 2
Decay 3
Decay 4
Decay Class
Figure 4. Decay class for hairy woodpeckers, red-breasted sapsuckers,
northern flickers and random trees.
50
I HAWO
•RBSA
BNOFL
•RAND
Ui
0
C.)
Cl)
C.)
0
I
Ui
Tree species
Figure 5. Tree species for nests of hairy woodpeckers, red-breasted
sapsuckers, northern flickers and random trees.
29
with broken tops than in those with intact tops (P <0.0108). Trees with broken tops were
2.6 times more likely to be used for nesting by red-breasted sapsuckers than were those
with intact tops. All characteristics measured at the plot level were insignificant. After
accounting for dbh and tree-top condition, sapsuckers did not seem to be using trees for
nesting based on vegetation composition and structure within a 0.04-ha area around the
nest.
Table 4. Results of multiple logistic regression comparing tree characteristics for nests
of red-breasted sapsuckers compared to random trees. Variables are presented in the
order in which they appeared in the model, and probability of use is based upon specified
parameters. n68.
Coefficient
SE
Prob>
Condition
of use
Chi
Intercept
-2.60
0.5599
0.0001
Dbh
0.052
0.0092
0.0001
Tree-top
condition
-1.38
0.5403
0.01
Probability
10 cm increase in
dbh
10.5-fold
increase
Broken-top
2.6-fold
increase
Hairy woodDecker- Diameter and decay class significantly distinguished nest trees
of hairy woodpeckers from random trees. Mean diameter of nest trees was 80.4 cm
versus 42.1 cm for randomly selected trees. Hairy woodpeckers were 10.4 times more
likely to select a nest tree for every 10 cm increase in diameter (P < 0.0001) (Table 5).
Trees in decay stage three were 16.4 times more likely to be selected for use by nesting
hairy woodpeckers over trees in decay stage 4 (P <0.0077). After accounting for dbh and
decay class, I could not detect any significant habitat relationships at the plot level.
30
Statistical analysis did not reveal any other habitat characteristics that were significantly
associated with nest-site selection for hairy woodpeckers.
Table 5. Results of multiple logistic regression comparing tree characteristics for nests
of hairy woodpeckers compared to random trees. Variables are presented in the order in
which they appeared in the model, and probability of use is based upon specified
parameters. n=32.
Coefficient
SE
Prob>
Condition
Probability
of use
Chi
Intercept
-3.97
-1.18
0.0008
Dbh
0.04
0.01
0.0003
10 cm increase in
dbh
10.4-fold
increase
Decay
2.84
1.07
0.008
Decay stage 3 tree
16.4-fold
increase
31
Northern flicker- As with the red-breasted sapsuckers, northern flickers selected
nest trees based on tree diameter and tree top condition. The model predicted a 10.2-fold
increase in probability of use for each 10 cm increase in diameter (P <0.0001) (Table 6).
Northern flickers are 4.3 times more likely to use a tree with a broken top (P <0.001).
Logistic regression did not detect any other nest level characteristics significant in
predicting use by flickers.
Table 6. Results of multiple logistic regression comparing tree characteristics for nests
of northern flickers compared to random trees. Variables are presented in the order in
which they appeared in the model, and probability of use is based upon specified
parameters. n=63.
Coefficient
SE
Prob>
Condition
Probability
of use
Chi
Intercept
-1.11
0.4980
0.025
Dbh
0.02
0.0070
0.0004
10 cm increase in
dbh
10.2-fold
increase
0.001
Broken-top
4.3-fold
increase
.
Tree-top
condition
-2.06
0.6304
Tree species
I did not detect any significant pattern of use of tree species by individual
woodpeckers. The sample size may have been insufficient to detect any differences if
they did exist.
32
DISCUSSION
Woodpeckers select nest trees based on a combination of characteristics that make
a tree suitable for nesting. The 'ideal' tree is not characterized solely by one component,
but by the presence and interaction of several factors. Qualities that describe tree
suitability from the perspective of a woodpecker are tree species, diameter and height,
wood hardness, tree-top condition, and the amount and integrity of the bark cover.
Diameter
Woodpeckers selected large diameter trees for nesting. Less than 3% of all nest
trees were smaller than 30 cm in diameter. My results are consistent with other studies
conducted in the Pacific Northwest that have reported woodpeckers using large-diameter
trees for nesting (Madsen 1985, Mannan et al. 1980, Raphael and White 1984, Nelson
1989, Lundquist and Mariani 1991, Schreiber and deCalesta 1992).
There are several hypotheses that may explain selection of large-diameter trees by
woodpeckers. Woodpeckers require a tree large enough to allow excavation of a cavity
suitable for the nesting bird. Cavity dimensions of nests of the red-breasted sapsucker
range from 15-25 cm in depth, and 10-13 cm in width; northern flicker nest cavities
average 46 cm deep by 20 cm wide, but have been recorded as large as 60 by 15 cm; and
nest cavities of hairy woodpeckers range from 25 to 30.4 cm in depth (Bent 1964).
Woodpeckers are most likely restricted to nesting in larger trees that can accommodate
cavities of the appropriate dimensions. Large trees also provide increased protection
from severe weather conditions and enhance thermal insulating capabilities (Beebe 1974,
Jackman 1974, Karisson and Nilsson 1977, Conner 1979). In March and April, when
woodpeckers are beginning to excavate nests in the Oregon Cascades, snow is not
uncommon, the weather conditions are often cold and wet for extended periods, and the
greater insulation provided by larger trees may increase the chance of nest success.
In my study, diameter was confounded with height, suggesting that woodpeckers
are using trees that are taller than average and have large diameters. Tall trees allow
woodpeckers to place nest cavities further from the ground, offering better protection
33
from potential predators such as pine martens (Martes americana) and weasels (Mustela);
(Nilsson 1984, Gutzwiller and Anderson 1987).
In addition to their importance as potential nest trees, large snags support greater
densities of insects, a primary food source for woodpeckers. Cline (1977) reported higher
concentrations of beetles and carpenter ants (Componotus spp) in larger snags. Mariani
and Manuwal (1990) reported an increase in abundance of arthropods to increased tree
diameter and bark furrow depth. Weikel (1997) emphasized the importance of
maintaining large snags as foraging substrate for hairy woodpeckers and other cavity-
nesters in the Oregon Coast Range. Based on my results, I hypothesize that nest-site
selection is strongly influenced by tree diameter, not only as a nesting substrate, but also
because of enhanced foraging opportunities and the increased protection from predation.
Currently, land management agencies base much of their snag management on the
habitat needs of the pileated woodpecker. The pileated woodpecker is considered to be a
forest indicator species, selecting older forest with greater canopy cover for nesting, and
utilizing large snags for nesting, roosting, and foraging (Bull 1977, Bull 1980, Madsen
1985, Mellen 1987, Nelson 1989. It is assumed that by providing habitat for the pileated
woodpecker, the habitat needs of other woodpeckers and secondary cavity-users will
subsequently be met. Snag management guidelines presented in the Northwest Forest
Plan (USDA Forest Service and USD1 Bureau of Land Management 1994) require that
adequate numbers of snags are retained to support 40% of the potential population of
pileated woodpeckers. The Northwest Forest Plan requires that 5 hard snags (decay stage
1-2) and 0.3 soft snags (decay stage 3-4) per hectare greater than 35 cm in diameter are
left after harvest (USDA Forest Service and USD1 Bureau of Land Management 1994).
There is strong evidence, however, that all woodpeckers select snags significantly larger
than 35 cm in diameter for nesting (Bull 1977, Bull 1980, Raphael and White 1984,
Zarnowitz and Manuwal 1985, Madsen 1985, Nelson 1989, Lundquist and Mariani 1991,
Schreiber and deCalesta 1992, Bunnell et al. 1997, this study), and that large snags
additionally provide important resources for foraging (Weikel 1997). Emphasis should
be placed on managing forests to provide and maintain larger snags, not only because
they are more desirable for nesting and foraging, but because they remain standing
34
longer, and are able to provide habitat over a longer period of time (Cline et a!. 1980,
Neitro et al. 1985, Raphael and Morrison 1987).
Tree Condition and Decay
Considerable emphasis has been placed on size of snag and its importance to
nesting woodpeckers. The state of deterioration of a snag is also critical; unless sufficient
rot is present, a tree is unusable by woodpeckers. Mannan et al. (1980), reported that
woodpeckers in western Oregon nested most frequently in trees of decay stage 3.
Lundquist and Mariani (1991) found that cavity-nesters used harder snags in the
Washington Cascades, but mentioned that most nest holes were located in the tops of
snags, where decay and rot were present. I found that red-breasted sapsuckers used
harder snags in decay classes 1-2 for nesting, hairy woodpeckers used trees in the
intermediate stages of decay, and northern flickers used trees that were well-decayed.
These results suggest that it is important to maintain snags representing a range of decay
stages to provide nesting habitat for woodpeckers.
The heartwood of a tree must be sufficiently decayed for woodpeckers to excavate
nest cavities (Conner et al. 1976, Bent 1964, Mannan et al. 1980). Location of the
original source of decay, along with weather and other environmental factors influence
the dynamics driving tree deterioration (Cline et al. 1980, Neitro et al. 1985). Snag
deterioration is initiated by invasion of insects, fungi and bacteria, promoted by weather
conditions and accentuated by age (Kimmey and Fumiss 1943). This process differs
among individual tree species; for Douglas-fir, the decay generally proceeds from top to
bottom, and outer to inner bole (Wright and Harvey 1967). In my study, 86% of all nest
trees and snags had broken tops. Broken tops serve as an entrance portal for disease and
fungal growth (McClelland and Frissell 1975) and can accelerate deterioration of
heartwood to the point where it is suitable for excavation.
Tree Species
I found woodpeckers nesting primarily in Douglas-fir and white fir trees;
however, I could not detect any disproportionate use of tree species by any of the three
35
species
of woodpecker studied. In Oregon, several studies have indicated that cavity-
nesters use Douglas-fir trees for nesting more than would be expected based on
availability (Nelson 1989, Mannan Ct al. 1980). In the southern Cascades of Washington,
Lundquist and Mariani (1991) and Madsen (1985) reported disproportionate use by
woodpeckers of western white pine. It may be the case in my study that sample size
limited the ability of the statistical test to detect any differences between tree species for
nest trees and random trees. Selection of tree species for nesting is probably influenced
by local factors, such as presence of absence of fungal disease, insects, and regional
climatic conditions.
CONCLUSIONS
Tree characteristics influence nest-site selection by woodpeckers in the Southern
Oregon Cascades. Tree diameter, tree-top condition, and decay stage all appeared to
influence use of trees by woodpeckers for nesting. Large diameter trees were associated
with nests of all three species; the hairy woodpecker, northern flicker, and red-breasted
sapsucker. Tree-top condition was associated with northern flickers and red-breasted
sapsuckers. These species nested more often in trees with broken tops than in trees with
intact tops. Nests of hairy woodpeckers were associated with soft snags in decay class 3.
Although I found that differences in structure and condition of snags influenced
use by woodpeckers, I concluded from my results that variation within the surrounding
microsite did not appear to affect nest-site-selection by woodpeckers. I then modified my
scale of resolution, to examine nest-site selection at a larger spatial scale, and determine
whether characteristics at the landscape level had any association with nest-site selection
by woodpeckers. The results of the landscape level study are presented in the Chapter 3:
Habitat Associations of Woodpeckers at the Landscape level in Managed Forests of the
Southern Oregon Cascades
36
LiTERATURE CiTED
Azet, T. L.A. McCrimmon. 1990. Preliminaiy Plant Association of the Southern
Oregon Cascade Mountain Province. USDA Forest Service Publication. Siskiyou
National Forest. 113 pp.
Balda, R.P. 1975. The relationships of secondary cavity-nesters to snag densities in
western coniferous forests. USDA Forest Service Wildlife Technical
Bulletin 1, Albuquerque, N.M. 37 pp.
Beebe, S.B. 1974. Relationships between insectivorous hole-nesting birds and forest
management. Yale University School of Forestry and Environmental Studies.
49 pp.
Bent, A.C. 1964. Life Histories of North American woodpeckers. Dover Publications.
New York, N.Y. 334 pp.
Brown, E.R. tech. ed. 1985. Management of wildlife and fish habitats in forests of
western Oregon and Washington. Part 2 Appendices. USDA Forest Service,
General Technical Report PNW-R8-F&WL-192-1985. Portland, OR. 302 pp.
Bull, E.L. 1977. Habitat utilization of the pileated woodpecker, Blue Mountains,
Oregon. M. S. Thesis. Oregon State University, Corvallis. 58 pp.
Bull, E.L. 1980. Resource partitioning among woodpeckers in northeastern Oregon
Ph.D. Dissertation. University of Idaho, Moscow. 109 pp.
Bull, E.L. 1986a. Ecological value of dead trees to cavity-nesting birds in northeastern
Oregon. Oregon Birds: 12: 9 1-99.
Bunnell, F. L., L.L. Kremsater, R.W. Wells. 1997. Likely consequences of forest
management on terrestrial, forest-dwelling vertebrates in Oregon. Report M-7 of
the Centre for Applied Conservation Biology, University of British Columbia.
129 pp.
Cline, S.P. 1977. The characteristics and dynamics of snags in Douglas-fir forests of the
Oregon Coast Range. M.S. thesis. Oregon State University, Corvallis. 107 pp.
Cline, S.P., A.B. Berg, and H.M. Wight. 1980. Snag characteristics and dynamics in
Douglas-fir forests, western Oregon. Journal of Wildlife Management 44: 773786.
37
Conner, RN., O.K. Miller, C.S. Adkisson. 1976. Woodpecker dependence on trees
infected by fungal heart rots. Wilson Bulletin 88: 575-581.
Conner, R.N. 1979. Seasonal changes in woodpecker foraging methods: strategies for
winter survival. Pages 95-105 In: J.G. Dickson, R.N. Conner, R.R. Fleet, eds.
The role of insectivorous birds in forest ecosystems: Proc. of a symposium.
Nacogdoches,Texas. Academic Press, Inc. New York, N.Y.
Evans, K., and R.N. Conner. 1979. Snag management. pages 2 14-225 R.M. DeGraaf
and K.E. Evans, eds. Management of north central and northeastern forests for
nongame birds. USDA Forest Service General Technical Report NC-5 1, St. Paul,
M.N.
Franklin, J.F., C.T. Dryness. 1988. Natural vegetation of Oregon and Washington.
Oregon State University Press, Corvallis. 452 pp.
Franzreb, K.E. and R.D. Ohmart. 1978. The effects of timber harvesting on
breeding birds in a mixed coniferous forest. Condor 80: 431 -441.
Garrison, G.A. 1949. Uses and modifications for moosehorn crown closure estimation.
Journal of Forestry 47: 733-735.
Gutzwiller, K.J. and S.H. Anderson. 1987. Multiscale associations between cavitynesting birds and features of Wyoming streamside woodlands. Condor 89: 534548.
Haapanen, A. 1965. Bird fauna of the finnish forests in relation to forest succession. I.
Am. Zool. Fenn. 2:153-196
Harris, L.D. 1984. The fragmented forest. University of Chicago Press, Chicago,
I.L. 211 pp.
Hope, S. and W.C. McComb. 1994. Perceptions of implementing and monitoring
wildlife tree prescriptions on national forests in western Washington and Oregon.
Wildlife Society Bulletin 22: 383-392.
Hosmer, D.W. Jr, and S. Lemeshow. 1989. Applied logistic regression. John Wiley
and Sons, New York, N.Y. 307 pp.
Jackman, S.M. 1974. Woodpeckers of the Pacific Northwest; their characteristics and
their role in the forest. M.S. Thesis, Oregon State University, Corvallis. 147 pp.
Karlsson, J. and S.G. Nilsson. 1977. The influence of nest-box area on clutch size in
some hole-nesting birds. Ibis 119: 207-211.
38
Kimmey, J.W. and R.L. Furniss. 1943. Deterioration of fire-killed Douglas-fir. USDA
Technical Bulletin 351. U.S. Governmen Printing Office. Washington, D.C.
61 pp.
Knight, F.B. 1958. The effects of woodpeckers on populations of the Engelmann spruce
beetle. Journal of Economic Entomology 51: 603-607.
Lundquist R.W. and J.M. Mariani. 1991. Nesting habitat and abundance of snagdependent birds in the southern Washington Cascade Range. Pages 22 1-239 jjj L.
F. Ruggiero, K.B. Aubry, A.B. Carey, and M.H. Huff, tech. coords., Wildlife and
vegetation of umnanaged Douglas-fir forests. USDA Forest Service General
Technical Report PNW-GTR-285.
Madsen, S.J. 1985. Habitat use by cavity-nesting birds in the Okanogan National Forest,
Washington. M.S. Thesis. University of Washington, Seattle. 113 pp.
Mannan, R.W., E.C. Meslow, H.M. Wight. 1980. Use of snags by birds in
Douglas-fir forests, western Oregon. Journal of Wildlife Management 44: 787797.
Mariani, J.M. and D.A. Manuwal. 1990. Factors influencing brown creeper (Certhia
americana) abundance patterns in the southern Washington Cascade Range.
Studies in Avian Biology No. 13:53-57.
McClelland, B.R. and S.S. Frissell. 1975. Identifying forest snags useful for holenesting birds. Journal of Forestry 73: 414-417.
Mellen, T.K. 1987. Home range and habitat use by pileated woodpeckers. M.S. Thesis.
Oregon State University, Corvallis. 96 pp.
Nelson, S.K. 1989. Habitat use and densities of cavity-nesting birds in the Oregon
Coast Ranges. M.S. Thesis. Oregon State University, Corvallis. 157 pp.
Neitro, W.A., V.W. Binkley, S.P. Cline, R.W. Mannan, B.G. Marcot, D. Taylor, F.F.
Wagner. 1985. Snags. Pages 129-168 In Brown, E.R. tech. ed. Management of
wildlife and fish habitats in forests of western Oregon and Washington. Part 2 Appendices. USDA Forest Service, Pacific Northwest Region, Portland, OR.
Nilsson, S.G. 1984. The evolution of nest-site selection among hole-nesting birds: the
importance of nest predation and competition. Ornis Scand. 15: 167-175
Otvos, I.S. 1965. Studies on avian predators of Dendroctonus brevicomis le Conte
(Coleoptera: Scolytidae) with special reference to Picidae. Canadian
Entomologist 97: 1184-1199.
________
39
1979. The effects of insectivorous bird activities in forest ecosystems: an
J.G. Dickson et aL, eds. The role of insectivorous
evaluation. Pages 341-374
birds in forest ecosystems. Academic Press. New York, N.Y.
Otvos, I.S. and R.W. Stark. 1985. Arthropod food of some forest-inhabiting birds. The
Cannadian Entomologist 117:971-990
Ramsey, F.L., Marti McCracken, J.A. Crawford, M.S. Drut and W.J. Ripple. 1994.
Habitat association studies of the northern spotted owl, sage grouse, and
flammulated owl. Pages 189-209 In N. Lange, L. Ryan, L. Billard, D. Brillinger,
Conquest and J. Greenhouse (eds.). Case Studies in Biometry. John Wiley and
Sons, New York, N.Y. 496 pp.
Raphael, M.G. and M. White. 1984. Use of snags by cavity-nesting birds in the Sierra
Nevada. Wildlife Monograph No. 86. 66 pp.
Raphael, M.G. and M.L. Morrison. 1987. Decay and dynamics of snags in the
Sierra Nevada, California. Forest Science 33: 774-783.
SAS Institute, Inc. 1990. SAS/STAT Procedures Guide, Version 6, Third Edition, Cary,
NC:. '705 pp.
1997.
SAS/STAT software: changes and enhancements through release 6.12.
Cary,N.C. :ll67pp.
Schreiber, B. and D.S. deCalesta. 1992. The relationship between cavity-nesting birds
and snags on clearcuts in wetern Oregon. Forest Ecology and Management 50:
299-316.
Thomas, J.W., G.L. Crouch, R.S. Bumstead, and L.D. Bryant. 1975. Silvicultural
Proc. symposium
options and habitat values in coniferous forests.
management of forest and range habitats for nongame birds. USDA Forest
Service General Technical Report W0-1.
USDA Forest Service. 1990. Land and Resource Management Plan - Umpqua National
Forest. Final Environment Impact Statement: Appendices - Volume II. USDA
Forest Service, Pacifice Northwest Region. 315 pp.
USDA Forest Service and USD1 Bureau of Land Management. 1994. Record of
Decision for amendments to Forest Service and Bureau of Land Management
Planning Documents within the range of the northern spotted owl. Standards and
Guidelines for management of habitat for late successional and old-growth related
species within the range of the northern spotted owl. USDA Forest Service and
USD1 Bureau of Land Management. 74 pp.
40
Weikel, J. 1997. Habitat use by cavity-nesting birds in young thinned and unthinned
Douglas-fir forests of western Oregon. M.S. Thesis, Oregon State University,
Corvallis. 102 pp.
Winkler, H., D.A. Christie, and D. Nurney. 1995. Woodpeckers: An identification
guide to the woodpeckers of the world. Houghton Mifflin Co. New York, N.Y.
406 pp.
Wright, K.H. and G.M. Harvey. 1967. The deterioration of beetle-killed Douglas-fir in
Oregon and Washington. USDA Forest Service Research Paper. Pacific
Northwest Region, Portland, OR. 22 pp.
Zarnowitz, J.E. and D.A. Manuwal. 1985. The effects of forest management on cavitynesting birds in northwestern Washington. Journal of Wildlife Management 49:
255-263.
41
Habitat Associations of Woodpeckers at Multiple Scales in Managed Forests of the
Southern Oregon Cascades
CHAPTER 3
Habitat Associations of Woodpeckers at the Landscape Level in
Managed Forests of the Southern Oregon Cascades
INTRODUCTION
"The term 'patch' typically implies a discrete and internally homogeneous entity,
yet such patches are rarely observed in nature. Instead hierarchical mosaics of
patches within patches occur over a broad range of scales. Progress in
understanding how organisms respond to patchiness requires more realistic
conceptualizations that explicitly recognize these hierarchical layerings of patch
structure"
Wiens 1989
Wiens (1989) captured the crux of the dilemmas we face today in landscape
ecology and ecosystem management. There have been many recent studies investigating
processes and systems at large scales, with varying degrees of success. Researchers are
discovering that the study of systems at larger scales is a challenge, requiring that the
methodology and the very maimer in which we formulate questions be re-examined to
address problems at larger scales. Likewise, land managers are discovering that
management of ecosystems is a complex undertaking, and are floundering with few
previous examples from the past to use as guides.
Studies have shown that woodpeckers select sites for nesting based on
characteristics of individual trees that allow excavation of nest cavities (Madsen 1985,
Bull 1986c, Swallow and Gutierrez 1986, Schreiber 1987, Nelson 1989, Milne and Hejl
1989, Sedgwick and Knopf 1990, Chapter 2 this study). Selection for nest sites, however,
may begin at a broader scale, with woodpeckers selecting areas containing ample
opportunities for foraging and shelter. It has been proposed that habitat selection is
hierarchical in nature, with organisms choosing sites based on characteristics at multiple
levels (Block and Brennan 1993, Johnson 1980). Few studies that I am aware of have
42
examined habitat associations of woodpeckers beyond the nest tree or stand level. One
study examined associations between cavity-nesters and habitat features in Wyoming
bottomlands, (Gutzwiller and Anderson 1987) and found that cavity-nesters were
responding to characteristics at different spatial scales.
Because of the recent shift in forest management to look beyond the stand level
and plan for desired conditions over broader spatial and temporal scales to meet diverse
objectives, there is a need for information on habitat needs for nesting woodpeckers over
landscapes. The difficulty, however, in defining habitat suitablity increases markedly
when considering that selection is not based on one or two habitat characteristics, but
rather the combined effects produced by characteristics across different spatial scales that
elicit the observed species' response. In Chapter two, I presented the results of one part
of my study, examining the characteristics of nest trees of woodpeckers, and
characteristics of microsites immediately around the nest tree. In the second part of my
study, I expanded the scope of resolution to encompass the landscape context in which
the nests were located. I considered habitat features at the landscape scale that may be
influencing habitat selection by woodpeckers to determine whether associations existed
between habitat features and nest densities of woodpeckers.
My overall goals were two-fold; to determine whether habitat characteristics at
the landscape level were associated with woodpecker nest densities, and furthermore to
integrate the results of the study at the larger scale of resolution with the results of the
nest-level study to provide a more complete picture of habitat needs for nesting
woodpeckers.
OBJECTIVES
Specifically, my objectives were to:
•
Quantify selected habitat characteristics at the landscape level of resolution
•
Determine whether nest densities of northern flickers, hairy woodpeckers and red
-breasted sapsuckers were associated with measured habitat characteristics
43
STUDY AREA
The study was conducted in the Central Oregon Cascade Range, on the Diamond
Lake Ranger District of the Umpqua National Forest. Study sites are located
approximately 70 miles east of Roseburg, Oregon, in Douglas County between 47° 54'
and 47° 56' latitude (Fig. 1). Study sites were within the Umpqua National Forest on
sites varying in elevation from 1066 m-1463 m in the Umpqua High Cascade subprovince. The climate is characterized by moderate temperatures, wet, mild winters and
relatively cool, dry summers (Franklin and Dymess 1988). The region receives an
average of 152 cm of precipitation annually; of which 75-85% occurs between October
and April, primarily as rain, with snow at high elevations (Azet and McCrimmon 1990).
The study area is located within the western hemlock (Tsuga heterophylla) zone,
the most extensive vegetation zone found in the Pacific Northwest (Franklin and Dyrness
1988). In this zone western hemlock is considered the climax species, but this state is
rarely reached due to forest management activities (Harris 1984). The overstory is
typically dominated by Douglas-fir (Pseudotsuga menziesii), though white fir (Abies
concolor), western hemlock, mountain hemlock (Tsuga mertensiana), Pacific silver fir
(Abies amabilis), Pacific yew (Taxus
and Shasta red fir (Abies
commonly occur. Other species present include: incense-cedar (Calocedrus decurrens),
western redcedar (Thujaplicata), ponderosa pine (Pinusponderosa) and sugar pine
(Pinus lambertiana). Lodgepole pine (Pinus contorta) is found in sites located on the
eastern end of the study area. Understory vegetation varies depending on microsite
conditions, but generally is dominated by golden chinquapin (Castanopsis chrysophylla)4,
Sitka alder (Alnus sinuata), Pacific rhododendron (Rhododendron macrophyllum) vine
maple (Acer circinatum). Buckrush (Ceanothus integerrimus), and snowbrush
(Ceanothus velutinus) are found in young, regenerating stands. Ground cover is variable
and includes sword fern (Polystichum
vanillaleaf (Achlys triphylla),
bracken fern (Pteridium aquilinum),
44
Figure 6. Location of study sites for woodpecker habitat association
study on the Diamond Lake Ranger District, Umpqua National Forest
Southern Oregon Cascades.
STUDY SITE LOCATION
idy Sites
'Co's
0
kaomete.i
30
46
Cascade Oregon-grape (Berberis nervosa), huckleberries (Vaccinium spp.), salal
(Gaultheria shallon), and prince's pine (Chimophila umbellafa)
The study sites were dominated by mixed-conifer forest composed of at least
70%, but not more than 85% Douglas-fir trees. The remaining trees were a mixture of
western hemlock, mountain hemlock, true fir, and pine trees. Three sites had a small
component of lodgepole pine, not exceeding more than 5% of the total area. The sites
were at approximately the same elevation.
Volcanic activity has influenced landscape formation found in the study area,
depositing a layer of pumice across the landscape. Prior to European settlement in the
middle 19th century, the natural disturbance regime of the area was dominated by wild
fire events. Since its designation as National Forest land in 1905, the resource planning
strategy has emphasized efficient timber production, using even-aged management
methods. Due to management practices over the past 40 years, the condition of the
landscape is highly variable, consisting of a mosaic of habitat patches of varying age and
structure.
Five species of woodpeckers are known to breed within the study area; the blackbacked woodpecker, hairy woodpecker, northern flicker, pileated woodpecker, and red-
breasted sapsucker. Other species of woodpecker, including red-naped sapsuckers
(Sphyrapicus nuchalis) and white-headed woodpeckers (Picoides albolarvatus) are
residents on the east side of the Cascade Range, but occur only occasionally in the study
area.
METHODS
Study Site Selection
Eleven sites within the study area were selected for the study. Site selection
criteria were based on the proportion of the area comprised of mature forest, defined as
closed-canopy forest with> 40% canopy cover and trees averaging
53 cm in diameter.
The proportion of total forested area within study sites varied from 10% to 94%. The
remaining sites had intermediate amounts of forest, with the intent to select sites that
47
represented a continuum of amount of forest cover. Six sites were surveyed in 1995, and
seven in 1996; two of the sites sampled in 1995 were resampled in 1996.
Study sites chosen for woodpecker sampling were 200-ha in size. Home range
estimates of resident woodpeckers range from 12 ha for the red-breasted sapsucker to 200
ha for the pileated woodpecker (Bull 1977, Mannan et al. 1980, Brown et al. 1985,
Winider et a!. 1995). I chose 200-ha study sites because they were sufficiently large to
include multiple woodpecker home ranges, yet small enough to meet logistical
constraints.
Bird Sampling and Nest Searches
A 1600- x 1200-rn grid was established at each study site. Five transect lines
were located parallel to one another within each grid, with stations established every 200
meters along transect lines. Station points were used as references for recording
locations of nests.
I located woodpecker nests by walking along transect lines. Approximately every
200 meters I stopped to listen for woodpeckers. I attempted to visually locate each
woodpecker heard. Once located, I observed bird behavior, looking for evidence of a
nest. Indicators of nest presence included wood chips at the base of a tree, drumming
between pair members, territorial calling, and begging calls of nestlings. I followed
woodpeckers for as long as possible or until a nest was discovered. Woodpeckers were
not followed if they left the study site. Woodpeckers were easier to locate in opencanopy than in closed-canopy forest conditions, where they are more visible. I used the
relative amount of closed-canopy forest present in a transect to standardize search time.
To eliminate potential sampling biases, I allotted approximately twice the amount of time
to conduct searches in closed-canopy than I did in open-canopy forest.
All sites were visited a minimum of five times between 10 April and 14 July in
1995 and 1996, with 6 sites sampled in 1995 and 7 in 1996. Surveys were conducted
between 0500 and 1500. Potential nests were marked and later revisited to confirm
nesting status. Nests were considered to be confirmed when members of a pair were
48
observed excavating a cavity, exchanging incubation duties, or feeding fledglings at a
cavity entrance, or when fledglings were seen or heard in the cavity.
Creating a GIS Layer
Universal transverse mercator (UTM) coordinates for all nest trees were obtained
using a hand held GPS data logging system (Trimble Navigation©). I generated UTM
coordinates of each nest tree to the nearest 10 meters. Nest locations were downloaded to
a computer and correction factors from the U.S. Department of Defense-Portland base
were used to correct UTM coordinates. Corrected coordinates were brought into
AutoCAD (AutoCAD 1990). Maps of each study site were generated, integrating nest
locations, forest road systems, habitat patches, and site boundaries. The completed
coverages were imported into Arc/Info, a Geographical Information System (GIS)
software package that facilitates interactive analysis of spatial data (INFO 1994). All
patches within coverages were attributed with codes representing vegetation composition
and seral stage. I used definitions for seven different patch types to attribute individual
coverages (Table 7).
Statistical Analysis
FRAGSTATS-Background
I used FRAGSTATS (Marks and McGarigal 1995) to describe the structural
characteristics of the landscape. FRAGSTATS uses spatial coverages to calculate 50
metrices representing landscape and patch-type characteristics.
I analyzed images complete with landscape boundary and border. The boundary
defined the outside perimeter of the area and the border consisted of a 200-m buffer strip
surrounding the site. A border provides information about patches adjacent to the
landscape edge, and allows computation of meaningful edge metrices.
FRAGSTATS generates indices characterizing a specified area at the patch, class, and
landscape level. I focused my analysis at the class level and restricted the analysis to the
pre-defined target habitat patch type, mature, mixed-conifer forest. Class-level indices
described the characteristics of each patch type, or class within each study site.
49
Table 7. Patch type classification system used for FRAGSTATS analysis to classify
vegetation in 200-ha study sites. Mixed-conifer defined as forest composed of at least
70%. but not more than 85% Douglas-fir trees; with the remaining trees a mixture of
western/mountain hemlock, true fir, and pine trees. Lodgepole is defined as forest
composed of >80% lodgepole pine.
PATCH TYPE
DEFINITION
Mature mixed-conifer
> 90% mixed-conifer; average tree diameter> 53 cm,
canopy closure > 40%.
Mature lodgepole
> 90% lodgepole; average tree diameter > 38 cm, stand
density equal to or greater than 250 trees/ha.
Mixed-conifer pole
> 90% mixed-conifer; tree diameter between 10-28 cm,
stand density equal to or greater than 1000 trees/ha.
Mixed-conifer shelterwood
> 90% mixed-conifer; 30-45 trees/ha, snags present.
Mixed-conifer regeneration
with snags
> 90% mixed-conifer; average tree diameter < 10 cm,
Mixed-conifer regeneration,
shrub understory, with snags
> 90% mixed-conifer; average tree diameter < 10 cm,
open canopy with <40% canopy closure, > 60% shrub
open canopy with <40% canopy closure. <60% shrub
cover composed of Ceanothus spp, snags present.
cover composed of Ceanothus spp., snags present.
Mixed-conifer regeneration,
shrub understory, no snags
> 90% mixed-conifer; open canopy with <40% canopy
closure,> 60% shrub cover composed of Ceanothus spp.,
snags absent.
50
Class indices are useful when examining habitat fragmentation because they allow the
researcher to separate a landscape into distinct patches associated with unique habitat
characteristics (Marks and McGarigal 1995).
Class Level Analysis
A rank-correlation test performed on the data set indicated that several of the
descriptive variables were highly correlated (SAS Institute, Inc. 1990). In the case of
highly intercorrelated variables (p> 0.80), one of the variables was dropped from
analysis. FRAGSTATS generates indices that are redundant, expressing the same
information in a slightly different format. In cases where two indices measured the same
characteristic, but one was density-dependent, I included the density-dependent index in
the analysis. This allowed for comparisons between study sites. An attempt was made to
include variables that were relevant both biologically and within the context of the
questions asked. In some cases this decision was subjective, based upon interpretation of
the variables given my experience in the field. Through this process, several variables
were eliminated from the dataset, either because they were redundant, or because they
had no biological relevancy to the questions of interest.
The resultant set of 6 variables was modeled using multiple regression, to
determine whether measured characteristics at the landscape level were associated with
nest densities of red-breasted sapsuckers, northern flickers, or hairy woodpeckers (Table
8). Univariate analysis revealed that several of the variables were not normally
distributed. Where necessary, log transformations were used to normalize distributions.
To examine the association between landscape characteristics and nest abundance
for each woodpecker species, I used multiple regression (SAS Institute, Inc. SAS/STAT
1997). I used a forward stepwise procedure, setting the significance level at p < 0.05 for
entry into the model. I ran the analysis separately for each woodpecker species to
determine if differences could be detected.
51
Table 8. Definitions of class level habitat variables generated by FRAGSTATS to
describe landscape characteristics in 200-ha sites; Mixed-conifer defined as forest
composed of at least 70%, but not more than 85% Douglas-fir trees; with the remaining
trees a mixture of western/mountain hemlock, true fir, and pine trees. Edge contrast is
based on a weighting scheme to represent the degree of contrast between patch types,
based on McGarigal and McComb (1995) and Brooks (1997) (See Appendix C.).
FRAGSTATS
VARIABLE
Percent mature forest
DEFINITION
The proportion of area representing mature, mixed-conifer forest
with average tree diameter> 53 cm.
Patch density
Number of patches of mature, mixed-conifer forest per unit area.
Mean patch size
Average size in hectares of mature, mixed-conifer forest.
Edge density
The amount of edge habitat for mature, mixed-conifer forest per
unit area.
Area-weighted mean
edge-contrast index
Index that estimates the degree of contrast between a patch of
mature, mixed-conifer forest and its adjacent environment,
weighted by area of the patch.
Core area density
The density of core areas of mature, mixed-conifer forest within
landscape. Core areas are defined as patches large enough to
contain interior forest, with at least 100 meters from the core
center to an edge.
52
Edge Analysis
To assess relationships between nest-site location and habitat edges, I generated
159 random coordinates and plotted these random locations on each study site coverage.
I measured the distance from the random points and from each nest to the nearest habitat
edge, points that fell directly on an edge were assigned a value of zero. I did not include
the unfragmented site in this analysis as it did not posess edge habitat, and therefore was
not relevant to the question of interest.
For each species of woodpecker, I performed a Chi-square goodness-of-fit test to
determine whether woodpeckers disproportionately used trees along habitat edges for
nesting.
I also tested for differences in distances of nests and random locations to the
nearest habitat edge using a t-test. This was done for each species of woodpecker, for all
nests not located directly on an edge. Data were log-transformed for this analysis. The
statistical power of the t-test was calculated based on Cohen (1988).
RESULTS
FRAGSTATS Analysis of Landscape Indices
Results generated by FRAGSTATS analysis revealed several relationships
between nest density and habitat features. There was a significant negative trend between
the amount of mature forest and the density of woodpecker nests, suggesting that
woodpeckers select more open habitats for nesting. Regression analysis on
FRAGSTATS indices revealed slight differences among species.
Nest densities for red-breasted sapsuckers were negatively associated with mean
patch size of mature forest habitat (P < 0.036) (Fig. 7). Nests of northern flickers were
negatively associated with the proportion of mature forest in a landscape
(P <0.033) (Fig. 8). This association was also observed with the hairy woodpecker (P <
0.009) (Fig. 9). Regression did not detect any other variables among the habitat
characteristics calculated that were significant in explaining the variability in nest
densities between sites.
Figure 7. Association between the log of mean patch size and density of
red-breasted sapsucker nests over landscapes
10
Y=9.75 -
1.l4ln(x)
p<o.036
.
8
S
J)
6
S
S
S
S
4
2
.
0
I
0
1
I
I
I
2
3
4
Natural log of mean patch size (ha)
I
5
6
Figure 8. Association between proportion of mature forest
and density of northern flicker nests over landscapes
y = 9.57 - 0.077(x)
p < 0.033
S
10
S
rI)
z
'4S
E
z
.
5
.
S
0
S
I
0
20
40
I
60
Percent of Landscape in Mature Forest
i
80
a
I
100
Figure 9. Association between proportion of mature forest and density of
hairy woodpecker nests in landscapes
6
y=5.32 - 0.046(x)
.
5
p <0.0092
.
4
(,)
.
3
z
.
S
2
S
S
1
0
I
0
20
40
I
I
I
60
I
I
80
100
Percent of Landscape in Mature Forest
U'
U'
56
Edge Analysis
Placement of nests along habitat edges was significantly different between nests
of all woodpecker species and random points (Table 9). This association was highly
significant for red-breasted sapsuckers (X
2
= 34.12, df =
1,
P <5 x
1
Out of a 61
red-breasted sapsucker nests sampled, 23 occurred on habitat edges. Northern flickers
(X
2
= 8.23, df= 1, P <0.0041) and hairy woodpeckers(X
2
4.14, df=
1, P <0.042)
also nested in trees located along an edge more frequently than would be expected. Of
the 31 hairy woodpecker nests included in analysis, 4 were located along forest edges,
defined as the boundary between a patch of mature forest and regenerating stand, and one
was at the edge between a shelterwood and a regenerating stand.
Table 9. Location of nests of red-breasted sapsuckers, hairy woodpeckers and
northern flickers with respect to edge within landscapes. Edge was defined
as representing a distinct boundary between a stand of mature forest
and a regenerating stand, or as the boundary between a shelterwood and a
regenerating stand.
OBSERVED
On Edge
Not on Edge
Red-breasted Sapsucker
23
38
Northern flicker
12
51
5
26
10
149
Hairy woodpecker
Random
57
Comparisons using t-tests
T-tests performed on nests not located directly on an edge did not indicate a
significant difference between nest tree placement and random locations in proximity to
edge (Table 12). The statistical power of the t-test was high (>0.99 to detect a difference
between nest sites and random sites). Therefore I am confident that the conclusion can be
made that once nests located directly on habitat edges are accounted for, there is no
difference in distance to an edge between nest trees and random trees.
Table 10. Comparison of distance from an edge between woodpecker nests and random
locations, after all points located directly on an edge were removed. Distances were logtransformed for analysis, but non-transformed values for means and standard deviations
are presented here.
n
X
StdDev
P<{t)
(meters)
Random
149
63.4
2.43
Hairy
woodpecker
24
75.9
2.75
0.3655
Northern
flicker
50
69.4
2.54
0.5583
Red-breasted
sapsucker
38
54.6
2.54
0.4323
58
DISCUSSION
Nest densities of woodpeckers were associated with habitat variation within
landscapes. Woodpecker nest-site selection appears to be influenced by overall landscape
pattern and location with respect to edges.
Northern flickers and hairy woodpeckers exhibited negative associations with the
proportion of mature, mixed-conifer forest. This is consistent with results of similar
studies of woodpeckers throughout the Pacific Northwest that have found greater
abundances of woodpecker nests in openings and open-canopy forests(Hagar 1960,
Madsen 1985, Hagar et al. 1996, Weikel 1997). Hairy woodpeckers and northern flickers
will nest in young regenerating forests, if adequate numbers of snags are present (Hagar
1960, Bull 1980, Mannan et al. 1980, Raphael and White 1984, Schreiber and deCalesta
1992). Madsen (1985) reported that woodpecker nest-sites had significantly less canopy
cover than randomly located sites in the southern cascades of Washington. Additionally,
some cavity-nesters in the Oregon Coast Range respond positively to thinning (Hagar et
al. 1996, Weikel 1997). Hagar et al. (1996) attributed this behavioral response to the
enhancement of foraging habitat created by the residual slash and trees left behind after
harvest activities, but Weikel (1997) questioned this conclusion.
Species-specific patterns
I detected statistically significant associations with one habitat component and
nest-site location for northern flickers at the landscape level. Densities of northern flicker
nests decreased as the amount of mixed-conifer forest increased within a landscape. This
species has been described as a habitat generalist, and is often found nesting in forest
openings (Hagar 1960, Bent 1964, Raphael and White 1984, Nelson 1989, Lundquist and
Mariani 1991). Raphael and White (1984) reported that northern flickers nest in a wide
variety of habitats in northern California, primarily in burned areas and
lodgepole/meadow conditions. Hagar (1960) found that densities of northern flickers
increased in response to logging, provided that ample snags for nesting and foraging were
left following harvest. The diet of the northern flicker consists primarily of ants
(Hymenoptera), but is supplemented by termites (Isoptera), caterpillars (Lepidoptera),
59
beetles and beetle larvae (Coleoptera), crickets (Orthoptera), aphids (Homoptera) spiders
(Araneida) and berries (Beal 1911, Winkler et al. 1995). Northern flickers were observed
foraging in regenerating stands, often with little ground cover, where preferred forage
was available. The foraging habits of the northern flicker may partially explain their
affinity for open-canopy forest.
Northern flickers are weak excavators, and use soft, well-decayed snags for
excavating nest cavities (Raphael and White 1984, Lundquist and Mariani 1991, Winkler
et al. 1995, this study). Well-decayed, soft snags suitable for excavation by northern
flickers are often found in regenerating stands and forest openings, where exposure to the
wind and weather accelerates the rate of decay (Cline et al. 1980).
Density of red-breasted sapsucker nests was negatively associated with the size of
mature forest patches throughout a landscape. Though this statistic is related to the
overall amount of mature forest, it relates more closely to distribution of that patch type
across the landscape. Spatial structure of habitat patches over a landscape may have an
effect on species' distribution, influencing the amount of edge, amount of interior forest,
and the availability of required resources. Red-breasted sapsuckers have been described
as forest specialists (Raphael and White 1984), whereas other studies have associated
them with older forests (Nelson 1989, Lundquist and Mariani 1991). I often observed
red-breasted sapsuckers foraging in stands of mature forest, where they foraged mainly on
hemlock and yew trees. Sapsuckers that had nested in a regenerating stand were seen
making frequent forays to adjacent forested stands when feeding nestlings. Relatively
little is known about the foraging habits of the red-breasted sapsucker. They feed
primarily on sap, as do other members of Sphyrapicus, but it is thought that ants may be
an important food source for nestlings (Winkler et al. 1995). Dietary needs may be
specialized enough to restrict sapsuckers to certain habitat types for foraging. The
negative association with mature forest patch size may be due in part to the sapsucker's
need for diverse patch types within their home range to meet habitat requirements. It may
be advantageous for sapsuckers to nest in trees that offer access to several different patch
types.
60
Density of hairy woodpecker nests were positively associated with open canopy
forest with snags present, and negatively associated with the amount of mature forest in
landscapes. This observation is consistent with those of other studies. Hagar et at.
(1996) and Weikel (1997) both reported positive responses of hairy woodpeckers to
thinning in forests of the Oregon Coast Range. Weikel also detected more hairy
woodpeckers in heavily thinned stands than in moderately thinned stands. She
hypothesized that this was due to increased abundance of prey in thinned stands. The diet
of the hairy woodpecker consists mainly of species from the order Coleoptera;
supplemented by those in Hymenoptera, Orthoptera, Araneida, and Diptera (Otvos and
Stark 1965, Winkler et at. 1995). However, hairy woodpeckers are quite versatile and
will supplement their diet with seeds and fruit (Bent 1964). This versatility may allow
them to take advantage of foraging opportunities available in different stand types.
Weikel (1997) reported that hairy woodpeckers foraged heavily on large, well-decayed
snags and logs. This suggests that the presence of large dead wood is an important
habitat attribute for hairy woodpeckers, and may be a stronger driving force in habitat
selection than stand type or seral stage.
Edge Effect
Woodpeckers chose trees along edge habitatsmore frequently than would be
expected due to chance alone This affinity for edge habitat by woodpeckers has been
described by others (McGarigal and McComb 1995). For red-breasted sapsuckers, the
association with edge habitat was very strong, roughly one-third of all red-breasted
sapsucker nests were located on a habitat edge.
Aldo Leopold, one of the first wildlife biologists to recognize the importance of
edge habitat for wildlife, stated that edge habitat is desirable because it "offers
simultaneous access to more than one environmental type, or the greater richness of
border vegetation, or both" (Leopold 1933). Hunter (1990) defined edges as transition
zones between two habitat patches with a high degree of contrast in vegetative and/or
structural characteristics. Unique conditions found in edges create suitable habitat for a
variety of plants and animals (Chen et at. 1993). Helle and Muona (1985) reported that
61
several types of invertebrates were relatively more abundant near forest-clearcut edges. I
hypothesize that edge habitats support higher densities of insects, providing enhanced
foraging opportunities for woodpeckers. Conditions found along edges also may promote
fungal growth on trees that accelerate tree decay and encourage the invasion of
woodpecker prey species. It probably is not due to one single factor but the combination
and integration of several factors that make edges preferred locations for nesting by these
three woodpecker species.
While it is true that edge habitats support a greater diversity of wildlife species,
they can also be inhospitable to some species. Edges may be detrimental to species who
are considered interior forest-dwellers. Studies, primarily conducted in the eastern
United States, have shown increased rates of nest predation on songbirds nesting near
edges than for those nesting in forest interior (Hunter 1990). When developing long-term
management plans, careful consideration should be given to overall landscape diversity
with respect to edges. The goal of enhancing wildlife diversity by the creation of edges
through management activities must be balanced with the need to maintain the integrity
of the forest matrix for forest-dwelling species.
CONCLUSIONS
Nesting habitat for woodpeckers can be provided within managed landscapes as
long as adequate numbers of suitable nest snags are made available. In some cases, the
enhancement of foraging opportunities created by forest openings may allow
woodpeckers to nest at higher densities in areas with little overstory canopy, once again
provided that appropriate numbers of suitable snags are retained for nesting.
Woodpeckers exhibited a positive association to increased landscape diversity.
Results of landscape analysis revealed that woodpeckers nested at higher densities in
areas characterized by greater habitat complexity. The results of this study suggest that
habitat complexity, specifically with regard to patch heterogeneity and the presence of
edge habitat, may be important factors in nest-site selection for woodpeckers.
62
L1TERAT(JRE CITED
Azet, 1. L.A. McCrimmon. 1990. Preliminary Plant Association of the Southern
Oregon Cascade Mountain Province. USDA Forest Service Publication. Siskiyou
National Forest. 113 pp.
Autodesk, Inc. 1990. AutoCAD Release 11: Reference manual, publication AC1 1RM.
640 pp.
Beal, F.E.L. 1911. Food of the woodpeckers of the United States. Biological Survey
Bulletinv. 37.
Bent, A.C. 1964. Life Histories of North American woodpeckers. Dover Publications.
New York, N.Y. 334 pp.
Block and Brennan. 1993. The habitat concept in ornithology: Theory and applications.
D.M. Power, ed. Current ornithology, Volume 11. Plenum
Pages 35-83
Press. New York, N.Y.
Brooks, J.P. 1997. Bird-habitat relationships at multiple spatial resolutions in the
Oregon Coast Range. M.S. Thesis, Oregon State University, Corvaffis. 46 pp.
Brown, E.R. tech. ed. 1985. Management of wildlife and fish habitats in forests of
western Oregon and Washington. Part 2 Appendices. USDA Forest Service,
General Technical Report PNW-R8-F&WL-192-1985. Portland, OR. 302 pp.
Bull, E.L. 1977. Habitat utilization of the pileated woodpecker, Blue Mountains,
Oregon. M. S. Thesis. Oregon State University, Corvallis. 58 pp.
Bull, E.L. 1980. Resource partitioning among woodpeckers in northeastern Oregon
Ph.D. Thesis. University of Idaho, Moscow. 109 pp.
Bull, E.L., S. R. Peterson, J.W. Thomas. 1986c. Resource partitioning among
woodpeckers in northeastern Oregon. USDA Forest Service Research Note,
PNW-444. 19 pp.
Chen, J., J.F. Franklin, and T.A. Spies. 1993. Contrasting microcimates among clearcut,
edge, and interior of old-growth Douglas-fir forest. Agricultural and Forest
Meteorology 63: 219-237.
63
Cline, S.P., A.B. Berg, and H.M. Wight. 1980. Snag characteristics and dynamics in
Douglas-fir forests, western Oregon. Journal of Wildlife Management. 44: 773786.
Cohen, J. 1988. Statistical power analysis for the behavioral sciences. Second edition.
Lawrence Eribaum Associations, Inc. Hillsdale, N.J.
Franidin, J.F., C.T. Dryness. 1988. Natural vegetation of Oregon and Washington.
Oregon State University Press, Corvallis. 452 pp.
Gutzwiller, K.J., and S.H. Anderson. 1987. Multiscale associations between cavitynesting birds and features of Wyoming streamside woodlands. Condor 89: 534548.
Hagar, D. C. 1960. The interrelationships of logging, birds and timber regeneration in
the Douglas-fir region of northwest California. Ecology 41: 116-125.
Hagar, J.C., W.C. McComb, and W.H. Emmingham. 1996. Bird communities in
commercially thinned and unthinned Douglas-fir stands of western Oregon.
Wildlife Society Bulletin 24: 353-366.
Harris, L.D. 1984. The fragmented forest. University of Chicago Press, Chicago,
I.L. 2llpp.
Helle P., and J. Muona. 1985. Invertebrate numbers in edges between clear-fellings and
mature forests in northern Finland. Silva Fenn. 19: 28 1-294. Found In: Hunter,
Malcom. 1990. Wildlife, forests and forestry: Principles of managing forests for
biological diversity. Prentice-Hall, Inc. Englewood Cliffs, N.J. 370 pp.
Hunter, M.L. Jr. 1990. Wildlife, forests and forestry: Principles of managing
forests for biological diversity. Prentice-Hall, Englewood Cliffs, N.J. 370 pp.
INFO. Arc/Info Version 7. 1994. Environmental Systems Research Institute, Inc.
Redlands, C.A. 337 pp.
Johnson, D.H. 1980. The comparison of usage and availability measurements for
evaluating resource preference. Ecology 61: 65-70.
Leopold, A. 1933. Game Management. Charles Scribner Sons. New York, N.Y. 481 pp.
Lundquist R.W. and J.M. Mariani. 1991. Nesting habitat and abundance of snagdependent birds in the southern Washington Cascade Range. Pages 22 1-239 L.
F. Ruggiero, K.B. Aubry, A.B. Carey, and M.H. Huff, technical coordinators.,
Wildlife and vegetation of unmanaged Douglas-fir forests. USDA Forest Service
General Technical Report PNW-GTR-285.
______
64
Madsen, S.J. 1985. Habitat use by cavity-nesting birds in theOkanogan National Forest,
Washington. M.S. Thesis. University of Washington, Seattle. 113 pp.
Mannan, R.W., E.C. Meslow, H.M. Wight. 1980. Use of snags by birds in
Douglas-fir forests, western Oregon. Journal of Wildlife Management. 44: 787797.
Marks, B. and K. McGarigal. 1995. Fragstats: Spatial pattern analysis program for
quantifying landscape structure. USDA Forest Service General Technical Report,
PNW-GTR-351. 122 pp.
McGarigal, K. and W.C. McComb. 1995. Relations between landscape structure and
breeding birds in the Oregon Coast Range. Ecological Monographs. No. 65: 235260.
Mime, K.A., and S.J. Heji. 1989. Nest-site characteristics of white-headed woodpeckers.
1989. Journal of Wildlife Management 53: 50-54.
Nelson, S.K. 1989. Habitat use and densities of cavity-nesting birds in the Oregon
Coast Ranges. M.S. Thesis. Oregon State University, Corvallis. 157 pp.
Otvos, I.S. and R.W. Stark. 1985. Arthropod food of some forest-inhabiting birds. The
Cannadian Entomologist 117:971-990
Raphael, M.G. and M. White. 1984. Use of snags by cavity-nesting birds in the Sierra
Nevada. Wildlife Monograph No. 86. 66 pp.
1990.
SAS/S TAT Procedures Guide, Version 6, Third Edition, Cary,
N.C: 705 pp.
SAS/STAT software: changes and enhancements through release 6.12.
Cary,N.C. :1167 pp.
1997.
Schreiber, B. 1987. Bird use of snags on clearcuts in central coastal Oregon. M.S.
Thesis, Oregon State University, Corvallis. 63 pp.
Schreiber, B. and D.S. deCalesta. 1992. The relationship between cavity-nesting birds
and snags on clearcuts in wetern Oregon. Forest Ecology and Management 50:
299-3 16.
Sedgwick, J.A., and F.L. Knopf. 1990. Habitat relationships and nest site characteristics
of cavity-nesting birds in cottonwood floodplains. Journal of Wildlife
Management 54: 112-124.
65
Swallow, S.K. and R.J. Gutierrez. 1986. Primary cavity-site selection by birds. Journal
of Wildlife Management 50: 576-583.
USDA Forest Service and USD1 Bureau of Land Management. 1994. Record of
Decision for amendments to Forest Service and Bureau of Land Management
Planning Documents within the range of the northern spotted owl. Standards and
Guidelines for management of habitat for late successional and old-growth related
species within the range of the northern spotted owl. USDA Forest Service and
USD1 Bureau of Land Management. 74 pp.
Weikel, J. 1997. Habitat use by cavity-nesting birds in young thinned and unthinned
Douglas-fir forests of western Oregon. M.S. Thesis, Oregon State University,
Corvallis. 102 pp.
Wiens, J.A. 1989. Spatial Scaling in Ecology. Functional Ecology 3: 385-397.
Winkler. H., D.A. Christie, and D. Nurney. 1995. Woodpeckers: An identification
guide to the woodpeckers of the world. Houghton Mifflin Co. New York, N.Y.
406 pp.
66
Habitat Associations of Woodpeckers at Multiple Scales in Managed Forests of the
Southern Oregon Cascades
CHAPTER FOUR
Conclusions and Implications for Management for Woodpeckers in the
Oregon Cascades
Associations between woodpeckers and habitat characteristics occurred at more
than one spatial scale, and observations made at one scale were not always detected at
another. Two important conclusions can be drawn from these results. First, it is
imperative that spatial scale is considered in wildlife-habitat association studies. If scale is
disregarded, associations may go undetected, and in some cases, results may be incorrectly
interpreted. Second, management plans designed to provide and maintain suitable habitat
for woodpeckers must consider the larger landscape context in which they are found. It is
important to retain adequate numbers of suitable nesting snags but consideration also
should be given to snag placement over landscapes.
LARGE DIAMETER SNAGS
Current guidelines for snag management outlined in the Northwest Forest Plan
(NFP) set minimal requirements for retention of snag habitat. These guidelines are based
on nesting habitat needs of the pileated woodpecker, and require that a sufficient number
of snags be retained to support 40% of the potential populations level for pileated
woodpeckers. The plan recommends that snag management occur within areas of green
tree retention, and that green trees can be left as 'snag recruitment' trees if snag density is
not adequate (USDA-Forest Service and USD1-Bureau of Land Management 1994). The
Umpqua National Forest Land and Resource Management Plan (USDA Forest Service
1990) requires that 5 trees/ha greater than 30 cm in diameter and 0.8 trees/ha greater than
50 cm in diameter be retained, and that 15 green trees/ha be left to provide future snags.
67
When snag densities are insufficient, guidelines call for the recruitment of snags
by artificial means. Guidelines require that snags be maintained that are 35 cm or greater
in dbh. I found woodpeckers nesting in trees substantially larger than 35 cm; average
diameter for woodpecker nest trees varied from 78 cm (northern flicker) to 81 cm (red-
breasted sapsucker). My results, supported by numerous other studies throughout the
Pacific Northwest, indicate that woodpeckers use larger diameter trees for nesting
(Mannan et al. 1980, Raphael and White 1984, Madsen 1985, Nelson 1989, Lundquist
and Mariani 1991, this study). There is evidence that large diameter snags provide
foraging habitat in addition to nesting habitat for woodpeckers. Weikel (1997) reported
that large diameter well-decayed snags were an important foraging habitat component for
hairy woodpeckers and other cavity-nesters in the Oregon Coast Range.
Providing large snags will help meet many wildlife objectives, and will aid in the
overall maintenance of healthy forest ecosystems. For example, flying squirrels and
long-legged myotis (Myotis volans) use large diameter snags for roosting (Feen 1997,
Ormsbee 1996). Over time, snags decay and are recruited to the stand as down woody
material, functioning as an important foraging substrate for many species of cavitynesters (Weikel 1997) and creating travel corridors for small mammals such as the redbacked vole (Thompson 1996).
Based on my results, I recommend that snags 80 cm or greater be retained
following harvest to provide nesting habitat for woodpeckers. This number represents the
average diameter of nest tree used by all three species of woodpeckers. Providing snags
equal to or greater than the average size reported is preferable to leaving snags that meet
only the minimal requirements, and will provide more suitable habitat over the long run.
EDGE
Edge had a dramatic effect on density and distribution of woodpecker nests in my
study area. Although an association with edge has been described for several taxa by
other researchers (MacGarigal and McComb 1995), to my knowledge no other study has
documented the importance of edge habitat for woodpeckers. Of 163 total nests, 40 were
located directly on an edge. The mechanism driving this association remains unclear.
68
The importance of edge for some species has long been recognized, particularly
for big game species such as deer and elk (Hunter 1990). Recently, the term 'edge effect'
has come into use to describe the overall increase in wildlife species richness along
edges. For some species, especially those that require interior forest for nesting and
foraging, edges can be detrimental. Reports of large declines in songbird populations in
the eastern United States have been attributed to increased rates of nest parasitism along
habitat edges (Hunter 1990). Fragmentation resulting from logging has increased the
amount of edge in forest lands. Consideration must be given to the development and
adoption of a management strategy that provides some edge habitat to promote wildlife
diversity, while minimizing the detrimental effects that occur when too much edge is
created. At the landscape level, it may be important to provide habitat that represents a
diversity of patch types for nesting woodpeckers.
Based on the results of my research, I suggest implementing a plan that
incorporates the use of alternative regeneration techniques over a broad landscape, such
as partial cut and shelterwood prescriptions. Prescriptions could be used to treat small
20-3 0 acre patches over a landscape to create habitat diversity while maintaining the
integrity of the forest matrix--in effect emulating natural forest openings resulting from
tree mortality, blow down events, or low-intensity wildfires. Because my results indicate
that woodpecker nest density increases with overall habitat complexity, using harvest
strategies that create complexity would meet the goals of providing timber resources
while at the same time enhancing habitat for woodpeckers.
NATURAL AGENTS OF DIVERSITY
In attempting to provide suitable habitat for woodpeckers in other areas, regional
conditions need to be considered, to tailor management plans to meet the needs of
resident cavity-nesters. Lundquist and Mariani (1991) reported that woodpeckers in the
southern Washington Cascades disproportionately used western white pine trees for
nesting. These results may be driven more by unique site conditions of the region than by
any other factor. In my study area, white fir snags were found at high densities in small
pockets of forest infected by a root rot disease, armallaria (Armallaria obscura). Stands
69
infected with the disease provide an abundance of snags that serve as nesting and
foraging substrate for woodpeckers. These snags eventually fall and are recruited to the
stand as part of the down wood component, continuing to serve as foraging substrate for
woodpeckers. Viewed from a landscape perspective, there are two concerns that need to
be considered. The first is provision of long-term nesting and foraging habitat for
woodpeckers. The second concern is a silvicultural objective, to minimize the loss of
timber due to disease, and also minimize the rate of spread to uninfected stands. Van der
Kamp (1991) suggested taking a different approach to management of pathogens
including armallaria, in ecosystems. He asserted that root diseases can be influential in
creating unique habitats which favor plant and animal species not well-suited for living in
dense, even-aged, coniferous forests, and that pathogens are agents of diversity that can
be utilized to create desired habitat conditions. If small pockets of armallaria root rot are
allowed to persist within the landscape, spreading at an average rate of 1 meter annually
(Goheen et a!. 1994), they will provide a continous supply of nesting habitat for
woodpeckers. To minimize spread of disease, adjacent stands can be planted with
resistant tree species, thus acting as a natural barrier to further spreading and maintaining
a localized patch of infected trees. Forest gaps created by tree death will add to overall
habitat complexity, which will also benefit woodpecker populations. These ideas can be
incorporated into effective management plans to provide suitable nesting habitat for
woodpeckers over landscapes. Wildlife objectives and timber production can both be
achieved if a scheme is used that balances forest diversity, overall forest health, and
commercial productivity.
RESEARCH RECOMMENDATIONS
Because I did not measure the reproductive fitness of nesting woodpeckers, I can
make oniy limited inferences about habitat suitability. Species abundance does not
necessarily equate to suitable habitat (Van Home 1983). Further study needs to be done
to measure reproductive fitness of individual woodpecker species in response to forest
70
management activities. Studies that examine nest success of woodpeckers in different
habitat patch types over landscapes will provide information on habitat suitability.
Furthermore, I examined habitat associations of nesting woodpeckers, and did not
attempt to
foraging behavior of woodpeckers. Very little information exists on
foraging needs of woodpeckers, much emphasis has been placed instead upon nesting
habitat needs of woodpeckers. To develop management plans that provide both nesting
and foraging habitat components, more information is needed on foraging resource
requirements of individual woodpecker species.
The observed importance of edge requires further examination. Currently, the
mechanism responsible for this association remain unclear. Though I hypothesize that this
response is the result of enhanced foraging opportunities near edge, further research is
needed to test this. Specifically, insect population density along edges needs to be
determined, and compared with populations in adjacent stands. Studies that examine the
interrelationship between woodpeckers and food resources may provide answers to
explain this phenomena, and will be beneficial in creating suitable plans for management of
woodpeckers.
LITERATURE CiTED
Feen, J.S. 1997. Winter den sites of northern flying squirrels in Douglas-fir forests of
the south central Oregon Cascades. M.S. thesis. Oregon State University,
Corvallis. 45 pp.
Goheen, E.M., D.J. Goheen, and K. Marshall. 1994. Insect and disease assessment of the
demonstration of ecosystem management options site: Diamond Lake Ranger
District, Umpqua National Forest. Southwest Oregon Forest Insect and Disease
Technical Center publication. 17 pp.
Hunter, M.L. Jr. 1990. Wildlife, forests and forestry: Principles of managing
forests for biological diversity. Prentice-Hall, Englewood Cliffs, N.J. 370 pp.
71
Lundquist R.W. and J.M. Mariani. 1991. Nesting habitat and abundance of snagdependent birds in the southern Washington Cascade Range. Pages 22 1-239 L.
F. Ruggiero, K.B. Aubry, A.B. Carey, and M.H. Huff, technical coordinators.,
Wildlife and vegetation of unmanaged Douglas-fir forests. USDA Forest Service
General Technical Report PNW-GTR-285.
Madsen, S.J. 1985. Habitat use by cavity-nesting birds in the Okanogan National Forest,
Washington. M.S. Thesis. University of Washington, Seattle. 113 pp.
Mannan, R.W., E.C. Meslow, H.M. Wight. 1980. Use of snags by birds in
Douglas-fir forests, western Oregon. Journal of Wildlife Management 44: 787797.
McGarigal, K. 1993. Relationship between landscape structure and avian abundance
patterns in the Oregon Coast Range. Ph.D. Dissertation. Oregon State
University, Corvallis. 273 pp.
Nelson, S.K. 1989. Habitat use and densities of cavity-nesting birds in the Oregon
Coast Ranges. M.S. Thesis. Oregon State University, Corvallis. 157 pp.
Ormsbee, P. 1996. Selection of day roosts by female long-legged myotis (Myotis
volans) in forests of the central Oregon Cascades. M.S. Thesis. Oregon State
University, Corvallis. 63 pp.
Raphael, M.G. and M. White. 1984. Use of snags by cavity-nesting birds in the Sierra
Nevada. Wildlife Monograph No. 86. 66 pp.
Thompson, R.L. 1997. Home range and habitat use of western red-backed voles in
mature coniferous forests in the southern Oregon Cascades. M.S. thesis. Oregon
State University, Corvallis. pp.
USDA Forest Service. 1990. Land and Resource Management Plan - Umpqua National
Forest. Final Environment Impact Statement: Appendices - Volume II. USDA
Forest Service, Pacific Northwest Region. 315 pp.
USDA Forest Service and USD1 Bureau of Land Management. 1994. Record of
Decision for amendments to Forest Service and Bureau of Land Management
Planning Documents within the range of the northern spotted owl. Standards and
Guidelines for management of habitat for late successional and old-growth related
species within the range of the northern spotted owl. USDA Forest Service and
USD1 Bureau of Land Management. 74 pp.
Van Home, B. 1983. Density as a misleading indicator of habitat quality. Journal of
Wildlife Management 47:893-901.
72
Van der Kamp, B.J. 1991. Pathogens as agents of diversity in forest landscapes. The
Forestry Chronicle 67: 353-354.
Weikel, J. 1997. Habitat use by cavity-nesting birds in young thinned and unthinned
Douglas-fir forests of western Oregon. M.S. Thesis, Oregon State University,
Corvallis. 102 pp.
73
BIBLIOGRAPHY
Autodesk, Inc. 1990. AutoCAD Release 11: Reference manual, publication AC! 1RM.
640 pp.
Azet, T., and L.A. McCrimmon. 1990. Preliminary Plant Association of the Southern
Oregon Cascade Mountain Province. USDA Forest Service Publication. Siskiyou
National Forest. 113 pp.
Balda, R.P. 1975. The relationships of secondary cavity-nesters to snag densities in
western coniferous forests. USDA Forest Service Wildlife Technical
Bulletin 1, Albuquerque, N.M. 37 pp.
Beal, F.E.L. 191!. Food of the woodpeckers of the United States. Biological Survey
Bulletinv. 37.
Beebe, S.B. 1974. Relationships between insectivorous hole-nesting birds and forest
management. Yale University School of Forestry and Environmental Studies.
49 pp.
Bent, A.C. 1964. Life Histories of North American woodpeckers. Dover Publications.
New York, N.Y. 334 pp.
Block, W.M., and L.A. Brennan. 1993. The habitat concept in ornithology: Theory
D.M. Power, ed. Current ornithology, Volume 11.
applications. Pages 35-83
Plenum Press. New York, N.Y.
Brooks, J.P. 1997. Bird-habitat relationships at multiple spatial resolutions in the
Oregon Coast Range. M.S. Thesis, Oregon State University, Corvallis. 46 pp.
Brown, E.R. tech. ed. 1985. Management of wildlife and fish habitats in forests of
western Oregon and Washington. Part 2 Appendices. USDA Forest Service,
General Technical Report PNW-R8-F&WL-192-1985. Portland, OR. 302 pp.
Bull, E.L. 1977. Habitat utilization of the pileated woodpecker, Blue Mountains,
Oregon. M. S. Thesis. Oregon State University, Corvallis. 58 pp.
Bull, E.L. 1980. Resource partitioning among woodpeckers in northeastern Oregon
Ph.D. Dissertation. University of Idaho, Moscow. 109 pp.
Bull, E.L. 1986a. Ecological value of dead trees to cavity-nesting birds in northeastern
Oregon. Oregon Birds 12: 9 1-99.
74
Bull, E.L. I 986b. Methods of killing trees for use by cavity-nesters. Wildlife
Society Bulletin 14:142-146.
Bull, E.L., S.R. Peterson, and J.W. Thomas. 1 986c. Resource partitioning among
woodpeckers in northeastern Oregon. USDA Forest Service Research Note,
PNW-444. 19 pp.
Bunnell, F.L., L.L. Kremsater, and R.W. Wells. 1997. Likely consequences of forest
management on terrestrial, forest-dwelling vertebrates in Oregon. Report M-7 of
the Centre for Applied Conservation Biology, University of British Columbia.
129 pp.
Capra, F. 1982. The turning point: science, society and the rising culture.
Bantam. New York, N.Y. 464 pp.
Chambers, C.L., T. Carrigan, T.E. Sabin, J.Tappeiner, and W.C. McComb. 1997. Use of
artificially created Douglas-fir snags by cavity-nesting birds. Western Journal of
Applied Forestry 12:93-97.
Chen, J., J.F. Franklin, and T.A. Spies. 1993. Contrasting microclimates among clearcut,
edge, and interior of old-growth Douglas-fir forest. Agricultural and Forest
Meteorology 63: 219-237.
Cline, S.P. 1977. The characteristics and dynamics of snags in Douglas-fir forests of the
Oregon Coast Range. M.S. thesis. Oregon State University, Corvallis. 107 pp.
Cline, S.P., A.B. Berg, and H.M. Wight. 1980. Snag characteristics and dynamics in
Douglas-fir forests, western Oregon. Journal of Wildlife Management 44: 773786.
Cohen, J. 1988. Statistical power analysis for the behavioral sciences. Second edition.
Lawrence Erlbaum Associations, Inc. Hilisdale, N.J.
Conner, R.N., O.K. Miller, and C.S. Adkisson. 1976. Woodpecker dependence on trees
infected by fungal heart rots. Wilson Bulletin 88: 575-58 1.
Conner, R.N. 1979. Seasonal changes in woodpecker foraging methods: strategies for
winter survival. Pages 95-105 In: J.G. Dickson, R.N. Conner, R.R. Fleet, eds.
The role of insectivorous birds in forest ecosystems: Proc. of a symposium.
Nacogdoches,Texas. Academic Press, Inc. New York, N.Y.
den Boer, P.J. 1981. On the survival of populations in a heterogeneous and variable
environment. Oecologia 50: 39-53.
75
Edgerton, P.J., and J.W. Thomas. 1977. Silvicultural options and habitat values in
coniferous forests. Paper presented at the Nongame Bird Habitat Management in
Coniferous Forests of the Western United States, Portland, Oregon. Feb. 7-9,
1977. pp. 56-65.
Evans, K., and R.N. Conner. 1979. Snag management. pages 214-225 III: R.M. DeGraaf
eds. Management of north central and northeastern forests for
and K.E.
nongame birds. USDA Forest Service General Technical Report NC-5 1, St. Paul,
M.N.
Feen, J.S. 1997. Winter den sites of northern flying squirrels in Douglas-fir forests of
the south central Oregon Cascades. M.S. thesis. Oregon State University,
Corvallis. 45 pp.
Filip, G. Personal Communication. October 15, 1995. Forest pathology expert. Oregon
State University, Corvallis.
Forman, R.T., and M. Godron. 1981. Patches and structural components for a
landscape ecology. Bioscience 31: 733-740.
Forman, R.T., and M. Godron. 1986. Landscape ecology. John Wiley and Sons, New
York,N.Y. 619 pp.
Franklin, J.F., and R.T. Forman. 1987. Creating landscape patterns by forest
cutting: ecological consequences and principles. Landscape Ecology 1: 5-18
Franklin, J.F., and C.T. Dryness. 1988. Natural vegetation of Oregon and Washington.
Oregon State University Press, Corvallis. 452 pp.
Franzreb, K.E., and R.D. Ohmart. 1978. The effects of timber harvesting on
breeding birds in a mixed coniferous forest. Condor 80: 43 1-441.
Garrison, G.A. 1949. Uses and modifications for moosehorn crown closure estimation.
Journal of Forestry 47: 733-735.
Goheen, E.M., D.J. Goheen, and K. Marshall. 1994. Insect and disease assessment of the
demonstration of ecosystem management options site: Diamond Lake Ranger
District, Umpqua National Forest. Southwest Oregon Forest Insect and Disease
Technical Center publication. 17 pp.
Graves, K. 1995. Personal Commnication. March 15, 1997. USDA Forest Service
Natural Resource Manager, Diamond Lake Ranger District, Umpqua National
Forest.
76
Gutzwiller, K.J., and S.H. Anderson. 1987. Multiscale associations between cavitynesting birds and features of Wyoming streamside woodlands. Condor 89: 534548.
Haapanen, A. 1965. Bird fauna of the finnish forests in relation to forest succession. I.
Am. Zool. Fenn. 2:153-196
Hagar, D.C. 1960. The interrelationships of logging, birds and timber regeneration in
the Douglas-fir region of northwest California. Ecology 41: 116-125.
Hagar, J.C., W.C. McComb, and W.H. Emmingham. 1996. Bird communities in
commercially thinned and unthinned Douglas-fir stands of western Oregon.
Wildlife Society Bulletin 24: 353-366.
Harris, L.D. 1984. The fragmented forest. University of Chicago Press, Chicago,
I.L. 2llpp.
Helle P., and J. Muona. 1985. Invertebrate numbers in edges between clear-fellings and
mature forests in northern Finland. Silva Fenn. 19: 28 1-294. Found In: Hunter,
Malcom. 1990. Wildlife, forests and forestry: Principles of managing forests for
biological diversity. Prentice-Hall, Inc. Englewood Cliffs, N.J. 370 pp.
Hope, S., and W.C. McComb. 1994. Perceptions of implementing and monitoring
wildlife tree prescriptions on national forests in western Washington and Oregon.
Wildlife Society Bulletin 22: 383-392.
Hosmer, D.W. Jr., and S. Lemeshow. 1989. Applied logistic regression. John Wiley
and Sons, New York, N.Y. 307 pp.
Hunter, M.L. Jr. 1990. Wildlife, forests and forestry: Principles of managing
forests for biological diversity. Prentice-Hall, Englewood Cliffs, N.J. 370 pp.
INFO. Arc/Info Version 7. 1994. Environmental Systems Research Institute, Inc.
Redlands, C.A. 337 pp.
Jackman, S.M. 1974. Woodpeckers of the Pacific Northwest; their characteristics and
their role in the forest. M.S. Thesis, Oregon State University, Corvallis. 147 pp.
Johnson, D.H. 1980. The comparison of usage and availability measurements for
evaluating resource preference. Ecology 61: 65-70.
Karlsson, J., and S.G. Nilsson. 1977. The influence of nest-box area on clutch size in
some hole-nesting birds. Ibis 119: 207-211.
77
Kimmey, J.W., and R.L. Furniss. 1943. Deterioration of fire-killed Douglas-fir. USDA
Technical Bulletin 351. U.S. Government Printing Office. Washington, D.C.
61 pp.
Knight, F.B. 1958. The effects of woodpeckers on populations of the Engelmann spruce
beetle. Journal of Economic Entomology 51: 603-60 7.
Kotliar, N.B., and J.A. Wiens. 1990. Multiple scales of patchiness and patch
structure: a hierarchical framework for the study of heterogeneity. Oikos 59:
253-260.
Leopold, A. 1933. Game Management. Charles Scribner Sons. New York, N.Y.
481 pp.
Lundquist R.W., and J.M. Mariani. 1991. Nesting habitat and abundance of snagdependent birds in the southern Washington Cascade Range. Pages 22 1-239 L.
F. Ruggiero, K.B. Aubry, A.B. Carey, and M.H. Huff, technical coordinators.,
Wildlife and vegetation of unmanaged Douglas-fir forests. USDA Forest Service
General Technical Report PNW-GTR-285.
Madsen, S.J. 1985. Habitat use by cavity-nesting birds in the Okanogan National Forest,
Washington. M.S. Thesis. University of Washington, Seattle. 113 pp.
Mannan, R.W. 1977. Use of snags by birds, Douglas-fir region, western Oregon. M.S.
Thesis. Oregon State University, Corvallis. 113 pp.
Mannan, R.W., E.C. Meslow, and H.M. Wight. 1980. Use of snags by birds in
Douglas-fir forests, western Oregon. Journal of Wildlife Management 44: 787797.
Mariani, J.M., and D.A. Manuwal. 1990. Factors influencing brown creeper (Certhia
americana) abundance patterns in the southern Washington Cascade Range.
Studies in Avian Biology 13:53-57.
Marks, B., and K. McGarigal. 1995. FRAGSTATS: Spatial pattern analysis
program forquantifying landscape structure. USDA Forest Service General
Technical Report, PNW-GTR-351. 122 pp.
McClelland, B.R., and S.S. Frissell. 1975. Identifying forest snags useful for holenesting birds. Journal of Forestry 73: 414-417.
McClelland, B.R. 1977. Relationships between hole-nesting birds, forest snags and
decay in western larch, Douglas-fir forests of the northern Rocky Mountains.
Ph.D. Dissertation. University of Montana, Missoula. 495 pp.
78
McGarigal, K. 1993. Relationship between landscape structure and avian abundance
patterns in the Oregon Coast Range. Ph.D. Dissertation. Oregon State
University, Corvallis. 273 pp.
McGarigal, K., and W.C. McComb. 1995. Relations between landscape structure and
breeding birds in the Oregon Coast Range. Ecological Monographs 65: 23 5-260.
Mellen, T.K. 1987. Home range and habitat use by pileated woodpeckers. M.S. Thesis.
Oregon State University, Corvallis. 96 pp.
Mime, K.A., and S.J. Heji. 1989. Nest-site characteristics of white-headed woodpeckers.
1989. Journal of Wildlife Management 53: 50-54.
Naveh, Z., and A. S. Liebermann. 1984. Landscape ecology, theory and application.
Springer-Verlag, New York, N.Y. 356 pp.
Nelson, S.K. 1989. Habitat use and densities of cavity-nesting birds in the Oregon
Coast Ranges. M.S. Thesis. Oregon State University, Corvallis. 157 pp.
Neitro, W.A., V.W. Binkley, S.P. Cline, R.W. Mannan, B.G. Marcot, D. Taylor, and F.F.
Wagner. 1985. Snags. Pages 129-168 In: Brown, E.R. tech. ed. Management of
wildlife and fish habitats in forests of western Oregon and Washington. Part 2 Appendices. USDA Forest Service, Pacific Northwest Region, Portland, O.R.
Nilsson, S.G. 1984. The evolution of nest-site selection among hole-nesting birds: the
importance of nest predation and competition. Ornis Scand. 15: 167-175
Ormsbee, P. 1996. Selection of day roosts by female long-legged myotis (Myotis
volans) in forests of the central Oregon Cascades. M.S. Thesis. Oregon State
University, Corvallis. 63 pp.
Otvos, I.S. 1965. Studies on avian predators of Dendroctonus brevicomis le Conte
(Coleoptera: Scolytidae) with special reference to Picidae. Canadian
Entomologist 97: 1184-1199.
The effects of insectivorous bird activities in forest ecosystems: an
evaluation. Pages 341-374 In: J.G. Dickson et al., eds. The role of insectivorous
birds in forest ecosystems. Academic Press. New York, N.Y.
1979.
Otvos, I.S. and R.W. Stark. 1985. Arthropod food of some forest-inhabiting birds. The
Cannadian Entomologist 117:971-990
______•
79
Ramsey, F.L., M. McCracken, J.A. Crawford, M.S. Drut, and W.J. Ripple. 1994.
Habitat association studies of the northern spotted owl, sage grouse, and
N. Lange, L. Ryan, L. Billard, D.
flammulated owl. Pages 189-209
Brillinger, Conquest and J. Greenhouse (eds.). Case Studies in Biometry. John
Wiley and Sons, New York, N.Y. 496 pp.
Raphael, M.G., and M. White. 1984. Use of snags by cavity-nesting birds in the Sierra
Nevada. Wildlife Monograph No. 86. 66 pp.
Raphael, M.G., and M.L. Morrison. 1987. Decay and dynamics of snags in the
Sierra Nevada, California. Forest Science 33: 774-783.
1990. SAS/STAT Procedures Guide, Version 6, Third Edition, Cary,
N.C: 705 pp.
1997.
SAS/STAT software: changes and enhancements through release 6.12.
Cary,N.C. :ll67pp.
Schreiber, B. 1987. Bird use of snags on clearcuts in central coastal Oregon. M.S.
Thesis, Oregon State University, Corvallis. 63 pp.
Schreiber, B., and D.S. deCalesta. 1992. The relationship between cavity-nesting birds
and snags on clearcuts in wetern Oregon. Forest Ecology and Management 50:
299-3 16.
Sedgwick, J.A., and F.L. Knopf 1990. Habitat relationships and nest site characteristics
of cavity-nesting birds in cottonwood floodplains. Journal of Wildlife
Management 54: 112-124.
Swallow, S.K., and R.J. Gutierrez. 1986. Primary cavity-site selection by birds. Journal
of Wildlife Management 50: 516-583.
Thomas, J.W., G.L. Crouch, R.S. Bumstead, and L.D. Bryant. 1975. Silvicultural
options and habitat values in coniferous forests. In: Proc. symposium
management of forest and range habitats for nongame birds. USDA Forest
Service General Technical Report WO- 1.
Thompson, R.L. 1997. Home range and habitat use of western red-backed voles in
mature coniferous forests in the southern Oregon Cascades. M.S. thesis. Oregon
State University, Corvallis. pp.
USDA Forest Service. 1990. Land and Resource Management Plan - Umpqua National
Forest. Final Environment Impact Statement: Appendices - Volume II. USDA
Forest Service, Pacific Northwest Region. 315 pp.
80
USDA Forest Service and USD1 Bureau of Land Management. 1994. Record of
Decision for amendments to Forest Service and Bureau of Land Management
Planning Documents within the range of the northern spotted owl. Standards and
Guidelines for management of habitat for late successional and old-growth related
species within the range of the northern spotted owl. USDA Forest Service and
USD1 Bureau of Land Management. 74 pp.
Van der Kamp, B.J. 1991. Pathogens as agents of diversity in forest landscapes. The
Forestry Chronicle 67: 353-354.
Van Home, B. 1983. Density as a misleading indicator of habitat quality. Journal of
Wildlife Management 47:893-901.
Weikel, J. 1997. Habitat use by cavity-nesting birds in young thinned and unthinned
Douglas-fir forests of western Oregon. M.S. Thesis, Oregon State University,
Corvallis. 102 pp.
Wiens, J.A. 1976. Population responses to patchy environments. Annual Review of
Ecological Systematics 7: 81-120.
Wiens, J.A. 1989. Spatial Scaling in Ecology. Functional Ecology 3: 385-397.
Winkler, H., D.A. Christie, and D. Nurney. 1995. Woodpeckers: An identification
guide to the woodpeckers of the world. Houghton Mifflin Co. New York, N.Y.
406 pp.
Wright, K.H., and G.M. Harvey. 1967. The deterioration of beetle-killed Douglas-fir in
Oregon and Washington. USDA Forest Service Research Paper. Pacific
Northwest Region, Portland, OR. 22 pp.
Zamowitz, J.E., and D.A. Manuwal. 1985. The effects of forest management on cavitynesting birds in northwestern Washington. Journal of Wildlife Management 49:
255-263.
81
APPENDICES
82
APPENDIX A- Maps of eleven study sites showing habitat patch type and spatial
arrangement, and location of woodpecker nests at each site.
STUMP LAKE SITE
N
LEGEND
Neat,
A AS-breasted espauckec
• Hafry wood peck..
•
*
PII.Sedwooc*.ecker
Patth
1 Mthve FareS
2 Mitt,. lodgepole
ian
POWSITUb
6 ClearcuI wIIh
7 Clearcut with etmjbe-no snag
2 00
Woodpec ker nest locations over 200-Ha lands capes
In the Dia mond Lake Ranger District, Umpqua National Forest
Southern Oregon
1995-1996
0
200
400
600
800 100 0 Meters
FOREBAY SITE
LEGEND
a a a aa a aaaam
Nests
£ Red-breasted sapsucker
• Hairy woodpecker
a\.7a
aaaaaaaaa
a a a a a a a aaaa4a
aa
a
aaaaaaa
aa
a
a
a
aaaa
• Northern flicker
* Pileated woodpecker
Patch type
MatLts Forest
Shaiterwood
Clewout with snags
Clsarcut with shrubs
cleercut with shrub.-
snag
aa
a
a
a
kaa..
Wood pecker nest locations over 200-Ha lands capes
in the Diamond Lake Ranger District, Umpqua National Forest
Southem Oregon Cascades, 1995-1996
00
0
200
400
600
800
100 0 Meters
TRAP CREEK SITE
N
#81 111111 S
'S
LEGEND
A
Neste
A Red-breasted sapsuc ker
• Hairy woodpecker
•* Pfleated woodpecker
Nofthern flicker
Patch type
1 Mature Forest
3 PoIe(shrub
5 Clearcut with snags
6 Clearcut with shrubs
Wood pecker nest locations over 200-Ha lands capes
In the Diamond Lake Ranger District, Umpqua National Forest
Southem Oregon Cascades, 1995-1 996
200
0
200
400
600
800
100 0
Meters
00
z
•/
SPRUCE SITE
LEGEND
kor
t
it
mu
C
C
wE
o
m
a'
C 0)
o
0
Ms.
—xo
C
capes
National Forest
0
0
0
ID
0
0
0
0
c'J
0
0
0
o Meters
o
S
sEQ
Woodpec
in the Dia
Southern
00
LITTLE BEAR SITE
N
LEGEND
Nest.
£
Red-breasted sapsLIclcer
Hafry woodpecker
•• Naqthecn flicks,
*
wo*eoker
Patol, type
1 Mature Forest
2 Mature lodgepol.
Shellerwood
Clearciit with snags
Crewcut with siTub,
7 Clearcut vith
S
Wood pec ker nest locations over 200-Ha lands capes
In the DIa mond Lake Ranger District, Umpqua National Forest
Southern Oregon Cascades, 1995-1996
200
0
200
400
600
800
100 0
0
Meters
00
MOWICH SITE
N
LEGEND
I Sst
A Red-StasiS sapsucker
..
*
*
Hairy woodpecker
Northern flicker
Pileeled woodpecker
woodpecker
Patc htype
Mature Forest
She ito iwood
C15 Clearcut with snags
CIOaTCUt with ,hmbs
Wood pecker nest locations over 200-Ha lands capes
Inthe Diamond Lake Ranger District, Umpqua National Forest
South em Oregon Cascades, 1995-1996
2 00
0
200
400
600
800
100 0 Meters
z
/A I
A
4 <rn
/ '.Jtnuv
4
A
4.
4
a
L
.
4
4
••
4
:4•.
4
/ (4
4
4
4
4
4
4
4
4
<4
4
4
4
4
4
as
%A
a%
4
4
4
r
5
..c
S
4
.•
.
•
.
fl.
.
-.
.
.
.
.
—
.
VI
fl U
A
Y
.1
A
X
X
tS
/
.
.
A
A
A
A
V
UI hr
in
nI
i:;:!
U
ker
—
—
• ..
A
.
VW(
a
4
¼t
flr I<((<<(V<<<
((((4
44(t4(((€(
5((((((5-..
A
LEGEND
.7/
89
0
c'J
0
0
0
CD
0
0
0
0
0
0•
0 Meters
2
0
.xEO
•rn_iC0
mE
5 C.
C
capes
National Forest
Woodpec
In the Dia
Southern
A
VELVET CREEK SITE
ROUGH CREEK SITE
N
LEGEND
Nests
A Red-breasted sepsuckec
• Hakywoodpeck
•
Northern tUcker
Patch type
I Mature Forest
Pole/shrub
5 Cloarcut with snags
6 Clearcut with shrubs
..
I
Woodpec ker nest locations over 200-Ha landscapes
in the Dia mond Lake Ranger District, Umpqua National Forest
Southern Oregon Cascades, 1995-1 996
2 00
0
200
400
600
800
100 0 Meters
C
MAPLE CREEK SITE
N
LEGEND
Men
£ Red-breasled sapsuc ker
• Hairy woodpecker
•
*
woodpecker
Petch type
Mawr. rorest
Pol&eIwLt
Shfle,wood
Cleamut with snaga
Cleartut wilti shrubs
CIeawut with sirute -no snags
Wood pecker nest locations over 200-Ha lands capes
In the Diamond Lake Ranger District, Umpqua National Forest
South em Oregon Cascades, 1995-1996
2 00
0
200
400
600
800
100 0
Meters
—
N
WATSON CREEK SITE
LEGEND
Nests
sapsuc ker
A
• Hairy woodpecker
• Northern flicker
* Pileated woodpecker
+ Red-naped sapsucker
Patch type
1 Mature Forest
E21 5 Clearcut with snags
Clearcut with shrubs
2 00
Wood pecker nest locations over 200-Ha lands capes
In the Diamond Lake Ranger DistrIct, Umpqua National Forest
South em Oregon Cascades, 1995-1 996
0
200
400
600
800
100 0 Meters
____LEGEND
PYGMY KNOLL SITE
N
A
Nests
S Red-breasted saps
A
• Hefrywoodpecker
• Northern flicker
Patth type
1 Msttn Forest
Pole/skit
S Clearcut with Sn age
Wood pecker nest locations over 200-Ha landscapes
In the Diamond Lake Ranger District, Umpqua National Forest
South em Oregon Cascades, 1995-1996
2 00
0
200
400
600
800
1000 Meters
94
Appendix B. Weight file used in FRAGSTATS analysis to characterize vegetation
characteristics of 200-ha landscapes in the Diamond Lake Ranger District, Umpqua
National Forest, Southern Oregon Cascades, 1995-1996
BOUNDARY TYPE
WEIGHT
1-2
0.05
0.20
0.05
0.25
0.45
0.45
0.25
0.10
0.30
0.50
0.50
0.25
0.05
0.25
0.25
0.20
0.40
0.40
0.20
0.20
0.00
1-3
1-4
1-5
1-6
1-7
2-3
2-4
2-5
2-6
2-7
3-4
3-5
3-6
3-7
4-5
4-6
4-7
5-6
5-7
6-7
Appendix C. Class level indices generated in FRAGSTATS to quantify habitat characteristics for 11 200-ha landscapes where
woodpecker nests were located on the Diamond Lake Ranger District, Umpqua National Forest, Southern Oregon Cascades. 19951996.
SITE
Number
% Mature
forest
Forest
patch
density
Mean patch
of Nests
Stump Lake
19
43.7
Forebay
21
TrapCreek
size (ha)
Edge
density
(m)
contrast
% Core
area forest
Density of
core area
2.2
20.3
35.1
24.1
9.3
2.2
10.1
1.1
9.4
21.8
33.0
0.0
0.1
14
41.9
3.8
11.2
31.7
37.4
9.9
1.6
Spruce
6
94.8
0.55
173.3
6.5
0.96
64.7
0.55
Little Bear
18
58.9
0.54
109.5
31.2
13.3
16,6
2.2
Mowich
14
89.2
0.52
171.5
15.3
12.6
51.4
0.52
Velvet Creek
7
76.8
0.53
145.4
21.9
15.3
34.1
0.53
Rough Creek
13
41.7
0.57
73.6
34.5
39.2
6.9
1.13
Maple Creek
12
48.9
2.1
23.1
40.3
29.5
9.6
2.7
Watson Creek
13
60.9
1.7
35.4
55.2
37.6
9.8
2.9
Pygmy Knoll
19
35.4
1.6
21.7
14.5
22.3
15.1
0.54
Edge