Spring Bird Communities in the Oregon

Coast Range

Andrew B. Carey, Mary Mae Hardt, Scott P. Horton, and Brian L. Biswell

Authors

ANDREW B. CAREY is a research wildlife biologist,

MARY MAE HARDT is a data analyst, and SCOTT P.

HORTON and BRIAN L. BISWELL are wildlife biologists,

USDA Forest Service, Pacific Northwest Research Station,

Olympia, Washington 98502.

Abstract

Our objectives were to determine the value to birds of oldgrowth forests relative to mature and young forests in the

southern Oregon Coast Range. Special emphasis was placed

on cavity-using birds. We studied birds in 45 stands in 1985

and 33 stands in 1986. Over 60,000 individuals of 91 species

were counted; 989 observations on the foraging activities of

cavity-using birds were recorded; 277 nests of cavity users

were found and described; snag densities were estimated by

four size-classes and three decay-classes. We calculated a

birds-per-area index (BAI) from the counts and diversity

indices from the BAI. Bird species diversity and total bird

abundance did not differ significantly among the young,

mature, and old-growth stands. Fourteen species were most

abundant in old growth; 10 were cavity users (including the

crevice-nesting brown creeper and the spotted owl). Two species that do not nest in cavities, the western flycatcher and

the varied thrush were also abundant in young and mature

stands. Two, the marbled murrelet and the olive-sided flycatcher, were rare in young and mature stands. All the cavity

users (including the brown creeper) selected very large snags

for nesting; snags of the average sizes used by these birds

were larger than those normally produced in young stands.

Under current conditions, the cavity-using birds depend on

old growth.

Introduction

“Are there unique features, species, or important values associated with old-growth forests?” ask Franklin and others

(1981). They review the literature and ongoing research and

conclude that old-growth forests provide specialized habitats

and differ from both natural and managed younger forests.

Research shows some differences between managed forests

and old-growth forests in avian community composition

(Hagar 1960) and total bird abundance and constancy of

abundance (Bowles 1963). And although 18 or more species

of vertebrates appear to find optimal conditions in old growth,

quantitative avifaunal studies across stages of forest development are lacking in the Douglas-fir forests of western Oregon

and Washington (Meslow and Wight 1975, Meslow and others 1981). The Old-Growth Forest Wildlife Habitat Program

was chartered to quantify the value of old growth to wildlife

(Carey and Spies, this volume; Ruggiero and Carey 1984).

We began our research in the Oregon Coast Range in 1985

under the aegis of the Old-Growth Program.

Our objectives were to determine the value to birds of old

growth relative to young and mature Douglas-fir forests in

the Oregon Coast Range. In particular, we wanted to

123
determine if the bird communities in old growth differed

from the bird communities in mature and young forest in

total abundance, diversity (numbers of species and the degree

to which the communities were dominated by a few species),

composition of species, and structure (ranked abundance of

the species) because these are all components of biodiversity;

simple presence or absence of species does not reflect all the

important aspects of biodiversity, and few species in the

Pacific Northwest are so specialized that they would be expected to be confined to old growth (Meslow and others

1981). We also wanted to determine which species reached

maximum abundance in old growth and which, if any; were

found exclusively in old growth. We placed special emphasis

on cavity-using birds because Mannan and others (1980), in

an unreplicated study, report cavity-using birds to be strikingly more abundant in old growth than in younger stands.

And Cline and others (1980), Mannan and others (1980). and

Meslow and others (1981) express concern over the loss to

timber management of large, Douglas-fir snags that are

important to cavity-using birds.

Franklin and others (1981) list some structural features unique

to old-growth (as compared to young and mature) forests that

could be important to birds; we wished to determine whether

these features were important. These features and their

putative value to birds (and the tests we made) include:

l Large, old Douglas-fir trees have deeply furrowed bark

that provides a unique environment for bark arthropods

and may be important foraging substrates for bark-foraging

birds, especially the brown creeper. We test the hypotheses:

(a) young, mature, and old-growth stands do not differ in

the density of large (>lOO cm in diameter-at-breast height,

d.b.h.) Douglas-fir; (b) abundance of bark-foraging birds

is not positively correlated with the densities of large

Douglas-fir trees; (c) bark-foraging birds do not differ in

abundance among young, mature, and old-growth stands;

(d) brown creeper abundance is not correlated with the

density of large Douglas-fir trees; (e) brown creeper abundance does not differ among young, mature, and oldgrowth stands. Rejection of the last two hypotheses would

imply that brown creepers forage in large trees out of proportion to their availability relative to small trees. We

examined the foraging behavior of brown creepers to test

this implicit hypothesis.

l Two or more age-classes of conifers that form an overstory, midstory, and sometimes an understory result in a

vertical diversity of coniferous foliage that may support a

diversity and abundance of birds that forage among the foliage of trees (foliage foragers) that exceeds that in young

or mature forests. We test the hypotheses: (a) foliageheight diversity does not differ among young, mature, and

old-growth stands; (b) the abundance of foliage foragers

does not differ among young, mature, and old-growth

stands; (c) the diversity of foliage foragers does not differ

among young, mature, and old-growth stands; (d) the diversity of foliage foragers is not correlated with foliageheight diversity; (e) the abundance of foliage foragers is

not correlated with foliage-height diversity.

l Large, standing, dead trees may provide important nesting

substrate for cavity-using birds. We test the hypotheses:

(a) the density of large snags does not differ among young,

mature, and old-growth stands; (b) the abundance of

cavity-using birds does not differ among young, mature,

and old-growth stands; (c) cavity-using birds do not use

large snags for nesting out of proportion to their availability relative to small snags.

l Spatial diversity of vegetation brought about by gaps in

the canopy caused by the death of large trees may provide

for a greater diversity and abundance of birds in the understory and on the ground. We test the hypotheses: (a) spatial

diversity of vegetation does not differ among young, mature, and old-growth stands; (b) the diversity and abundance of birds associated with the forest floor do not differ

among young, mature, and old-growth stands.

Our final objective was to determine if the complex moisturetemperature gradient governing plant community composition in the Pacific Northwest (Franklin and Dymess 1973)

resulted in differences in bird species diversity or species

abundances among old-growth stands on different parts of

the gradient (wet, mesic, and dry sites). Franklin and others

(1981) discuss the value of streams in old growth. We do not

address streams here because the influence of small streams

and seeps on upland, spring bird communities in the Oregon

Coast Range was reported by Carey (1988).

Methods

Experimental Design

Study stands were selected under the vegetation community

ecology portion of the Old-Growth Program (Carey and

Spies, this volume), but we were unable to find enough

stands for three complete replicates of the Program’s design:

three young, three mature, three wet old-growth, three dry

old-growth, and three mesic old-growth stands. Forty-five

stands were studied in 1985: 8 young, 10 mature, 14 mesic

old-growth, 8 dry old-growth, and 5 wet old-growth stands

(see frontispiece). In 1986, because of cuts in funding, only

33 stands were studied: 6 young, 8 mature, and 10 mesic

old-growth, 5 dry old-growth, and 4 wet old-growth stands.

Young and mature stands were not classified into moistureclasses, but spanned the same moisture gradient that the

old-growth stands spanned. We could not find stands of 100

ha or more as called for in the research plan. Stand size

124 I
averaged 29 ha, ranging from 14 to 62 ha. Two small oldgrowth stands studied in 1985 were replaced with larger

stands in 1986. Study stands were in four large clusters:

between Corvallis and Yachats, west of Drain, northwest of

Roseburg, and between Roseburg and Coos Bay, Oregon.

The clusters covered the southern Coast Range western

hemlock forest type but also included the coastal Sitka

spruce forest type near Yachats, the Umpqua Valley margin

mixed-conifer forest type northwest of Roseburg, and the

southwest Oregon mixed-evergreen forest type near Remote.

Each cluster contained young, mature, and old-growth

stands, but not enough stands of each type to be treated

separately.

Douglas-fir was a dominant species in each stand. Young

stands were 40 to 72 years old; mature stands were 80 to 120

years old, old-growth stands were 200 to 525 years old. One

old-growth stand had a mixed-aged canopy of trees 130 years

old and old-growth trees of unknown age, d.b.h. of 100 cm

or more, and density of 17.4 per hectare. The old-growth and

mature stands and three of the young stands originated after

catastrophic wildfire. Five of the eight young stands originated after human disturbance (logging or clearing) as

evidenced by stumps, old roads, or railroad grades.

Sampling Plan

We located 12 points 100 m apart along a transect through

each stand; our stands were not large enough to use the Program’s recommended 150 m between points. Because stands

were small and we maintained a 75-m buffer along stand

edges, the points systematically covered the interior of each

stand. The smallest stands were too small for 12 points. One

stand had only 7 points (dropped in 1986), one had 10 points

(dropped in 1986). and three had 11 points (two dropped in

1986). These points served as centers for nested circular plots

for describing vegetation and for bird counts; they also delineated segments of 30-m-wide strip transects used to sample

snags.

Sampling Techniques

Birds-Pilot studies (Manuwal and Carey, in press) compared line transects, variable-circular plots, and territory mapping as methods for estimating bird abundance and describing bird communities for contrasting young, mature, and

old-growth forests. Variable-radius circular plots (Reynolds

and others 1980) with 12 sampling points and six visits gave

the best return per unit effort in determining species presence

and abundance, but densities differed from territory mapping

by 13 to 41 percent. Major differences were overestimates

from counting birds more than once, particularly birds of

species whose home ranges were large relative to spacing

between the plots or that could be detected at long distances

(for example, more than 75 m).

With the pilot study as the basis for our sampling, we recorded all birds seen or heard during 6 to 11, early morning,

8-minute visits during late April, May, and June at each of

the sampling points in the stands. Species not commonly

recorded at sampling points were recorded if seen while the

observer walked between points and during searches for nests

and observations of foraging behavior that immediately followed the count surveys; 4 to 5 hours were spent in each

stand on a sampling day. Sampling was not done on windy

or rainy days. The minimum number of visits to a stand was

six in a year. We tried to visit stands with less than 12 points

more often than the stands with 12 points (appendix tables

14, 15). For example, the maximum was 11 visits to the

stand with 7 points. In 1985, all but three stands had six to

eight visits, with the range caused by rainy days, observer

illness, and other random events. In 1986, all but two stands

were visited seven times (the two had six visits). As predicted by the pilot study, species richness reached an asymptote before 72 8-minute counts (six visits to a stand with

12 points) had been done.

We estimated the distance to each bird detected that was not

flying through or over the stand during the 8-minute counts.

Distance estimation was aided by two flags 25 m from each

point, flags midway between points, and by rangefinders.

Distances more than 100 m were not recorded because we

and our field biologists concluded that estimating distances

beyond 100 m with a 20-percent precision was impossible.

We made a strong effort to avoid counting the same bird

more than once from the same point. We and our field biologists believe that we were successful in minimizing double

counting. If a bird could be heard from more than one point,

it was recorded only at the point closest to it. The average

(among species) third quartile of detection distances was

51 + 0.4 (SE) m and did not differ among young, mature,

and old-growth stands. Because we used only detections within the third quartile for calculating abundance indices (see

section on data analysis), any bias (dependence) from assigning a bird to only one point should have been minimized.

Controlling for differences among observers-Eleven biologists counted birds in 1985 and eight counted in 1986. Five

counted birds in both years. All had experience in bird identification before employment, and all were trained for 2 to 3

weeks before sampling each year they participated in

sampling.

Training consisted of instruction and practice in the field

and written protocols that documented objectives, methods,

assumptions of techniques, and consequences of violating

assumptions. Protocols were reviewed in group discussions

and implemented in the field both by groups and by pairs of

biologists. All were provided with binoculars, field guides to

125
bird identification, recordings of bird calls and songs in northem California and southern Oregon, as well as opportunities

to review recordings based on national and regional bird

calls and songs. A written, phonetic guide to bird calls and

songs (Carey and others 1990) was developed by the group,

based on their experiences in the southern Coast Range, and

all observers were provided with a copy. Training in bird

identification, identification of calls and songs, and aural

distance estimation in the field was provided to the group

before sampling began; individuals had opportunities to

practice alone. The biologists were trained in the use of

rangefinders and ocular estimation of distance on courses

with targets at various, measured distances. Targets were

placed at measured distances near offices so rangefinders

could be calibrated daily (flags 25 m from each station

allowed checking of rangefinders during actual surveys).

During surveys, rangefinders were used to check ocular and

aural estimates of distances to birds. Flags at 25-m intervals

along the transect allowed observers to continually check

their distance estimates for birds that were too far away to be

visually or aurally located in a specific tree. We and our field

biologists believed that we maintained a high degree of accuracy in bird identification and distance estimation throughout

the sampling.

Observers were in three Oregon locations in 1985, with four

in Corvallis, two in Lorane, and five in Winchester: In 1986,

three biologists were in Corvallis and five were in Sutherlin.

Within each geographic area, observers were systematically

rotated among the stands being sampled; young, mature, and

old-growth stands were sampled in each area. Biologists in

each geographic area (three areas in 1985, two areas in 1986)

regularly met to discuss the birds seen and heard and to review one another’s data sheets. Regular telephone contact

was maintained between the geographically separated groups

during the sampling season to discuss methodology and the

birds being seen and heard.

Nests and foraging behavior-After each morning’s bird

counts, we searched the stands for nests and recorded foraging behaviors of cavity-using birds. Nests, nest trees, and

nest environments were described (Nelson 1989). For foraging behaviors, we recorded the vertical location by foliage

strata (upper, middle, or lower canopy; understory; shrub

layer; ground), the horizontal location (mainstem; inner, center, or outer branch; log), the species of tree, the substrate

(bole; large, medium, or small branch; twig; shrub), the condition of the tree (live good, live poor, snag decay-class), the

d.b.h. of the tree (0-9, l0-19, 20-49, 50-99, and > 100 cm),

the dominance status of the tree (suppressed, subordinate,

dominant/codominant), and the object (foliage, bark, live

wood, dead wood, flower, bud, insect, and other) for the first

foraging activity observed for each bird seen.

Vegetation-Vegetation was characterized on two scales:

13-m-radius plots for ground cover, shrub, and midstory variables; and 25-m-radius plots for site and overstory variables.

Cover variables included fallen trees by three decay-classes

(combined from Franklin and others 1981): 1, intact; 2, bark

sloughing to absent, sapwood well-decayed; 3, tree completely in contact with the ground, bark absent, and all wood

well-decayed). Other cover variables were herbs, ferns

(mostly sword fern), berry-producing deciduous shrubs

(mostly blueberry and blackberry), other deciduous shrubs

(mostly oceanspray, filbert, and maple), evergreen shrubs

(mostly salal, Oregongrape, Pacific rhododendron), broadleaved evergreen midstory trees, deciduous midstory trees,

and needle-leaved midstory trees, Overstory variables included canopy cover of three classes of trees (deciduous,

broad-leaved evergreen, and needle-leaved evergreen), counts

of snags by three decay-classes (combined from Cline and

others 1980): 1, bark and branches mostly intact, sapwood

firm; 2, limbs stubs to limbs absent, sapwood soft; 3, welldecayed, bark and sapwood sloughed). We also counted trees

by diameter-classes (l0-49 cm, 50-99 cm, and 1100 cm) for

Douglas-fir, western hemlock, cedars-Port-Orford-cedar,

incense-cedar, and western redcedar, Pacific madrone, giant

chinkapin, bigleaf maple, other conifers (mostly grand fir),

and other deciduous trees. Snags sampled along the transects

were measured and described in more detail than those in the

circular plots, and their use for nesting and roosting by

cavity-using birds was compared to that of snags generally

available (Nelson 1989).

Data Analysis

Observations of moving birds, birds more than 75 m from a

sampling point, or birds recorded only once in a stand were

discarded before calculating indices of birds per effort (BEI)

and birds per area (BAI). We did this to avoid counting

individual birds more than once, eliminate the observations

With the most error (the most distant observations), reduce

among-observer differences in effective detection distances,

eliminate transient species from the counts, and maintain

comparability with the results of the bird community studies

in the Oregon Cascade Range, the southern Washington

Cascade Range, and the regional analysis of the Old-Growth

Program data.

The recorded observations for each species were examined to

determine if the rate of cue (call, song) emission varied with

time. The black-headed grosbeak, Swainson’s thrush, and

western tanager were not detected during the early counts.

We subtracted the sampling done in the first 5 to 18 days

(depending on species) from the effort to adjust for the periods when each species was not present (or not singing).

From these reduced data, we calculated bird species richness

(number of species by stand) and an index to abundance

based on effort-mean number per count per species per

stand (BEI).

126
For analyses related to community structure and bird species

diversity, we calculated an index to abundance based on area

sampled per species (BAI). Placing the birds on an areasampled scale allowed calculation of diversity indices and

examination of community structure (ranked abundance)

(Hutto and others 1986). Such analyses cannot be done

reliably with simple count data.

First, we eliminated effort and observations of observers who

seemed to have especially poor sensitivity to the calls or

songs of particular species (these are known as “window species” for that observer, Kepler and Scott 1981). Poor sensitivity was defined as having a mean number per count less than

50 percent of the median (among observers) mean number

per count. For the 2 years, 15 of 929 observer-bird species

combinations were dropped. Window species did not appear

to reflect differences in the hearing, experience, or awareness

of the observers. They seemed to be unique interactions

between particular species and individual observers.

We then examined the detections-versus-distance curves by

stand type to determine if differences existed among young,

mature, and old-growth stands (we found none). From the

distributions of birds detected over distance, we calculated

the third quartile detection distance for each species. We

used this distance as an effective radius of detection for that

species and calculated the area sampled around each point.

The third quartile proved to be a good approximation of the

shoulder in the detection curve-the distance at which a

marked decline in numbers of birds was detected. The abundance index was calculated as the numbers of cues of individual birds detected within the third quartile divided by the

area sampled (number of points times area sampled per point

times the number of visits per point). Abundances are reported on a birds-per40-ha scale. We calculated coefficients

of variation for the density indices for each stand and standclass.

For species that were detected mostly (> 270 percent) by their

songs, we deleted observations of nonsinging birds; later we

doubled the BAI of the songs-only species, on the assumptions we were recording only males and that all males were

mated (Emlen 1977, Reynolds and others 1980).

Many sources of bias and error are possible in count indices

and cue-density indices (Dawson 1981, Emlen 1977, Hutto

and others 1986, Verner 1985; see Ralph and Scott 1981 for

an extensive treatment). But our BAI require fewer assumptions and incorporation of less error and bias than the abundance index, BEI (Carey 1983, Ramsey and others 1987,

Raphael 1987a). Our BAI is a measure of bird density only

to the extent that bird call-and-song counts per unit area are

a measure of density. Some birds may not be counted, and

some may be counted twice. If such a sampling error differs

among bird species, among groups of observers, or among

stand types, then the BAI (and the BEI) would be biased.

Placing the birds on an area-sampled scale helped to account

for differences in detectability among species. Elimination of

long-distance detections and window species was designed to

reduce among-observer variability. The remaining amongobserver variability was evenly apportioned among the stands

through our systematic rotation of observers. Calculating

species-by-species third quartiles of detection distances was

an effort to reduce the errors in identification of species and

estimation of distances in the area of marked decline in

detectability. We could not use mathematical models of the

decline in detectability because the 27 species for which we

had numbers of detections sufficient to model detectability

differed markedly in the shape of the detectability curves.

And we could not relate the shape of the detectability curve

to either the cue quality (strength and pitch of calls and

songs) or to the vertical position of the species in the canopy.

Therefore, we could not choose a model to fit all species, or

several models that could be applied to species of like songs

and calls or like positions in the canopy.

In both years, five species exhibited “spikes” (high counts in

the first few meters followed by a sharp reduction in counts

and eventual additional decline in dectectability), six species

had “donuts” (low counts in the first few meters, followed by

higher counts, then by declining counts), four species had

spikes and donuts, and eight species differed in pattern between years. We could not relate patterns to cue quality or

usual location of the species in the canopy. Deletion of

nonsong cues from songs-only species did reduce the spikes.

Using the the third quartile distances typically encompassed

the bulk of the donut. Thus, we effectively reduced some of

the error from differences among species. Error in the BAI

was likely to be greater in the less abundant and less detectable species, simply because of sample sizes. We chose diversity indices (Magurran 1988) and made comparisons of

community structure with these errors in mind.

Margalef’s index (MI) accounts for variability in species

richness by weighting the number of species by the total

number of birds present; thus, MI based on BAI should be a

better measure of richness than number of species based on

simple counts. The Berger-Parker index (BPI) expresses the

degree to which the most abundant species dominates the

community and is thus robust to errors in the estimates of

species of low abundance. We used Kendall’s coefficient of

concordance (Zar 1984) to test differences among age-classes

and moisture-classes in the ranked abundance of species, and

we used Kendall’s coefficient of rank correlation and its

graphical representation (Sokal and Rohlf 1981) to display

the results of the analyses of ranked abundance. We applied

this analysis only to species that occurred in at least 90 per127
cent of the stands in any one stand type (young, mature, dry

old-growth, mesic old-growth, wet old-growth) to eliminate

rare species from the data set. In 1985, these tests were based

on the 16 most abundant species, and, in 1986, on the 14

most abundant species. All these species were detected 100

times or more during the counts. Error in the estimates of

species of low abundance was not important to the analyses

of community structure.

We used direct gradient analyses (box-and-whisker plots and

scatter plots) to explore our data. We were particularly interested in how much variability was in each variable-where

that variability lay in relation to stand-age and environmental

gradients, how observations on each variable were distributed

in a statistical sense, and how variability changed along the

distributions. Correlation coefficients (linear correlations,

correlations with log-transformed variables, and rank correlations) were used to identify redundancies among the variables

and to quantify bird species’ responses to gradients and relations between gradients.

Parametric and nonparametric (Kruskal-Wallis tests) analyses

of variance, Mann-Whitney U-tests, and median tests were

used to examine the statistical significance of comparisons

among categories. Bartholomew’s test for gradients in proportions was used to examine patterns of abundance (proportions

of stands in which the species was present) of birds of low

abundance across age-classes (Fleiss 1973); all recorded observations were used to determine presence and absence. Because our study sites and sampling points were not Selected

randomly, levels of significance are biased. But because we

intentionally sampled a wide range of variation in stands in

the southern Coast Range, we maximized variability and the

significance levels should be conservative (Gauch 1982)-

our P-values are probably larger than those a random sample

would have produced. The generalizability of statistical or

mathematical models and predictions derived from the data

is unknown, however. As with any study, extrapolation

beyond the bounds of the conditions examined would be

risky; the degree of risk is unknown. We recognize that the

power of statistical tests is low when variability is high and

sample sizes are small. We caution the reader that failure to

detect differences under these conditions does not necessarily

indicate that differences do not exist, only that the data did

not support rejection of the null hypothesis.

We examined bird community attributes and species’ abundances on two levels of gradients. The first level included

stand age (in years, sometimes log-transformed), stage of forest development (young, mature, old-growth), and moisture

categories (dry, mesic, wet). These first-level gradients reflect

complex interactions of site and the process of forest

development.

The second level included gradients based on cover-classes

and counts made at the sampling points or along transects.

These values were averaged for each stand, classes were combined, and the BPI was calculated. The second-level gradients

we developed were density of trees 100 cm or more in d.b.h.;

diversity of canopy conifer sizes (BPI based on density of

trees in the three size-classes); density of broad-leaved evergreens (Pacific madrone and giant chinkapin) in the canopy;

density of slightly to moderately decayed snags 50 cm or

more in d.b.h.; density of slightly to moderately decayed

snags 100 cm or more in d.b.h.; cover of deciduous trees in

the midstory and understory; cover of ferns, herbs, and berryproducing shrubs less than 2 m tall; cover of evergreen shrubs

less than 2 m tall; and the proportion of cover less than 2 m

tall that was ferns, herbs, and berry-producing shrubs.

Results

Characteristics of Old-Growth Stands

Old-growth stands were easily distinguishable from young

and mature stands on the basis of density of Douglas-fir trees

by diameter-class (table 1). Discriminant analysis using the

three density variables correctly classified 93.6 percent of

the stands (P < 0.01); one mature stand was classified as old

growth, one as young; one young stand was classified as mature. The density of coniferous trees 100 cm or more in d.b.h.

was positively correlated with stand age (fig. 1, r = 0.78,

P < 0.01).

The vertical diversity of conifers (as measured by the BPI)

in the canopy was positively correlated with stand age (fig. 2,

r = 0.51, P < 0.01) and varied almost three-fold among

stands. The BPI was significantly different among the young,

mature, and old-growth stand types (Kruskal-Wallis test,

Table l-Density of Douglas-fir by diameter-class

and age-class of stands in the southern Oregon Coast

Range, 1985-86; 8 young, 10 mature, and 29 oldgrowth stands were sampled

Density (stems per hectare)

Diameter-class

l0-49 cm

50-99 cm

> 100 cm

Ageclass

Young

Mature

Old

Young

Mature

Old

Young

Mature

Old

Mean

269.7

118.8

27.4

29.3

64.4

24.8

1.5

6.6

22.3

Standard

error Mode

29.0 213.4

19.2 74.8

6.2 .O

6.9 20.4

8.1 54.0

2.6 33.6

. 6 .O

2.6 .O

1.8 16.6

128


Table 3Species comprising 15 percent of aU observations 

1” 45 stands in 1985 and 33 stands in 1986 in the southern 

Oregon Coast Range 

1985 ,986 

Species Rank Number Rank Nunter 

Table 4-Mean number of species per stand by age-class and 

moisture-class, based on counts of stationary birds within 15 m 

of sampling points 1” the southern Oregon Coast Range, 1985. 

86 (species mast have occurred at least twice in a stand to be 

counted) 

correlation between total counts and BAI was much lower 

across species (r = 0.74, P < 0.01). reflecting the information 

gained by accounting for differences in detectability. 

The same eight species accounted for 75 percent of all observations in both years (table 3). Seven species were recorded 

in 1985 that were not recorded in 1986: black-capped chickadee (39 observations, primruy habitat: deciduous and deciduous/conifer forests), mountain quail (three observations, early 

stages of forest development), ruby-crowned kinglet (two 

observations, late stages of coniferous forest development), 

ruffed grouse (two observations, deciduous forests), Townsend’s solitaire (seven observations, early and late stages of 

forest development), white-brewed ““thatch (two observations, late stages of forest development), and western woodpewee (two observations, late stages of forest development) 

(habitat associations from Brown 198.5). Species recorded 

only in 1986 were chipping sparrow (four observations, early 

stages of forest development) and house wren (seven observations, shrub stages of forest development). Lists of species’ 

BAI by age-class are in appendix tables 12, 13. Sampling 

efforts are in appendix tables 14, 15. 

Table S-Mean values of MargalePs Index (MI) of richness 

and the Rerger-Parker index of dominance @PI) applied to 

avian species birds-per-area index by age- and molstureclass in the southern Oregon Coast Range, 1985.86 

MI, 1985 3.2 3.2 3.1 0.99 3.3 3.0 3.2 0.34 

BPI. 1985 4.6 4.0 4.1 .39 3.9 4.2 4.0 -47 

Samples” 8 10 27 8 14 15 

MI 1986 

BPi, 1986 

3.3 2.6 3.0 0.01 3.3 3.0 2.6 0.14 

4.5 4.6 4.8 .89 5.6 4.5 4.4 -1s 

samples’ 6 8 19 5 10 4 

Old 

Species Diversity 

The mean number of species per stand (based on co”nts) 

did not vary with age-class (Kruskal-Wallis, P = 0.98) or 

moisture-class (P = 0.51) in 1985. In 1986, mature stands 

had fewer species than young or old-growth stands (table 4; 

Kruskal-Wallis, P < O.Ol), but no significant difference was 

found among moisture-classes (Kruskal-Wallis, P = 0.24). 

The difference in richness was due to the absence of some 

uncommon species in the mature stands. Margalef’s index to 

richness displayed tlx same pattern a~ the counts-mature 

stands had fewer species than young and old-growth stands 

in 1986 but not in 1985 (table 5). Margalef’s index did not 

differ sig”iCicantly among moisture-classes. The BergerParker index of dominance (and evenness) showed no 

differences among stand types (table 5). 

Patterns of Abundance 

The mea” number of birds counted per stand in 1985 

(570) did not differ significantly (P = 0.85) among ageclasses; in 1986, fewer birds were counted in mature stands 

(mean = 471) than in young (mean = 489) and old-growth 

(mean = 528) stands (analysis of variance, P < 0.05). Ranked 

131 
Young Mi3hlW Old Table ‘I--Mean bird-per-area indices of species associated 

with young forests in the southern Oregon Coast Range, 

1985.86 

Age-class 

Species Young Mature Old-gropTh p” 

Black-headed grosbeak 3.90 0.79 0.37 * 

Da*syed jmco 7.76 4.39 2.06 * 

E”ening grosbeak 2.96 5.66 1.63 ** 

Flammmd’r flycatcher u.97 20.26 6.94 * 

Hermit warbler 69.59 41.18 48.34 * 

Hutton’s vireo 6.66 78 1.62 ** 

Nanhville rarbkr 1.84 .69 .71 * 

Table &Mean birds-per-area indices (numbers per 40 ha) 

of birds associated with old-growth forests in the southern 

Oregon Coast Range, 1985.86 

L1 *P < 0.1” in 1 year: ** P < 0.10 in 2 years: KlnskdWallis tea 

-.. n ._ 

Agezlarr Table &Mean an proportion proportion of young, mature, mature, and old-growth old-growth 

stands in which ch selected selected species species of low abundance abundance occurred occurred in 

Species Young Mature Old-grow* P the southern Oregon Coast Range, 1985.86; 1985.86; al,l observations observations 

recorded were ‘e used 

Brown creeper 16.66 28.66 34.24 ** 1 1 

Chestn”t-backd chickadee 52.06 61.88 101.62 ** Age-class 

Hairy woodpecker .74 1.10 1.79 * 

Olive-sided flvcatcher .06 .03 .47 * Species Young Mature Old-grow* P’ 

Fikated waodpwker .o* .2s 41 

Red-breasted nulhatch 3.14 6.48 9.30 

Kdbreasted sapsucker .12 .90 1.02 

Varied thruEh 4.82 15.12 14.75 

Western flycatcher 49.28 34.57 60.84 

Wmdpeckerrb 38 2.25 3.22 

Ohr cavity csersC 71.88 97.08 145.27 

Bark foraaersd 20.68 37.39 46.35 

** 

** 

** 

11 

** 

** 

** 

*1 

abundance did not differ among age-classes in 1985 (for 16 

species, fig. 5) or in 1986 (for 14 species, fig. 6) (Kendall’s 

coefficient of concordance, P -C 0.01, Kendall’s coefficient of 

rank correlation, P -C 0.01 for all pairwise comparisons). 

Nine species reached maximum abundance in old growth 

(table 6), including all the common cavity-using birds. The 

varied thrush was more abundant in mature and old-growth 

stands than in young stands. The varied thrush was the only 

species associated wilh old forests that also showed a preference for a moisture-class (wet stands in both years, KruskalWallis test, P < 0.05). Moisture prcfercnces of other species 

will be discussed below in relation to the eradient in mooorsolThem t&r .56 .88 93 

So*empygmy-owl 38 75 .59 

Olive-sided tlycatcher 31 .38 .78 

Pileared wocdpecker .69 .94 1.00 

Red-breanred raps”cker 31 .44 .87 

Sported owl .cu .oo .24 

Marbled murrele1~ .oo so .83 

“aux’s swift .w .29 39 

warbler, chestnut-backed chickadee, golden-crowned kingler, 

Hammond’s flycatcher, hermit warbler, Huaon’s vireo, purple 

finch, westcm flycatcher, western tanager, black-headed grosbeak, and yellow-rumped warbler) and forest-floor bids 

(American robin, blue grouse, dark-eyed junco, hermit thrush, 

song sparrow, Swainson’s thrush, varied thrush, Wilson’s 

warbler, winter wren, and wrentit) as groups did not differ 

significantly in abundance among age-classes (P > 0.10, 1985 

and 1986). Eleven species were most abundant in young 

stands (table 7). One, the purple finch, was listed by Brown 

(1985) as preferring old growth; our data suggest that it does 

not. L . 

tion of understory cover that was herbs, ferns, and berryproducing shrubs. Woodpeckers as a group, other cavity users 

Proportional occurr~~~ccs ol species of low abundance reas a group, and bark gleaners reached maximum abundance inforced many of the associations with old growth shown by 

in old growth (table 6). Foliage foragers (black-throated gray densities in table 6 (table 8). All of these species showed a 

132 
significant increase in abundance across the three age-classes

(Bartholomew’s test, P < 0.05). In addition, the northern

flicker and northern pygmy-owl increased in abundance with

stand age. All patterns displayed in tables 4 to 6 were consistent between years, except that evening grosbeaks were less

than one-tenth as abundant in old-growth and mature stands

and twice as abundant in young stands in 1986 as in 1985.

All abundances were of the same magnitude between years

except that chestnut-backed chickadees were one-third,

orange-crowned warblers one-fourth, and western tanagers

one-half as abundant in 1986 as in 1985.

Three species that were not commonly found within 75 m

of the sampling points were the marbled murrelet, the spotted

owl, and Vaux’s swift. They showed a pattern of increasing

abundance with age-class (table 8; Bartholomew’s test,

P < 0.05). The marbled murrelet was recorded only in mature

and old-growth stands near Corvallis (Carey 1989; Nelson

and others, in press).

Responses to Gradients

Bark foragers (hairy woodpeckers, pileated woodpeckers,

red-breasted sapsuckers, brown creepers, and red-breasted

nuthatches) were not significantly correlated (using Pearson

product-moment correlation) with the density of large trees

in 1985 and showed only a weak positive Pearson correlation

in 1986 (r = 0.45, P < 0.01) because of a positive response

by the red-breasted nuthatch. A simple linear regression of

bark-forager abundance on large-tree density had a positive

slope significantly different from zero (P < 0.05) in both

years. When we truncated the gradient at 20 large trees per

hectare (about the mean value for trees > 100-cm in d.b.h. in

old growth) the increase in the slope was marked. When we

examined the correlations between large trees and barkforager abundances for young and mature stands separately

from old growth, significant positive Pearson correlations

were found in both years (1985, r = 0.71; 1986, r = 0.75;

P < 0.01). Brown creeper abundances were positively correlated with the density of large trees in both years (r = 0.75 in

1985, P < 0.01; r = 0.62 in 1986, P < 0.05). Positive Pearson

correlations were found for pileated woodpeckers in 1985

and red-breasted sapsuckers in 1986. Spearman rank correlations were positive and significant in both years for brown

creepers and bark foragers, as a group, across the entire largetree gradient (P < 0.10).

Few positive Pearson correlations were found between cavityusing birds and densities of small, medium, large, and very

large snags. When we examined young and mature stands

alone, the red-breasted nuthatch, chestnut-backed chickadee,

brown creeper, and northern pygmy-owl, as a group, were

positively correlated with the density of very large (> 100-cmd.b.h.) snags (r = 0.71 in 1985, P < 0.01; r = 0.73 in 1986,

P < 0.05). Chestnut-backed chickadees accounted for most of

this positive response (r = 0.62 in 1985, P < 0.05; r = 0.67 in

1986, P < 0.05). Positive rank correlations (P < 0.10) were

found between very large snags and all cavity-nesting species,

brown creepers, woodpeckers as a group, and other cavity

nesters as a group in both years (except hairy woodpeckers

in 1985 and northern flickers in 1985 and 1986). Rank correlations with very large snags (0.28-0.55) were higher than

rank correlations with large snags (0.17-0.45), indicating that

very large snags accounted for a substantial portion of the

correlations with large snags.

Only one consistent pattern of positive response was obtained when we examined forest-floor-associated birds relative to the proportion of vegetative cover less than 2 m tall

that was herbs, ferns, or berry-producing shrubs, which is

also a site-moisture indicator, and the cover of evergreen

shrubs. The varied thrush was positively correlated with the

proportion of herbs, ferns, and berry-producing shrubs in

both years (P < 0.05, Pearson’s r = 0-44-0.54) and negatively

correlated with evergreen shrubs in both years (P < 0.05,

Pearson’s r = -0.43 in both years), reflecting its preference

for wet sites. Rank correlations between ground-associated

birds as a group and the proportion of herbs, ferns, and berryproducing shrubs were positive in both years (r = 0.35, 0.37,

P < 0.05).

We found no consistent pattern of positive responses between

the abundance and diversity (MI, BPI) of foliage foragers

and coniferous foliage-height diversity (BPI). Similarly,

we found no consistent pattern of positive responses when

we examined the diversity of hardwood-associated species

(black-throated gray warbler, black-headed grosbeak,

Hutton’s vireo, purple finch, Swainson’s thrush, warbling

vireo, black-capped chickadee, ruffed grouse, and downy

woodpecker) in relation to total deciduous hardwood cover

(shrub, understory, and midstory). Rank correlations between

the abundance of hardwood-associated birds as a group and

hardwood cover were significant in both years (r = 0.33,0.44,

P < 0.05).

Nests

We located 277 active nests of nine species of cavity-using

birds. All species preferred Douglas-fir snags more than

50 cm in d.b.h. Mean nest-tree d.b.h. ranged from 54 cm for

the northern pygmy-owl to 113 cm for the red-breasted sapsucker; the mean was 94 cm (Nelson 1989).

Foraging Behavior

We recorded 989 foraging bouts by six species of cavityusing birds (table 9). Pileated woodpeckers concentrated

their activities in the upper and mid-canopy in Douglas-fir,

as did red-breasted nuthatches. Pileated woodpeckers concentrated on tree boles, whereas the nuthatches used small, medium, and large branches in addition to the tree bole. Pileated

133
Table 9-Percentage of common (> 14 percent) foraging activities by bird species, location in the forest, tree characteristics, and

object for cavity-using birds in the Oregon Coast Range, 1985-86

ChestnutRed-breasted Pileated backed Red-breasted Brown

sapsucker woodpecker chickadee nuthatch creeper

99 156 I

Sample size 33 323 65 313

Vertical location:

Upper canopy

Midcanopy

Lower canopy

Understory

Horizontal location:

Mainstem

Inner branch

Center branch

Outer branch

54

22

17 38

36 49 30

22 30

20 32

19

47

23

35

14

26

86 72 83 37 87

40

16

16

35

52

Tree species:

Douglas-fir

Western hemlock

Bigleaf maple

Substrate:

Tree bole

Large branch

Medium branch

Small branch

Tree condition:

Live

Decay-class 1

Decay-class 2

Diameter-class:

0-9 cm

10-19 cm

20-49 cm

40-l00 cm

>lOOcm

Tree status:

Suppressed

Subordinate

Dominant

65

17

44

15

35

71 82 43

21

71

84 72 75 12

20

48

31 89

22

19

29

85 64

23

35

34

24

92 76 84

22

34

43

59

28

38

45

26 41

48 65 41

40

18 19

44 22

34 52

27

20

44

24

80 80 62

Object:

Foliage

Bark

Dead wood

Live wood (sap)

54

24

60

48

30

34

51

14 79

31

32

woodpeckers preferred large trees ranging from live trees in

good condition to snags that were slightly to moderately

decayed. Nuthatches concentrated on live trees.

Red-breasted sapsuckers and chestnut-backed chickadees also

used the upper canopy, but made greatest use of the middle

to lower canopy, as did hairy woodpeckers and brown

creepers. Sapsuckers, woodpeckers, and creepers concentrated

on the boles of trees, whereas chickadees foraged among

branches, especially the outer branches. Chickadees foraged

mostly on small branches. Douglas-fir was the primary species used, but sapsuckers also used bigleaf maple and western

hemlock. All concentrated on live trees in good condition,

with hairy woodpeckers making significant use of moderately

decayed snags. Chestnut-backed chickadees foraged across

diameter-classes, whereas woodpeckers and creepers tended

134
to prefer dominant trees with diameter-classes reflecting

stand age; sapsuckers used subordinate trees the most, followed by dominant trees, and thus foraged on smaller trees,

on average, than did woodpeckers and creepers. Chickadees

concentrated on foliage, sapsuckers on live wood (sap), hairy

woodpeckers on dead wood and bark, and creepers on bark.

Foraging behavior mostly was consistent across the stand ageclasses. Pileated woodpeckers were seen rarely in young and

mature stands (4 of 42 observations). Pileated woodpeckers

were observed foraging on fallen trees more (15 percent), a

greater variety of trees, more on snags, and mom on trees

more than 100 cm in d.b.h. in old growth than in young or

mature stands. Hairy woodpeckers used branches on trees

more in old growth than in younger stands (42 percent bole

use in old growth versus 84 percent and 73 percent in mature

and young stands, respectively). Hairy woodpeckers used

more live trees in poor condition and slightly decayed trees

in mature and old-growth stands than they did in young

stands. They also foraged more on large trees in old-growth

than in young and mature stands; trees 20 to 49 cm in d.b.h.

were used the most in young and mature stands. Only three

red-breasted sapsuckers were observed foraging in young

stands. Red-breasted nuthatches tended to use the lower canopy more as stand age increased (percentage of use = 0,8,

and 12 in young, mature, and old-growth stands) and increased their use of very large trees. In young stands, nuthatches selected trees greater than 50 cm in d.b.h. over trees

20 to 49 cm in d.b.h. But in mature stands, they selected for

the 20- to 49-cm diameter-class. Use of diameter-classes by

chickadees reflected availability. Nuthatches foraged more

on dead wood in young stands (27 percent) than in mature

(0 percent) or old-growth stands (6 percent).

Discussion

Forest Development

The Douglas-fir-dominated forests of the southern Oregon

Coast Range displayed a clear pattern of development over

the range of ages we studied: 40 to 525 years. Both the distribution of diameter at breast height in live trees (table 1) and

the patterns of abundance of snags (fig. 3) provide good

models of forest development: attainment of dominance by

some trees, suppression of subordinate trees, and the opening

of the canopy through death of dominant trees. Young stands

were characterized by high densities of l0- to 49-cm d.b.h.

Douglas-firs (table 1); high stocking rates had resulted in

mortality from suppression that produced high densities of

small- and medium-diameter snags (table 2, fig. 3). Relatively

large numbers of well-decayed large snags from the previous

stand were carried over into the young and mature stands.

Young stands were even-aged, had low values for coniferous

foliage-height diversity (fig. 2), and high values of canopy

cover, Midstory and understory layers were undeveloped.

Mortality from competition (suppression) continued into the

mature age-class, which also tended to be even-aged and to

have a low foliage-height diversity. Canopy cover decreased

with age, but mortality in the mature stands began to produce

snags of the size and condition favored by cavity-nesting

birds (moderately decayed snags >50-cm d.b.h.; Cline and

others 1980, Nelson 1989). Mature stands were approaching

a phase of rapid development, including increases in tree

size, abundance of large snags, and vertical stratification of

the canopy.

Tree size (fig. 1) and foliage-height diversity (fig. 2) continued to increase with age through the oldest stands studied.

Mortality rates of dominant trees slowed; however, the

slightly to moderately decayed snags most used by cavityusing birds (mean diameter of snags used for nesting was

94 cm, Nelson 1989) occurred in much lower densities in

old growth than the smaller snags did in the younger stands

(fig. 3). Tree death in young and mature stands is usually due

to suppression, but tree death in old growth is usually due to

butt rot, windthrow, or fire (Franklin and others 1987). Canopy cover was at a minimum, and midstory and understory

development at a maximum, in old-growth stands. Because

of the wildfire history of the Coast Range, 500 years is about

the maximum age of old-growth stands there (Juday 1976);

500 years is also the time of peak accumulation of coarse

woody debris, including snags (Spies and others 1988). The

structure of the old-growth (200-525 years old) forests differs

significantly from young and mature forests. Attendant to

these structural differences are compositional differences in

the makeup of the overstory, the development of a shadetolerant midstory and understory, and, depending on moisture

conditions, a greater development of shrub and forest-floor

vegetation.

Bird Communities

Bird communities in the southern Coast Range were dominated by eight common species (table 3); no marked differences were observed in community structure (figs. 5,6)

among young, mature, and old-growth forests. Total abundance of birds was about equal among age-classes. Species

diversity, as measured by richness, Margalef’s index, and the

Berger-Parker index, did not differ in a biologically significant way among age-classes, although mature stands seemed

to support a slightly less rich and less abundant bird community. All three age-classes were closed-canopied, maturing

coniferous forest; all the study stands were in landscapes

dominated by forest communities.

Forty percent of the bird species present in spring communities were migrants and, of these, only the Vaux’s swift (a

cavity nester) and the olive-sided flycatcher showed an association with old growth. About one-fourth of the resident

135
birds were cavity users; all showed an association with old

growth; and, in addition, the marbled mm-relet and the/winter

wren increased in abundance with stand age. I

Bird communities in old growth differed from those in young

and mature stands, primarily in the abundance and diversity

of cavity-using birds (including the crevice-nesting brown

creeper and the sometimes cavity-using spotted owl). This

compositional change in the bird communities was continuous throughout the age gradient studied, with young forests

supporting the fewest cavity users and old-growth forest

supporting the most. The cavity users that were abundant in

young stands, the brown creeper and the chestnut-backed

chickadee, were the only two that made significant use of

well-decayed (class 3) snags for nesting (Nelson 1989). As

carryovers from the old-growth stands preceding the young

and mature stands, these large and very large, well-decayed

snags were equally abundant in the three age-classes studied.

Our findings suggest that given present conditions, cavityusing birds depend on old growth to support the numbers of

birds necessary to ensure viable populations.

Hypotheses Examined

Large trees-Old growth is unique in the number of large,

live trees, and bark-foraging birds showed a strong (r = 0.73)

numerical response to large-tree density in young and mature

stands. Brown creepers, especially, showed a consistent, positive association with large trees throughout the age gradient

and increased in abundance with age, being twice as abundant in old-growth as in young stands. Creepers selected the

dominant trees in each age-class for foraging and concentrated their foraging on the bark on the tree boles. But brown

creepers were abundant birds-even more abundant; in young

stands than many of the species associated with young stands

(tables 6,7). Large, live trees may not be a necessity for

creepers, but they certainly contribute to maintaining large

populations. We conclude that live, old-growth trees are an

important habitat element for bark-foraging birds, particularly brown creepers.

Spatial diversity-We found that canopy cover decreased

and midstory development increased with age, but understory vegetation reflected moisture more than canopy cover.

Bird species responding to ground cover less than 2 m tall

seemed to be responding to the abundance of forbs and berryproducing bushes relative to evergreen shrubs on a wet-to-dry

gradient, rather than to stage of forest development, although

the varied thrush responded to both. We found no clear pattern of increased ground cover with age. Spatial diversity

associated with old growth apparently did not exert a strong

influence on bird communities.

The Value of Old Growth to Birds

Old growth seems especially important to cavity-using birds.

These birds select large snags out of proportion to their availability even in the midst of abundant, small snags (<50-cm

d.b.h.) (Nelson 1989). Mean diameter at breast height of

snags used for nesting was 94 cm-an old-growth diameter.

The bulk of the snags used were of diameters that do not

occur until after at least 80 years of growth.

The other bark foragers were cavity-using birds whose asso- The pileated woodpecker, hairy woodpecker, and redciation with large, live trees may reflect, in part, their associa- breasted sapsucker were rare in young stands and most abuntions with large, dead trees. They did not concentrate their dant in old growth, though not as abundant as the secondary

foraging on the bark on the boles of large, live trees to the cavity users. The home-range size of woodpeckers exceeds

extent creepers did. Indeed, the hairy woodpecker used large

branches on old, live trees as well as the boles. The redour average stand size, however; the average home-range

size of the pileated woodpecker in the Oregon Coast Range

breasted nuthatch used branches more than boles. The pile- is 480 ha (Mellen 1987). Thus, the presence of old-growth

ated woodpecker used snags as well as live trees. And the stands may provide nesting habitat for woodpeckers and

red-breasted sapsucker foraged on a greater variety of species allow them to forage in nearby younger forests to a greater

than the brown creeper did. degree than would be possible without old growth.

Vertical diversity-Old growth had a much greater vertical

diversity of coniferous foliage than young or mature stands

did. But the foliage-foraging species did not respond numerically to the gradients in diversity or stand age. The diversity

of foliage foragers did not increase with increasing foliageheight diversity. Greater foliage-height diversity (and the

attendant diversity of species) of old growth apparently did

not strongly influence the bird communities.

Snags-The abundance and diversity of cavity-using birds

was positively correlated with large snags. Snags used by

cavity-nesting birds began to increase in availability in

mature stands but were abundant only in old-growth stands.

Ten of the 14 species associated with old growth (tables 6,8)

are cavity users. Two, the spotted owl and Vaux’s swift, are

dependent on old growth (Carey 1989). The only cavitynesting species that was abundant in young stands was the

chestnut-backed chickadee, which used well-decayed, large

snags as well as moderately decayed, large snags for nesting.

Large, and especially very large, moderately decayed snags

are of major importance to cavity-using birds. These kinds of

snags may be difficult to maintain in managed stands.

The chestnut-backed chickadee was most abundant in old

growth but also abundant in younger stands. The red-breasted

nuthatch was three times as abundant in old growth as in

young stands but still relatively abundant in young stands.

136 I
These small species prefer large, tall snags (Nelson 1989).

But unlike most other cavity-using birds (Nelson 1989) chickadees nested in large, well-decayed snags. Young stands

developing after harvest of second-growth stands would be

devoid of these large, well-decayed snags. Loss of these

carryovers from old growth would reduce the quality of

young stands as chickadee habitat.

The Vaux’s swift uses large, hollow snags for nesting

(Gabrielson and Jewett 1940). These swifts will forage over

clearcuts, but 56 of the 61 swifts we recorded in the Coast

Range were in old growth. The large, hollow trees used for

roosting and nesting are not commonly found in young or

mature stands (Carey 1989).

The brown creeper, strictly speaking, is not a cavity nester;

rather it builds a nest under loose bark (Ehrlich and others

1988). The heavily furrowed bark of old-growth Douglas-firs

has been postulated as harboring an abundant arthropod

fauna that serves as food for brown creepers (Mariani 1987).

Our data show that brown creepers prefer to forage on the

largest trees available and that creeper abundance increases

with the abundance of large trees. Creepers were abundant in

all age-classes. They preferred large snags for nesting (mean

d.b.h. was 83 cm) and selected the largest snags available;

nest-snag diameter increased with age. Creepers used both

moderately and well-decayed snags more frequently than the

cavity-using birds did (with the exception of the chestnutbacked chickadee).

The only noncavity nester closely tied to old growth was the

olive-sided flycatcher, an aerial insectivore that nests high on

the branches of coniferous trees (Ehrlich and others 1988,

Gabrielson and Jewett 1940). The tall trees and broken canopy of old growth provides a much better foraging environment than the dense, closed-canopy young and mature forests

in the Coast Range.

Western flycatchers, although most abundant in old growth,

were abundant in the other age-classes as well. The varied

thrush was most abundant in mature and old-growth stands,

but relatively abundant in young stands as well. The association with older stands might reflect a subtle influence of canopy openings on ground cover or an influence of tall canopies

on ground moisture.

Little information exists on the inland ecology of marbled

murrelets; Nelson and others (in press) reviewed what is

known about the marbled murrelet in Oregon. Additional

information on the ecology of mm-relets is needed before the

importance of old growth to them can be determined.

We found no evidence that other bird species we studied

found old growth to be a more favorable environment than

young or mature stands. Many species, however, were not

sampled adequately. And we studied the bird communities

only during the spring. We believe our data were sufficient

to conclude that loss of old growth would negatively affect

cavity-using bird populations. We predict that effects would

be severe for woodpeckers, the Vaux’s swift, and the spotted

owl.

Acknowledgments

We thank the field biologists for their care and persistence

in making and recording their observations: P. Christgau,

D. Crannel, B. Fiero, J. Gingerich, L. Havel, L. Jones,

B. Kuntz, K. Nelson, R. Newton, P. Sullivan, J. Whelan, and

W. Wright. Nelson completed her M.S. thesis on the relation

between cavity-using birds and snags as part of this study.

Study sites were selected by T. Spies, B. Bury, and S. Corn.

We thank M.L. Morrison, F.L. Ramsey, and J. Vemer for

their thorough reviews of earlier drafts of this paper. Funding

was provided by the Old-Growth Forest Wildlife Habitat

Program and the Oregon State Office of the Bureau of Land

Management.

This paper is contribution 118 of the Wildlife Habitat Relationships in Western Washington and Oregon Research

Project, Pacific Northwest Research Station, USDA Forest

Service. 

137
Appendix 

Table lO-Mean standardized counts (number per 

stand visit) of birds within 7.5 m of sampling points 

In yooung, mature, and old-growth forests in the 

southern Oregon Coast Range, 1985 

1.00 

.09 

.oo 

.83 

1.31 

.oo 

2.05 

7.11 

ml 

2.14 

.oo 

.89 

6.7 1 

34 

.45 

3.59 

1.22 

11.33 

1.26 

.w 

no 

.ZL 

.04 

.lxl 

.M) 

.75 

:: 

1.25 

1.12 

.oo 

.xl 

.oo 

.w 

.24 

InI 

.w 

.oo 

68 

3.83 

.oo 

1.42 

-17 

10.46 

1.78 

.w 

.w 

6.49 

11.58 

.24 

.41 

1.53 0.81 

.I4 .I2 

.05 .I6 

.21 .O8 

34 39 

.I3 .m 

4.30 4.86 

8.76 12.34 

.oo .OS 

1.06 68 

.04 .nl 

2.40 .72 

7.63 6.44 

.68 .30 

.37 .61 

2.99 1.08 

34 .50 

7.59 8.81 

2.5 .24 

SKI 0.13 

.w 0.02 

.I6 0.04 

.04 0.10 

al 0.03 

.w 0.15 

.26 0.31 

.I7 0.14 

1.05 0.71 

.I8 0.36 

2.98 3.28 

.I7 0.28 

.08 0.00 

.O3 0.W 

.OO 0.01 

.,I 0.4, 

ml 0.09 

.m 0.08 

.m 0.01 

1.47 1.37 

4.91 3.77 

.03 .03 

3.93 3.61 

.co .w 

8.98 2.88 

250 .71 

.w .01 

.03 .OO 

6.40 4.73 

13.97 15.35 

.62 .2s 

.oo .04 

0.76 

.OO 

1.22 

1.45 

.oo 

2.84 

3.60 

.OO 

.oo 

2.60 

.m 

1.02 

4.61 

67 

.I3 

6.05 

1.63 

II.60 

.?a 

1.41 

.05 

.07 

.oo 

.w 

.oo 

-25 

al 

.I5 

-45 

1.42 

sm 

.w 

33 

.m 

.2cl 

.OO 

.73 

5.83 

1.27 

38 

8.86 

.98 

5.85 

8.14 

.17 

-07 

0.82 0.35 

.I4 .20 

.22 .I7 

36 .38 

.OO .03 

4.66 6.08 

4.89 10.95 

.O4 .O2 

.Jo .I0 

1.48 65 

.w .a2 

.27 .I3 

7.50 7.36 

S2 34 

.41 .99 

3.32 .96 

25 1.48 

6.18 8.79 

.ca 06 

.a4 

.w 

.w 

.O5 

.O4 

.w 

.a3 

:E 

.05 

2.91 

.45 

.w 

.I3 

.m 

.m 

.w 

1.04 

4.83 

4.52 

.a3 

7.34 

.15 

5.36 

11.00 

.I6 

.oo 

33 

36 

.oo 

t.5 

.02 

.w 

04 

.23 

62 

.27 

5.75 

A2 

.05 

.46 

.n 

.08 

.04 

1.02 

4.06 

5.14 

.m 

15.17 

.48 

4.85 

12.69 

.24 

.07 

Table 11-Mean standardized counts (number per 

stand vlslt) of birds witbln 75 m of sampling points 

in young, mature, and old-growth forests In the 

southern Oregon Coast Range, 1986 

Species 

Y0Ung Mature Old 

(“Z5) (n = 8, (” = 19) 

138 
Table E-Mean birds-per-area Index (numbers per 40 ha) of birds In young, mature, and 

old-growth forests in the southern Oregon Coast Range, 1985 

Stand age&w 

American mbin 

Band-tailed pigeon 

Black-capped chickad& 

Black-he&d gmsbeake 

Black-throated gray warbler’ 

Blue grousec 

Brown creeper 

Chestnut-backed chickadee 

Common raven 

Dark-eyed junw’ 

Downy woodpecker 

Evening grosbeak’+ 

Golden-crowned kinglet 

Gray jay 

Hairy woodpecker 

Hammond’s flycatcher’ 

Hermit thrush 

Hermit warbler’ 

Hutton’s vi& 

MacCillivray’s warblef 

Mountain quail’ 

Nashville warble? 

Northern flicker 

Northern pygmy-owl 

Olive-sided flycatcher 

Orange-mownd warbler’ 

Pileated woodpecker 

Pine siski# 

Purple finch’ 

Red-breasted nuthatch 

Red-breasted sapsucker 

Red crossbilld 

Ruby-crowned kinglet 

Ruffed gmusd 

Rufous hummingbird 

Rufous-sided towhee 

Song spamwc 

spotted owl 

Steller’s jay 

Swainson’s thrush 

Townsend’s solitaire 

Varied thrush’ 

Warbliog vi& 

Western flycatcher 

Western tanager= 

White-breasted nuthatch 

Wilson’s warbler’ 

Winter men’ 

Yellow-mmped warblef 

Young 

(n = 8)’ 

2.52 

.13 

.oo 

3.65 

9.35 

.23 

14.22 

78.38 

.84 

5.88 

.45 

2.35 

54.09 

1.17 

1.05 

23.80 

3.14 

73.62 

6.89 

.43 

.07 

1.89 

23 

.03 

5:: 

.04 

1.19 

5.82 

2.58 

.62 

.I3 

.oo 

.a0 

6.46 

.I9 

.oQ 

.oo 

1.94 

11.41 

.12 

5.59 

1.26 

48.40 

6.50 

.08 

42.76 

76.71 

2.96 

45 

4 

0 

29 

54 

2 

90 

325 

2 

54 

3: 

248 

19 

22 

107 

37 

463 

41 

2 

1 

11 

5 

1 

3: 

1 

15 

49 

52 

: 

0 

0 

10 

4 

0 

0 

36 

103 

2 

61 

7 

462 

40 

1 

280 

426 

16 

’ More than 10 percent of the detections of these species were of sieging malts. Mean densities qmrted are 

twice the densities of singing males. 

d Mere than 50 percent af aU detections of these species were of flying birds not included in the estimates. 

139 
Table 13-Mean birds-per-area indexes (numbers per 40 ha) of birds in young, mature, 

and old-growth stands in the southern Oregon Coast Range, 1986 

Species 

American robin 

Band-tailed pigeon 

Black-headed gmsbe& 

Black-throated gray warbler’ 

Blue gmuseC 

Brown creeper 

Chesmut-backed chickadee 

Chipping spaIrowc 

common raYen 

Dark-eyed junta’ 

Downy woodpecker 

Evening grosbe& 

Golden-crowned kinglet 

Gray jay 

Hairy woodpecker 

Hammond’s fl~atcherc 

Hermit thrush 

Hermit wublerC 

House wren= 

Hutton’s vired 

MacCillivray’s warble? 

Nashville warblef 

Northern flicker 

Northern pygmy-owl 

Olive-sided flycatcbef 

Orange-crowned warblef 

Pileated woodpecker 

Pine siskind 

Purple finch= 

Red-breasted nuthatch 

Red-breasted sapsucker 

Red crossbill’ 

Rufous hummingbird 

Rufous-sided towhee 

song sp.wrow~ 

Spotted owl 

Steller’s jay 

Swainson’s thrush 

Varied thrush’ 

Warbling virec? 

Western flycatcher 

western tanagef 

Wilson’s warbler’ 

Winter wren’ 

Wrentit 

Yellow-rumped warbler’ 

Young 

(n = 6)n 

MGUl 

- 

1.84 23 

.07 1 

4.15 26 

8.78 48 

.oo 0 

19.09 83 

25.73 105 

.10 1 

.oo 0 

9.64 52 

.oo 0 

3.58 40 

45.75 139 

2.28 26 

.43 5 

32.14 130 

4.60 34 

65.56 369 

.sm 0 

6.44 40 

1.06 6 

1.80 5 

.oo 0 

.m 0 

.11 1 

1.40 9 

.N 0 

1 .oo 11 

2.41 16 

3.69 43 

.18 2 

.07 1 

11.08 12 

.14 1 

1.13 5 

.oo 0 

2.08 27 

29.96 110 

4.15 31 

3.55 27 

40.15 267 

3.74 22 

39.12 162 

46.59 209 

.42 6 

.46 2 L 

Stand age-class 

(n = 8) 

Mean N 

2.10 36 

.53 11 

.83 7 

2.70 20 

.oo 0 

31.47 192 

34.79 200 

.08 1 

.08 1 

5.67 42 

.m 0 

2.01 31 

80.95 335 

1.50 24 

1.27 21 

20.23 113 

.99 10 

34.04 262 

.oo 0 

.lO 1 

.oo 0 

.oo 0 

.22 5 

.12 2 

.oo 0 

.ll 1 

.OR 2 

.13 2 

.A4 4 

6.54 118 

1.34 23 

30 6 

7.42 12 

.21 2 

.oo 0 

.oo 0 

2.65 47 

19.22 123 

17.64 179 

.lO 1 

32.33 301 

.76 6 

38.25 223 

69.91 443 

.46 9 

.oo 0 

_Y 

.74 14 : 

2.21 39 : 

.21 5, 

35.75 515 : 

70.39 957 : 

.09 3 

.37 11 

2.67 47 

.06 3 

.57 21 

64.12 623 

.82 30 

2.16 84 

5.81 77 

3.15 76 

40.11 733 

.23 6 

1.46 28 

1.74 33 

.55 5 

.15 8 

.lO 4 

.29 8 

.85 18 

.43 24 

1.56 57 

1.31 28 

11.52 446 

1.30 

.52 

53 i 

25 

11.76 45 : 

56 13 I 

.57 8h 

.44 6’ 

2.14 89 

16.35 213 

15.60 371 

.46 11 

59.55 1305 

1.02 19 

25.88 358 

63.51 946 

.45 21 

Sl 7: