Olive-Sided Flycatcher in Western North America
I
I OLIVE-SIDED FLYCATCHER I IN WESTERN NORTH AMERICA I Status Review I I I I I I I I
I Preparedby: AvifaunaNorthwest Bob Altman I 18000 SE Vogel Road Boring, Oregon 97009 I Prepared for: U.S. Fish and Wildlife Service I Oregon State Office 2600 SE 98th Avenue, Suite 100 I Portland, Oregon 97266 July 1997 I I I I I I I I I I I I I I I I I I I I I I I SUMMARY
I The olive-sided flycatcher is perhaps the most recognizable of our North American forest flycatchers, yet probably alsothe least known. Its summer domain is the vast coniferous forests spread out over I North America where it occurs from sea level along the Pacific Coast to spruce forest at 3,350 meters in theRocky Mountains. The presence of the olive-sided flycatcher in these forests is announced by the prominent and resounding three-syllable song "Quick, three beers". Once visually located, the I image is that of a somewhat bulkyflycatcher perched erect and motionless at the top of a tall tree or snag except when singing its emphatic song or darting out to capture flying insects.
I Olive-sided flycatcher breeding habitat in western North America is montane and northern coniferous forest. Wrthinthese forests, it occurs primarily 1) within forest bums where snags and tall, residual live trees remain; 2) near water along the wooded shores of streams, lakes, rivers, beaver ponds, I bogs, and muskegs, often where standingdead trees are present; 3) at forest edges near natural (e.g., · · meadows, canyons) or man-made openings in the forest, often at the juxtaposition of late and early . . successional forest; and 4) in natural or man-made open or semi-open forest stands with a low I percentage of canopy cover, rather than in the forest interior or beneath the forest canopy. The presence of prominent trees or snags, which serve as foraging and singing perches, is a common I feature of all nesting habitat. Studieson olive-sided flycatcher naturalhistory and ecology are lacking, and much of our knowledge about the species is anecdotal or incidentally acquired from multi-species projects. It is a I monogamous breeder producing 3-4 eggs per clutch and one clutch per pair per year. Re-nesting after a failedclutch regularly occurs. Nests are open-cup structures placed at varying heights above I the ground and well out from the trunk of a coniferous tree in a cluster of needles and twigs on a horizontal branch. Nest areas are aggressively defended by both members of the pair, and limited banding data suggests strong sitefidelity. Nesting territories are relatively large for a passerine bird, I up to 40-45 ha per pair, but most often in the range of 8-20 ha per pair.
The olive-sided flycatcher preys almost exclusively on flying insects, including bees, wasps, flying I ants, beetles, moths, and dragonflies. It often forages from a high, prominent perch at the top of a snag or the dead tip or uppermost branch of a live tree where it flies out (sallying or hawking) to snatch a flying insect,and then returns to thesame or another prominent perch. Its foraging behavior I as anair -sallying insectivore requires exposed perches and unobstructed air space, thus tall trees or snags and broken canopy provide a better foraging environment than closed canopy forest.
I The olive-sidedflycatcher is a regularly occurring breeding species throughout much of the coniferous forest inwestern North America, although data indicate declining populations in most of these same areas. Populationtrends basedon BreedingBird Survey data show highly significant declines for all I continental (North America), national{United States and Canada), and regional (eastern and western North America) analyses, and for most state and physiographic region analyses. Two salient characteristicsof the declines are: 1) declines are greatest in the core of the species range (i.e., where I the species has its highest abundance), and 2) the rate of decline is increasing in the last 15 years. I I I
Despite the magnitude and pervasiveness of population declines, protection through regulatory status I is lacking. This may be due to the fact that 1) it is a widespread species that occurs in an abundant and widespread habitat type (conifer forest), unlike many declining species that have limited ranges and/or occur in discrete patches of declining habitat (e.g., wetland or grassland associated bird I species); 2) it is highly detectable due to its conspicuous song and perching habits, and its high level of vocal detectabilityat relativelylarge distances ensures recognition where it is present; and 3) it has always been thinly distributed due to its relatively large territory size, thus declines may not be as I apparent to the casual observer.
Several factors have been suggested as contributing to the population declines. Initial speculation I has focused on habitat alteration/loss on the wintering grounds based on the relative consistency of population declines throughout the breeding range of the species. The principal wintering range of the olive-sided flycatcher is Panama and the Andes Mountains of north and western-South A.riterica I from northwestern Venezuela south through Ecuador to southeastern Peru and northern Bolivia. Wintering habitat is generally similar to that on the breeding grounds - forest edge and forest
· · openings, especially where scattered tall trees or snags are present. It occurs. primarily in mature _ . evergreen forest, particularlylow- to-mid elevation (500-2,000 meters) montane forest. The low-to- mid elevation montane forests of the Andes Mountains have been deforested more extensively than most other forest types in the neotropics, and are considered to be of high conservation concern for nearctic migrants in South America. Inter-Andeanvalleys are almost completely deforested, and 85 percent of the montane forests have been altered.
The population declinesexperienced by the olive-sided flycatcher may also be due to various factors on the breeding grounds. These include habitat loss through conversion to non-forest and younger I successional stages, alteration of habitat from forest management practices (e.g., clearcutting, fire suppression), availability and acquisition of food resources, and reproductive impacts from nest predation or parasitism. During the past 50 years, forest management on the breeding grounds has I resulted in anincrease in forest openings and edge habitat which has seemingly increased habitat for the olive-sided flycatcher. However, there is speculation that this dichotomy of increased habitat availability and declining populations may indicate that the occurrence of the olive-sided flycatcher I in harvestedforest represents an "ecological trap". Inthis scenario, the habitat may appear suitable, but success in terms of reproduction and/or survival is poor due to factors such as limited food resources, predation, or parasitism. I
It has also been speculatedthat the olive-sided flycatcher may have e:volved to depend on early post I firehabitat, andit has likely been negatively affected by fire-control policies of the past 50-100 years. The ability of forest management practices thatcreate forest openings and edge habitat (e.g., selective cutting, clearcutting) to mimic natural disturbanceregimes caused by forest fires has been questioned. I Habitat created by these types of forest management may provide only the appearance of early post fire habitat, but be lacking in some attributes or resources required by olive-sided flycatchers. I The effect of habitat loss/alteration on declining olive-sided flycatcher populations may be exacerbated by three factors related to the speciesbiology: 1) individual birds/pairs require large areas of habitat on both the breeding and wintering grounds; 2) it has a high potential for sensitivity to I habitat alteration due to foragingspecialization; and 3) there are indications that it may exhibit strong I I I
I site fidelity on both the breeding and wintering grounds, which fuay make it less adaptable to habitat loss. It also has the greatest migration distance among the 32 species of North American flycatchers; thus, is highly vulnerable for an extended period (1-2 months) to all adverse factors associated with I migration (e.g., habitat loss, predation, availability of food resources).
Data are unavailable to correlate breeding and wintering locations of a specific population, which I precludes our ability to assess the relative importance of changes in wintering and breeding habitats on local or regional populations. For example, some olive-sided flycatcher populations may be relatively unaffectedby forest management practices on the breeding grounds, but these populations I may winter in areas where tropical deforestation has been particularly extensive. At this time, only generalrange-wide factorsin wintering habitats (i.e., tropical deforestation) have been implicated as contributing to declines in the species population. However, examples from other declining species I wintering in the same forests indicate that some problems may also be occurring on the breeding grounds. Thus, conservation efforts for the olive-sided flycatcher may require not only preservation I of montane tropical forests in Andean South America, but also protection of breeding habitat throughout North America. ..
I Development of management and conservation strategies for the olive-sided flycatcher is hampered by a lack of natural history information on the species, and an absence of knowledge of factors adversely affecting the species. Until these types of data are available, management strategies are I speculative, and dependent on circumstantial evidence which suggests that suitable breeding habitat can be createdthrough forest management or natural fires. However, it must be recognized that these recommendations aretentative andshould be adaptive due to the absence of knowledge of the olive I sided flycatcher population viability in these habitats, particularly since population trends continue to show declines.
I Given the magnitude, spatial consistency, and increasing rate of declines in olive-sided flycatcher populations, it is imperative that species-specific research be conducted to assess the viability of populations within natural and human-altered habitats, and to examine and identify causative factors II in the population declines. To meet current data gaps, research is needed in two general areas: 1) breeding season productivity and associated environmental attributes across various habitats, landscapes, and forest management regimes; and 2) evaluation of the speciesstatus and ecology on I the wintering grounds, including the effect of forest alteration on wintering populations.
I ACKNOWLEDGEMENTS
I Financial support was provided by the U.S. Fish and Wildlife Service, Oregon State Office, and Gary Miller served as the project liaison. Jim Lowe provided data from the Cornell Laboratory of Ornithology's Nest Record Program. Julie Fulkerson prepared the cover drawing. Brad Andres, I Cathy Brown, Paul Cotter, Jeff Dillion, Sallie Hejl, Tasha Kotliar, Bruce Petetjohn, and Rex Sallabanks reviewed the draft report. I am especially grateful to John Wright for providing unpublished dataand a critical review of the draft, and to Bruce McCullough and Lori Hennings for I extensive input on olive-sided flycatcher breeding biology based on a season of field work. I I
I I TABLE OF CONTENTS Page I SUl\fMARY ACK NOWLEDGEMENTS INTRODUCTION...... 1 I PURPOSE AND NEED...... 1 TAXONOMY...... 2 DESCRIPTION...... 3 I Appearance...... 3 Voice...... 3 GEOGRAPIDC DISTRIBUTION...... 4 I Winter ...... :...... 4- Breeding Season...... 4 Migration...... 4 I NATURAL IDSTORY...... 7 Breeding Biology...... ··...... 7 Courtship/Pairing...... 7 I Nesting...... 7 Territory...... 10 Perch Trees...... 11 I Foraging and Food Habits...... 11 Foraging Methods...... 11 I Prey...... 11 Foraging Locations ...... 12 Site Fidelity...... 12 I Migration Phenology ...... 13 Departure from Wintering Grounds...... 13 Spring Migration and Arrival on the Breeding Grounds...... 13 I Departure from Breeding Grounds...... 13 Fall Migration and Arrival on the Wmtering Grounds ...... 14 HABITAT ASSOCIATIONS...... 14 I Winter ...... 14 Breeding Season...... 15 Migration...... 19 I POPULATIONS ...... ·...... 20 Monitoring...... 20 Trends...... 22 I Abundance/Density...... 31 THREATS AND LIMITING FACTORS...... 32 Winter ...... 32 I Breeding Season ...... ,...... 34 Habitat Loss...... 34 Forest Management...... 34 I Foragingand Food Resources ...... 36 I I I
Predation...... 36 I Nest Parasitism...... 36 Nest Competition...... 37 Migration...... 3 7 I Other Natural or Man-Made Factors...... 37 Pesticides...... 37 Forest Health...... 3 7 I Inadequacy of Existing Regulatory Mechanisms...... 37
CONSERVATION AND MANAGEMENT...... 38 RESEARCH AND MONITORING NEEDS...... 40 I LITERATURE CITED ...... 42 APPENDIX A I
LIST OF TABLES ·I
Table 1. Breeding Bird Survey regional and continental population trend estimates for the I olive-sided flycatcher, 1966-1996...... 23 Table 2. Breeding Bird Survey physiographic regions population trend estimates for the I olive-sided flycatcher, 1966-1996...... 25 Table 3. Breeding Bird Survey state/province population trend estimates for the olive- sided flycatcher, 1966-1996 ...... 27 I Table 4. Natural Heritage Program ranks and state/province listing status for breeding 39 populations of the olive-sided flycatcher in western North America...... I
LIST OF FIGURES I
Figure 1. Breeding distribution of the olive-sided flycatcher in North America...... 5 I
Figure 2. Reported winter occurrences of the olive-sided flycatcher in South America...... 6 Figure 3. Olive-sided flycatcher annual population trend estimates_ based on Breeding Bird Survey data...... 29 I Figure 4. Olive-sided flycatcher relative abundance indices on Breeding Bird Survey routes...... 30 I I I I I I
I INTRODUCTION
This report summarizes the status of the olive-sided flycatcher ( Contopus borealis) in western I North America from the eastern edge of the species' breeding range in western Texas and eastern New Mexico, Colorado, Wyoming, and Montana, north to eastern Manitoba and northern I Minnesota. Coniferous forests within this area represent the core of olive-side flycatcher abundance in North America. Although the focus of this report is western North America, information on olive-sided flycatcher natural history and populations in eastern North America is I presented where appropriate. A summary of the biology, status, and management of the olive sided flycatcher in the northeastern United States is presented in Peterson and Fichtel (1992). I Additionally, numerous state and provincial Breeding Bird Atlas species accoun.ts from eastern North America provide specific information on distribution and natural history of the species I within those areas. I PURPOSE AND NEED
The olive-sided flycatcher was previously listed as a Federal Candidate (Category 2) species (U.S. I Department of Interior 1994) prior to discontinuance of the Category 2 list (U.S. Department of the Interior 1996). It is currently listed as a Species of Management Concern by the Office of Migratory Bird Management in each of the seven regions of the U.S. Fish and Wildlife Service
I (USFWS) (USFWS 1995) . In western North America, it is a state listed "species of concern" in Alaska and California. It also has been designated as a sensitive species by the U.S. Forest I Service (USFS) in the Rocky Mountain Region (Region 2) (Finch 1992), and a species associated with old-growth forests in the Oregon Coast Range and Cascade Range (Ruggerio et al. 1991). The need for a status review is directed in Objective 2, Strategy 2, Task 2.1 of Nongame Bird I Strategies (USFWS 1988), which calls for preparation of regional status reports for species listed as nongame "species of management concern". I Concern regarding the status of the olive-sided flycatcher is based on documentation of population declines throughout the species range (Robbins et al. 1989, Peterjohn and Sauer 1994). I Population trends based on Breeding Bird Survey (BBS) data for the period 1966-1996 show highly significant declines for all continental, national, and regional analyses, and for most state I and physiographic region analyses. Several researchers have presented information that supports concern about declining population I trends of the olive-sided flycatcher. Hejl (1994) reported that the olive-sided flycatcher had the highest rate of decline (3.5 percent) among coniferous forest bird species between 1968-1991 I based on BBS data. Reed (1995) listed olive-sided flycatcher as the species most vulnerable to I 1 I I extirpation among 74 montane breeding bird species in the Great Basin region based on seven I biological variables: geographic range, population size, reproductive potential, susceptibility to cowbird parasitism, migratory status, and diet specialization. In a conservation assessment for landbirds in the Interior Columbia River Basin, olive-sided flycatcher was one of 15 species of I highest management concern (Saab and Rich in press). Petit et al. (1993) listed the olive-sided flycatcher as one of the 12 most highly vulnerable species to alteration of tropical forests. Stotz I et al. ( 1996) rated it as a high priority species for breeding season research in Baja California because it is so poorly known. I Recent prioritization of species as part of the Partners in Flight Neotropical Migratory Bird Conservation Programfurther indicates concern regarding the olive-sided flycatcher. Among 90 li species on the1996 NationalWatch List, olive-sided flycatcher was ranked as a moderate priority species (Carteret al. 1996). It has also been designated as a priority species for conservation in nearly every western state(Terry Rich, Partners In Flight WesternWorking Group chairperson, ·I pers. comm.).
Studies on the natural historyand ecology of the olive-sided flycatcher are lacking, such as those I available for other North American forest flycatchers including Hammond's (Empidonax hammondii) (Davis 1954, Johnson 1965a, Mannan 1984, Sakai 1988), dusky (Empidonax I oberholsen) (Sedgwick 1993), and western flycatcher (Empidonax di.fficilis) (Davis et al. 1963, Sakai 1988). Most of our knowledge about olive-side flycatcher natural history is anecdotal or incidentally acquired from multi-species projects. The only two studies on the olive-sided I flycatcher is a recentproject in Alaska which evaluated phenology and rate of singing, habitat use, and breeding biology (Wright 1997), and an ongoing project in theCascade Mountains of northern Oregon which is examining nesting success, breeding biology, and habitat area requirements I (Altman in prep.). The limited natural history information precludes opportunities for setting population and habitat objectives, the two principal parameters being used to develop landbird I conservation strategies (Mueller 1993, Bonney and Pashley 1994). I TAXONOMY I The first olive-sided flycatcher specimen was taken in Saskatchewan near Carlton along the Saskatchewan River and described as Tyrannus borealis (Swainson and Richardson 1832). Later generic changes included the monotypic genus Nuttallomis in 1887 (Ridgway 1887), and the I change to Contopus in 1983 (American Ornithologist's Union 1983). The specific name mesoleucus replaced borealis for several years (American Ornithologist's Union 1931) based on I Cory and Hellmayr (1927), but further analysis (van Rossem 1934) resulted in reinstatement of borealis as the specific name (American Ornithologist's Union 1945). I 2 I I I
I Banks and Browning (1995) suggest a change to Contopus cooperi because it was the earliest valid name for olive-side flycatcher. They note that the use of this name in Nuttall's "1832" manual, which was available for sale in December 1831, predates part 2 of Swainson and Richardson's I "Fauna Boreali-Americana" which was published in February 1832.
I Despite occurring over the entire continent of North America, the olive-sided flycatcher does not vary subspecifically. Recognition of an eastern and western subspecies was first proposed by Bangs and Penard (1921), and several authors have used majomis, borealis, or cooperi as I subspecific names (Banks and Browning 1995). Most recent authors recognize the olive-sided flycatcher as a monotypic species with the western birds slightly larger than eastern birds. It is I most closely related to the eastern wood-pewee ( Contopus virens) and the weste� wood-pewee (Contopus sordidulous) (Zink and Johnson 1984). I DESCRIPTION
I Appearance. The olive-sided flycatcher is generally characterized as a relatively large, stoutly built, large-headed, short-necked flycatcher with a relatively short tail and an erect posture. It is I distinguishedfrom other forest flycatchers by larger size, proportionately shorter tail, and white patches onboth sides of rump which show most prominently in flight. The overall adult plumage color is olive-gray (darkest on crown) with a narrow whitish stripe down the breast and belly I giving the appearance of an unbuttoned vest. Both sexes are similar in plumage, but males have longer wings (Pyle et al. 1987). Juvenal plumage is similar to the adult, but darker above and I brighter below (Bent 1942) with buffy or brownish tipped wing coverts (Jewett et al. 1953).
Voice. The song of the olive-sided flycatcher is its most characteristic feature. It is a I distinctively loud and penetrating three-note whistle with the middle note being the highest and often referred to as the mnemonic Quick, three beers (Taverner 1928, Peterson 1980). There have been numerous other descriptions including Come righthere (Godfrey 1986), Look, three deer I (Terres 1987), whut-whee! tew (Jewett et al. 1953), or a spirited whistle I say' there (Peterson 1990). I The call is three evenly spaced trebled notes often referred to as pip, pip, pip (Peterson 1980, Godfrey 1986), although two-note "piping" is frequently heard (Altman in prep.). The 'piping" I call is frequently used as a contact vocalization by both sexes including calling by females while sitting on the nest (Altman in prep.). It is also used by both sexes as an alarm call near the nest I (Bent 1942, Terres 1987) where the frequency and intensity of the "piping" is increased (Altman in prep.). I I 3 I I
The male's emphatic song is usually given from the top of a tree or snag, often the tallest in the I area, where it can carry great distances due to the strength of the song and lack of absorption from vegetation (Ehrlich et al. 1988). The olive-sided flycatcher is a prodigious singer, often being the first bird heard in the morning, and the last one at night (Grinnell and Storer 1924, Bent 1942)". I Singing has also been noted after dark on bright moonlight nights (Roberts 1932). I The song is occasionally heard in the non-breeding season, particularly in spring migration (Ridgely and Gwynne 1989, Ridgely and Tudor 1994). Phillips et al. (1964) even heard the territorial song in December in Mexico. Thethree-note callisfrequently heard in winter (Ridgely I and Tudor 1994). I GEOGRAPHIC DISTRIBUTION 'I Winter. The principal wintering range of the olive-sided flycatcher is Panama and the Arides · · Mountains of north and western South America, from northwestern Venezuela south through Ecuadorto southeastern Peru and northernBolivia (Fitzpatrick 1980, DeGraaf and Rappole 1995) I (Figure 1). It is one of 13 boreal landbirds that winter almost exclusively in South America (Erskine 1977). The olive-sided flycatcher is most abundant in lightly forested areas and edges I of the Andean Range of Columbia. Elsewhere in South America, it has been reported from southwesternBrazil (Willis et al. 1993), the Guianas (Paynter 1995), and in Trinidad offthe coast of northeastern Venezuela (ffrench 1991). Occasional wintering birds occur north into Central I America including Costa Rica (Stiles 1980, Blake and Loiselle 1992), Belize (Russell 1964), Guatemala (Land 1970), and Mexico (Phillips et al. 1964). There are some accidental winter records from southern California (Grinnell and Miller 1944, Garrett and Dunn 1981, Hamilton I and Willick 1996), including the same individual returning for six consecutive years (1984-1990) to Hope Ranch in Santa Barbara (Lehman 1994). I
Breeding Season. The olive-sided flycatcher breeds only in North America (Figure 2). In westernNorth America, the breeding range extends south from near tree line in boreal Alaska and I Canada including western and central Alaska and central Yukon, and eastward through Canada to northcentral Manitoba. It extends south in the Rocky Mountains to the higher elevations of I easternArizona, western New Mexico, and western Texas, and in the Sierra Nevada Mountains south to northern Baja California. \I Migration. The principal migratory route of the olive-sided flycatcher is throughout the forests of western North America, Mexico, and Central America (Bent 1942, Gabrielson and Lincoln 1959). It is an uncommonmigrant through the midwestern United States, and a rare transient in I the southeastern United States (Imhof1976), includingFlorida (Sprunt 1954, Duncan 1988). The I 4 I I I Figure 1. Reported winter occurrences ofthe olive-sided flycatcher in South America (from Paynter 1995). I I I I /I
I I I I
';.i ·I / I I
I I . i -·· UUo�Jrr-..-.. -r--· t��- I .; \·· 111111111111 \ f .· I •1. . L \
· \ 'F---,' --··-- i-- -···- \I 'I 1 I �I - ,1· I --" I . '"'/\�"' \ , � \ . J . -- .•I _ - _J_-- I
Figure 2. Breeding distribution ofthe olive-sided flycatcher in North America (from Peterson and Fichtel 1992). J I I
I Florida records and othersalong the Gulf Coast of Alabama (Imhof 1976) include both spring and fall migrants, suggesting a few individuals may make the trans-Gulf of Mexico flight to Central I America. InCentral America, the olive-sided flycatcher is considered a common fall and spring migrant in Costa Rica (Stiles 1980), but an uncommon transient in Honduras (Monroe 1968), Guatemala (Land 1970), and Panama (Ridgely 1976). Unusual migrant records include transients I in the southern Caribbean Islands of Trinidad/Tobago and Bonaire (ffrench 1991, Arendt 1992).
I NATURALHISTORY
I Despite its well known song and high level of detectability, there is a lack of natural history information on the olive-sided flycatcher. Forexample, Murphy (1983a) summarized nesting data on open-nesting tyrant flycatchers breeding in North America, but did not include olive-sided I flycatcher because of a lack of quantitative data for the species.
I Breeding Biology
Counship/Pa iring. The olive-sided flycatcher is considered a monogamous breeder with one I clutch per pairper year (Harrison 1975), although suspected polygyny has been observed (Wright 1997). Single instances of polygynybeen have documented for eastern and western wood-pewees (Eckhardt 1976), congeners of the olive-sided flycatcher. The pre-nesting period of territory I establishment and attraction of mate may last up to two weeks (Bent 1942). It is characterized by aggressive defense of the territoryfrom intruding males and active pursuit of the female. I Nesting. Nests have been reported from near sea-level in Berkeley California (Dixon 1920) to 2,900 meters in Colorado (Bailey and Niedrach 1965). Nests are shallow, open-cup structures I made of twigs, bark strips, and dry grass lined with lichens, moss, and fine grass and rootlets (Taverner 1928, Bent1942, Salt and Salt 1976). Nests are often placed high in the tree and well I out from the tree trunk in a cluster of needles and twigs on a horizontal branch (Harrison 197 5, DeGraaf and Rappole 1995). Nest placement high in the tree and closer to the foliage thanthe trunk hasshown been to be an important strategy forincreasing nest success in another flycatcher, I eastern kingbird (Tyrannus tyrannus) (Murphy 1983a). Nest ·construction is believed to be primarily if nottotally by the female (Wright 1997). Most nests arein coniferous trees, although nests have beenreported from tremblingaspen (Populus tremuloides) in southern British Columbia I (Cannings et al. 1987); black oak (Quercus velutina), sycamore (Prosopis sp.), and Fremont cottonwood (Populus fremontl) in southern California; Gambel' s oak (Quercus gambellil) near I Flagstaff, Arizona (Phillips 1936), and alder (Alnus sp.) and gold-leaved oak (Quercus chrysolepis) in northernCalifornia (Smith 1927). Atypical nest sites include two nests on building I ledges in Colorado and Arizona (Jim Lowe, Cornell Nest Record Card Program, pers. comm.). I 7 I I
Most reports on olive-sided flycatchernests have not included a description of position of the nest I treerelative to the foreststand or forest opening. Nests have been reported in forest burns (Hutto 1995a), in unburned patches within forest burns (Edwards 1973), at forest edge (Bendire 1895, Dixon 1920, Phillips 1936, Altman in prep.), in open, regenerating forests with older leave trees I (Altman in prep.), and in dense stands of trees (Wright 1997). I Nest heightis variable, but often at a considerable height above ground. The highest nests occur in the western mountain ranges of the United States, and nest heights are generally lower in the northern boreal forest including Canada and Alaska. Smith (1927) summarized information on I nest height and other attributes for the less than 10 nests reported in the literature at that time. I The range of nearly all reported nest heights in western North America is 1.5 to 25 meters. An exception is an unmonitored nest reported to be nearly 60 meters in a fir tree near Lake Tahoe in the Sierra Nevada Mountains (Head 1903). Some of the highest reported nests include 24 meters ,, ·t in western hemlock and 23 meters in Douglas-frr (Pseudotsuga menziesiz) iri the Cascade Mountains (Altman in prep.), and two nests at 22 meters in a silver fir (Abies alba) and a Douglas-fir in the Sierra Nevada Mountains (Barlow 1901). The highest monitored nest was 25 I meters in a white fir (Abies concolor) in Arizona (Eric Reimer, University of Montana, pers. comm.). Nests have been reported as low as 1.5 meters in a redwood (Sequoia sempervirens) in I northern California (Bent 1942); 2.1 meters in western hemlock and noble frr (Abies procera) in northern Oregon (Altman in prep.); 2.4 meters in a spruce (Picea sp.) in central Oregon (Gabrielson and Jewett 1970); 3.0 meters in Gambel's oak in Arizona (Phillips 1936), black I spruce (Picea mariana) in Minnesota (Roberts 1932), tamarack (Larixlaricina) in central Alaska (Wright 1997); and westernhem lockand noble firin northernOregon; and 3.1 meters in Douglas I fir in southern British Columbia (Cannings et al. 1987).
Some studies have reported on the range of nest heights where several nests have been located. I Meanheight of five nests in an interior Douglas-fir forest of west-central Idaho was 14.8 meters, with a range of 9.1 to 19.8 meters. (Medin 1985a). Mean height of six nests (five in Douglas-frr and one in trembling aspen) in British Columbia was 7 meters, with a range of 3.1 to 12.3 meters I (Cannings et al. 1987). Mean height of 19 nests in central Alaska (15 in black spruce, one in white spruce [Picea glauca], and one in tamarack) was 6.4 meters, With a range of 3 to 12 meters. I Mean height of 50 nests in the Cascade Mountains of northern Oregon (21 in western hemlock [Tsuga heterophylla], 14 in noble fir, six in grand fir [Abies grandis], five in Douglas-fir, and three in mountainhemlock [Tsuga mertensiana]) was 9.1 meters, with a range of 2.1 to 24 meters I (Altman in prep.). I Outch initiation is dependent to a great degree on latitude and elevation. The range of egg dates for western North America as listed by Bent (1942) is May 20 to July 4 in California, and June I 8 I I I
I 16 to July 20 in Colorado. In the Okanogan Valley of southern British Columbia, the earliest recorded clutch is May 22 and the latest is June 21 (Cannings et al. 1987). In western I Washington, nests with eggs were found from June 8 to July 14 (Jewett et al. 1953). In the Cascade Mountains of northernOregon, nests with eggs were found as early as June 6 and as late as July 29 (Altman in prep.). In central Alaska, initiation of first clutches for 11 nests ranged I from May 31 to June 15 (Wright 1997) At a recently monitored nest in Arizona, clutch initiation was June 11 (EricReimer, BBIRD, University of Montana, pers. comm.). Mean laying date from 68 samples of museum egg sets from throughout the species range was June 22 (Murphy 1989). I Among the 32 species of North American breeding flycatchers, this mean laying date was exceeded by only three species, willow flycatcher (Empidonax trailliz), gray flycatcher I (Empidonax wrightiz), and sulphur-bellied flycatcher (Myiodynastes luteiventris)..
Clutch size is typically three eggs (Bent 1942, Harrison 1975), but nests with four eggs are not I. unusual (Barlow 1901, Dixon 1920, Wright 1997), and a nest with five eggs has been reported in Oregon (Gabrielson and Jewett 1970). However, in the Cascade Mountains of nortlietn I Oregon, four-egg (n=l l) and three-egg (n=l l) clutches were equally common (Altman in prep.). Mean clutch sizefrom 68 samplesof museum egg sets fromthroughout the species rangewas 3.02 I eggs (Murphy 1989). The incubation period has been variously reported as two weeks (Burns 1915, Gabrielson and Lincoln 1959), 15-19 days (Petersonand Fichtel 1992), and 16-17 days (Harrison 1975, Godfrey I 1986). The incubation period for 10 nests in central Alaska was 14-16 days (Wright 1997). In the Cascade Mountains of northern Oregon, incubation period ranged from 13-16 days (Altman I in prep.). Incubation is performed solely by female (Harrison 1975, Ehrlich et al. 1988).
The nestling period has been variously reported as 15-19 days (Peterson and Fichtel 1992), 16 I days (Harrison 1975), and about three weeks (Bent 1942). The nestling period at eight nests in central Alaska was approximately 15-19 days (Wright 1997). In the Cascade Mountains of I northern Oregon, the nestling period ranged from 17-21 days, but most were in the 19-21 day range (Altman in prep.). The young are altricial and both parents attend and feed the young, I which are brought insects in the bill (Bent 1942, Harrison 1975, Wright 1997). Fledgling olive-sidedflycatchers are dependentupon theparents after leaving the nest. They have been observed with the adults near the nest up to 17 days after fledging (Wright 1997), and may I remainas a family group until fall migration (Mearns 1890). Mearns (1890) also suggested that adults and young nesting in higher elevations move down slope after the breeding season. I Fledglings have been reportedto weakly vocalize the familiar three syllable song on their frrst day out of the nest (Head 1903, Altman in prep.). I I 9 I I
Olive-sided flycatchers will re-nest if the first nest fails, although only a single brood is raised per I year. In central Alaska, three knowninstances of re-nesting were observed including a successful re-nesting 300 meters away (Wright 1997). In the Cascade Mountains of northern Oregon, six re-nests were documented including two double re-nests (Altman in prep.). All of the re-nests I were within 200 meters of the previous nest, and the closest was 60 meters. Harrison ( 197 5) also reported on a double re-nesting in Maine. The original nest had been destroyed on June 28, but I the same female built a new nest and had three eggs 12 days later. This nest was also destroyed and 16 days later the same female had built another new nest and was incubating 3 eggs. I Territory. Males begin singing to establish a territory and attract a mate upon arrival on the breeding grounds. The nest area is aggressively defended by both members of the .pair, including I attacks upon human intruders (Bendire 1895, Jenks 1934, Jewett et al. 1953, Altman in prep.), and other bird or predator species approaching the nest (Barlow 1901, Salt and Salt 1976, Terres 1987). Ligon (1961) noted that the olive-sided flycatcher was intolerant of the Steller's Jay ·a (Cyanodtta stelleri), a potential nest predator. Adult olive-sided flycatchers have also been reported to be aggressive towards gray jays (Perisoreus canadensis) and red squirrels (Tamiasdurus hudsonicus) approaching the nest (Wright 1997). I
Nesting pairs are generally well-spaced and require a relatively large territory. Bent (1942) I estimated one pair of olive-sided flycatchersper 1. 6 km of shoreline along Lake Washington near Seattle at theturn of the century. Bendire (1895) noted the area occupied by a pair was rarely less than 0.8 km in extent. Reported estimates of olive-sided flycatcher densities were compiled from I numerous sources to examine territory size in different forest types and regions (Appendix A). Estimates of territory size vary, although most were in the 8-20 ha range. Some of the larger I territory sizes have been reported in the Sierra Nevada Mountains; 45 ha in pine forest (Bock and Lynch 1970), 40 ha in mixed conifer forest (Raphael et al. 1987), and 25 ha in sequoia forest (Marshall 1988). Mean size of 17 territories in central Alaska was 17.9 ha, with a range of 9. 7 I to 26.4 ha (Wright 1997).
In a recent study in central Alaska, territory configuration and proximity to other olive-sided I flycatchers was associated with landscape features (Wright 1997). Olive-sided flycatchers did not saturate a block of forest with territories abutting on most sides; but commonly used drainages I where territories were not in direct contact with another olive-sided flycatcher territory, or only abutted with another territory on one side. I In the Cascade Mountains of northern Oregon, olive-sided flycatcher territories within regenerating harvest units were often separated by stands of mature trees, although two nests I within a large shelterwood cut were only 450 meters apart (Altman in prep.). The closest nests from different pairs were 200 meters apart, although separated by a narrow stand of mature forest. I
10 I I I
I Unlike many Nearctic migrantsthat occur in mixed flocks in winter, the olive-sided flycatcher is generally solitary and territorial (Stiles and Skutch 1989, Ridgely and Tudor 1994). In northern I Columbia, where it was the most common non-parulid migrant species, the olive-sided flycatcher was part of a mixed species flock for only two percent of the observations (Johnson 1980). A close congener, eastern wood-pewee, has also been reported to be territorial on their wintering I grounds in Amazonian Peru (Fitzpatrick 1980).
Perch Trees. The presence of prominent (i.e., above surrounding canopy) trees or snags, I particularly conifers, is a common feature of all nesting habitat. These provide a commanding view of the surroundings and serve as perches for foraging and singing. Characteristics of areas I around perch trees include 1) sufficient unobstructed air space for sallying out to hawk flying insect prey, and 2) an adequate presence of flying insects. In central Alaska, mean height of primaryperch trees (n=63) was 17.5 meters(range 6-30 meters), and perches were 1.4 times the I height of the surrounding canopy (Wright 1997). The olive-sided flycatcher's affinity for . prominent trees and snags has been suggested as a factor limiting its abUildance (Finch 1992). ·· I Foraging andFood Habits
I Foraging Methods. The olive-sided flycatcher is an aerial insectivore that generally forages from a high, prominent perch, often at the top of a snag or the dead tip or uppermost branch of the tallest trees where it flies out (sallying or hawking) to snatch a flying insect, and then returns to I · the sameor another prominent perch. Unlike other flycatcher species which may attack prey by .· hoveringand striking (e.g., gray flycatcher, least flycatcher [Empidonax minimum], Hammond's I flycatcher) or pouncing and capturing on the ground (e.g., dusky flycatcher, vermilion flycatcher [Purocephalus rubinus], dusky-capped flycatcher [Myiarchus tuberculifer]), the olive-sided flycatcher is entirely restricted to hawking (sallying) for prey (Eckhardt 1979). Based on a I literature review of foraging methods in North American breeding flycatchers of the Family Tyrannidae, the olive-sided flycatcher is the only flycatcher that depends exclusively upon one I method of foraging(Murphy 1989). It is a passive sit -and-wait predator, remaining perched until prey is sighted; but then actively purses prey including insects that areoften difficult to capture I (Eckhardt 1979). Prey. The olive-sided flycatcher is almost exclusively insectivorous, and preys mostly on flying I insects. Insects of the order Hymenoptera (bees, wasps, and flying ants), have been reported to make up a high percentage of the diet. Beal (1912) found Hymenopterans in 61 of 63 stomach samples from a number of breeding locations, and 26 of the stomach samples (41 percent) I contained no other food. Their opportunisticforaging of aggregated or social Hymenopteran prey has also been noted during migration in the Caribbean lowlands of Costa Rica where Sherry I (1984) reported one stomach with 31 flying ant queens. Hymenopterans comprised 81 percent I 11 I I
of the prey items (n= 104) based on the stomach contents of four individuals. In contrast, I Hymenopterans comprised only 10 percent of the total food volume and were present in only three of 12 stomachs examined from mixed conifer forest of the Sierra Nevada Mountains (Otvos and I Stark 1985). The principal prey items were insects from the order Coleoptera (beetles), particularly the family Scolytidae (bark beetles). Olive-sided flycatchers have also been reported to prey on flies, moths, grasshoppers, and dragonflies (Bent 1942). I
Foraging Locations. Olive-sided flycatchers forage within forest clearings, adjacent to forest edge, and over forest canopies where there are exposed perches and unobstructed air space. I Aerial hawking specialists like the olive-sided flycatcher typically forage in edge or open canopy situations because light intensity is at a maximum and prey can be spotted easier against the -solid I lighted background of the sky (Fitzpatrick 1978). Within regenerating forest in the Cascade Mountains of northern Oregon, males typically foraged from the top of prominent perch trees and snags, while females foraged closer to the ground from subdorninant and understory trees and ,, I snags (Altman in prep.). I Site Fidelity. Despite a paucity of reported banding recoveries and the absence of demographic studies, there is some data to indicate that olive-sided flycatchers may exhibit strong breeding site fidelity. Ofthe three recoveries/returns of banded olive-sided flycatchers reported to the USFWS, I Bird Banding Laboratory (among nearly 2,000 olive-sided flycatchers banded through 1995), two were recaptured in the same 10 minute block (presumably the same location) in California, five and six years afterbeing banded. The other bird was recovered in Ontario, six years after being I banded approximately 560 kilometers away from the banding location. Two birds banded during the breeding season at Big Sur in California in 1994have returned in the two subsequent breeding I seasons (Jim Booker, Big Sur Ornithology Laboratory, pers. cornm.). They were believed to have been a mated pair in 1996 because they were captured together in a mist-net with two fledglings. Incentral Alaska, an adult female banded at the nest in 1994 returned to the same territory in 1995 I (different mate in 1995), and an adult male banded in 1995 returned to the same territory in 1996 (Wright 1997). I
The extreme behavioral expression of breeding site fidelity, reuse of the same nest site from one year to the next, is rare in open-nesting passerine birds, and has not been reported for the olive I sided flycatcher. However, nest site reuse between years has been reported for other open-nesting tyrannid flycatchers, including several instances by the closely related western wood-pewee (Curson et al. 1996). I
There is also evidence to indicate sitefidelity on thewintering grounds. In Belize, the same olive I sided flycatcher was captured in January, in subsequent years (Russell 1964). In southern California, the same individual returned for six consecutive years (Lehman 1994). I 12 I I I
I Migration Phenology. The olive-sided flycatcher isgenerally considered a late migrant in spring and an early migrant in fall. Like other insectivorous flycatchers, their late arrival in spring is likely based on the timing of their foraging base, aerial insects, which are less available in the I early spring (Robins 1970, Bryant 1975). Late arrival in spring and early departure in fall may also be a function of the distance to their wintering range. The olive-sided flycatcher has the I greatest migration distance among the 32 species of North American breeding flycatchers in the Family Tyrannidae (Murphy 1989).
I Departurefrom Wintering Grounds. Olive-sided flycatchers begin leaving the wintering grounds during the last week of March, and most birds have left these areas by late April (Bent 1942). I InBrazil, most birds are gone by mid-to-late March (Stotz et al. 1992). In Peru and Venezuela, late departure dates are March 5 and April 14, respectively (Paynter 1995). Peak period of departure in Columbia begins in March (Paynter 1995). Most birds are gone from wintering
I. locations in the highlands of northern Columbia by early May, although several individuals were ,, observed in early June 1972 (Johnson 1980, Hilty and Brown 1986). In Panama, departure begins I in mid-March with a few individuals present until late May (Ridgely 1976).
Spring Migration andArrival on the Breeding Grounds. The timing of migration and arrival of I the olive-sided flycatcher within its breeding range is based on latitude and elevation. At Big Bend National Park in Texas, the olive-sided flycatcher first appears in early April with an occasional bird present until early June (Wauer 1973). The peak migration in southern California I is mid-April, and in northern Californiait is early May (Zeiner et al. 1990). In Oregon, there are a few late April records, but the peak is mid-to-late May (Gilligan et al. 1994). In Idaho, they I generally arrive in the third week in May (Burleigh 1972). Olive-sided flycatchers arrive in southern British Columbia in the latter half of May and the migration peaks in early June (Cannings et al. 1987). In central Alberta, arrival is the third week of May (Salt and Salt 1976). I In Banff and Jasper National Parks, olive-sided flycatchers arrive in late May and early June (Holroyd andVan Tighem 1983). Arrival of the olive-sided flycatcher in central Alaska is mid I to late May (Kessel and Gibson 1978).
Departure from Breeding Grounds. Fall migration in Alaska begins in late August (Kessel and I Gibson 1978). In Banff and Jasper Parks, fall migration occurs ·in August and the latest record is September 3 (Holroyd and Van Tighem 1983). In central Alberta, olive-sided flycatchers move south in mid-August andare gone by mid-September (Cannings et al. 1976). In Idaho, migrants I occur throughout August, but rarely after early Septeltlber (Burleigh 1972). Fall migration in Oregon peaks in late August-early September with a fe w late September records (Gilligan et al. I 1994). InCalif ornia, olive-sided flycatchers begin to depart from breeding areas in August, and most residents and migrants have left by early October (Zeiner et al. 1990). In general, by mid I to-late September, most olive-sided flycatchers are gone from areas within their breeding range. I 13 I I
Fall Migration and Arrivalthe on Wintering Grounds. The initial migrants at Big Bend National I Park in Texas appear in early August, and a few individuals may be present until the first of October (Wauer 1973). Mean arrival date of fall migrants over a 12-year period in San Jose, Costa Rica, wasSeptember 13 (Stiles 1994). Extreme dates of arrival and departure in Honduras I are September 2 and November 10 (Monroe 1968). The frr st migrants appear in Panama in late August and may occur until mid-November (Ridgely 1976). Initial arrival in thehighlands of I northern Columbia in 1972 and 1973 was around October 1 (Johnson 1980). Paynter (1995) indicatedthat the peak period of transients in Columbia occurred until mid-November, although Hilty (1980) reported that olive-sided flycatchers were not regularly observed in undisturbed mid I elevation rain forest of western Columbia until January. Early arrival dates in Venezuela and Peru are October 28 and 29, respectively (Paynter 1995). Initial arrival in southeastern Peru in 1976 I was November 3 (Fitzpatrick 1980). Early arrival date in Brazil is October 10 (Stotz et al. 1992). · a HABITAT ASSOCIATIONS
Winter. On the wintering grounds, the olive-sided flycatcher primarily inhabits mature evergreen I forest (Petit et al. 1995), particularly montane forest (Willis et al., 1993, Ridgely and Tudor 1994, Stotz et al. 1996). The principal location of wintering habitat is the slopes of the Andes I Mountains (Ridgely and Tudor 1994). The elevational range of wintering habitat is 700 to 3,400 meters (Stotz et al. 1996), although the species generally occursbetween 1,000-2,000 meters. Wintering habitat is similar to that on the breeding grounds - forest edges and forest openings, I especially where scattered tall trees or snags are present (American Ornithological Union 1983, Ridgely and Tudor 1994, Stotz et al. 1996). II
The olive-sided flycatcher reaches its greatest abundance in winter in the Andes Mountains of Columbia where it occurs in lightly forested areas and forest edges ranging from 400-2,600 I meters, although most records are from above 1,000 meters (Paynter 1995). In subtropical montane wet forest between 1,900 and 2,300 meters in northern Columbia, it was the most I common non-parulid (warbler) species observed (Johnson 1980). In western Columbia, it is considered an uncommon species in mid-elevation ( 1, 000 meters) forest, and is absent from lowland (100meters) and highland (1,900 meters) forest (Hilty 1980). I
Elsewhere in South America, the olive-sided flycatcher occurs in primary forest on the eastern slopeof the Ecuadoran Andes from 600 to 2,000 meters (Robinson et al. 1995). In the western I Amazon Basin of southeasternPeru, it occurs commonly in primary and secondary forest treefall gaps from500 to 2,000meters (Robinson et al. 1988). In Venezuela, published records are from I 900 to 2, 100meters (Paynter 1995), although Meyer de Schauensee and Phelps (1978) indicate it is sometimes found as low as 400 meters. It has been reported at three localities in Bolivia on I 14 I I I
I the middle and lower slopes of the Andes Mountains in November and January (Paynter 1995). In the Guianas, where it is considered rare, there are a few records, mostly in March (Paynter I 1995). In northern Venezuela, an olive-sided flycatcher was observed foraging in aty pical winter habitat of tidal scrub and mangrove flats (Fitzpatrick 1980).
I In Amazonian Brazil, the olive-sided flycatcher winters along the lower slopes of the Andes Mountains up to 2,000 meters (Stotz et al. 1992). It is considered a regular, but rare winter I visitor around Manaus, and thinly distributed elsewhere in Brazil. Recent sightings in southeasternBrazil at elevations from850 to 1,400 meters caused Willis et al. (1993) to speculate that deforestation had allowed the species to spread eastward into this well-studied region where I thespecies was previously absent. They also note that the recent spread of Afr icanized honeybees (Apis millife ra) into this area may have caused therange extension on the basis of their preference I for honey bees.
In Mexico and northern Central America, it occurs as an uncommon winter visitor in pine-oak, I evergreen, and semi-deciduous forest from 1,500 to 2,000 meters (Howell and Webb 1995). In Costa Rica, it is a rare winter resident in foothills andmountains from610 to 2,290 meters (Stiles and Skutch 1989). At La Selva in northeastern Costa Rica, it was recorded in primary forest I between 1,000 and 1,500 meters, but not in young second growth (Blake and Loiselle 1992).
I Breeding Season. The olive-sided flycatcher is primarily an inhabitant of montane and northern coniferous forest in western North America. Snyder (1950) considered it one of several species indicative of the coniferous forest biome based on its occurrence within a wide range of types of I con iferous forest. In eight forest types of the Rocky Mountains, Hejl et al. (1995) considered it common in spruce-fir and aspen; uncommon in mixed conifer, ponderosa pine (Pinusponderos a), pine-oak, and Cascadian (western hemlock/western red cedar [Thuja plicata], grand fr r, and I Pacific yew [Taxusbrevi folia]); and rare in lodgepole pine (Pinus contorta latifolia) and pinyon juniper (Pinus cembroides-Juniperus sp.) based on literature review and subjective field I experience. Based on one year of census data in the northern RockyMountains, Hutto (1995 a) reported that among undisturbed forest types, the olive-sided flycatcher occurred most frequently in spruce-fir, marsh-wetland, and mixed conifer cover types, and to a lesser degree in cedar I hemlock, Douglas-fir, ponderosa pine, lodgepole pine, and riparian shrub. Finch and Reynolds (1988) reported it was more abundant in spruce-frr habitats than in aspen or mixed aspen-conifer I in the centralRocky Mountains.
Within the coni ferous forest biome, the olive-sided flycatcher is most often associated with forest I openings, forest edges near natural (e.g. , meadows, canyons, rivers) or man-made openings, or open or semi-open stands with a low percentage of canopy cover. In Douglas-fr r forests of I northwestern California, it was the only common species detected more often on the edge of the I 15 I I
forest and a clearcut than in the interior of the forest (Rosenberg and Raphael 1986). In mixed I conifer forests of the Sierra Nevada Mountains, it was more abundant in open mixed conifer and red fir(A bies magnifica) forest than in closed canopy forest (Beedy 1981), and optimum habitat I was considered to be late-successional forests with 0-39 percent canopy cover (Verner 1980). In mixed aspen/conifer forest of west-central Colorado, olive-sided flycatcher occurred in higher densities in stands with low overstory canopy, and was absent as the overstory coverage I approached 100 percent (Scott and Crouch 1988). In grand fr r/Douglas-frr forest of west-central Idaho, olive-sided flycatcher occurrence was influenced by tall canopy height and low crown closure (Sallabanks 1995). I
The association of the olive-sided flycatcher with forest openings and forest edge has also been I documented at a landscape level. In mixed conifer forest of west-central Idaho, it was significantly more abundant in treated watersheds with clearcuts than in untreated watersheds without clearcuts (Evans and Finch 1994). In western red cedar/western hemlock forest in _ ·I northern Idaho, olive-sided flycatcher was significantly more abundant in selectively lo gged foreSt. with embedded 10-26 year-old clearcuts than in fragmented and unfragmented old-growth forest I (Hejl and Paige 1994). In the Oregon Coast Range, it was more abundant in landscapes containing highly fragmented late-seral forest with high contrast edges than in less fragmented landscapes (McGarigal and McComb 1995). However, its occurrence was not determined by the I percent of the landscape in late-seral forest (minimum 20 percent, maximum 80 percent) despite its association with late-seral forest at the patch level. I
The olive-sided flycatcher is frequently reported as a species associated with burn ed-over forest. In conifer forests of the Sierra Nevada Mountains, three studies corroborate its association with I burned forest. Raphael et al. ( 1987) noted it in moderate densities in a burn ed plot from 6-25 years post-bum, but absent from an adjacent unburned plot during the same time frame. Bock and Lynch (1970) reported it in low densities in a burn ed plot 6-8 years post-bum, but absent from I an adjacent unburned area. In red-fir forest, Granholm (1982) reported it in low densities in intense surface bum plots 1-2 years post-bum, but absent in control (non-bum) plots. I
The olive-sided flycatcher was one of 15 species more abundant in early post-fire communities than in any other major cover type in the northern Rocky Mountains (Hutto 1995a). In I Yellowstone National Park, it was recorded in low densities in 2-3 year post-bum spruce-fir plots (absent in an unburned plot), and in relatively high densities ( > 5 birds/40 ha) in 4-5 year post bum lodgepole pine bum plots (Pfister 1980). This is in contrast with the findings of Taylor and I Barmore (1980) who did not record the species in severe or moderate burn ed plots of. several different ages of lodgepole pine or spruce-frr forest in Yellowstone and Grand Teton National I Parks. At 4-years post-bum in Kootenay National Park, olive-sided flycatchers were more / common in the bum and at the edge of the bum than in adjacent mature forest (Edwards 1973). I 16 I I I
I Two studies in Alaska report contrasting results regarding olive-sided flycatcher occurrence in burnedfo rest. Inwhite sprucefo rest on the Kenai Peninsula, olive-sided flycatchers were present I in 1-year old bums and breeding in 10 and 20 year-old burns with snags, but absent from nearby 50 and 100 year-old forest (Quinlan 1979). Near the Kuskokwim River north of the Alaska Range, olive-sided flycatchers were three times as abundant in unburned white spruce forest than I in a 3 year-old bum, and absent from an 8 year-old burned forest with lots of snags (Hinkes and Engel 1981).
I Several studieshave reported on olive-sided flycatcher densities in burned Ponderosa pine forest in Arizona. In central Arizona, olive-sidedflycatcher densities were three birds per 40 ha in three I and seven years post-bum habitat, but it did not occur in one and 20 years post-bum habitat nor in an adjacent control site (Lowe et al. 1978). In northern Arizona, it was present in moderate densities in a 3-4 year post-bum site, but not in sites of 2-3 and 8-9 years post-bum nor in a I control unburned site (Overturf 1979). In central Arizona, it occurred in a partially logged area . .. - at two years post-bum, but not in an adjacent unlogged burn nor a clearcut burn (Blake 1982). I Elsewhere, in mixed conifer forest of northeastern Oregon, olive-sided flycatcher was more common in burned fo rest than unburned forest in years one and two post-fire (Sallabanks 1996). I Abundance increased in all burntypes (low, medium, and high intensity) in year two post-fire including a significant increase in the high intensity burn. Apfelbaum and Haney (1981) reported I olive-sidedflycatcher in the first year post-bum of jack pine (Pinus banksiana)lblack spruce forest of Minnesota where it had been absent in the previous year. 'Ithas also been recorded in a 1 0-year post-bum stand of lodgepole pine in southcentral Wyoming (Davis 1976). I The association of theolive-sided flycatcher with burned forest is likely due to creation of fo rest openings and increased edge at the interface of live and dead fo rest. It has also been suggested I that aerial insects increase in numbers following fires based on the positive response of several aerial insectivorous bird species to fire (e.g., western wood-pewee, townsend's solitaire I [Myadestes townsendtl ) (Granholm 1982). Hutto (1995a) noted that insectivorous diets characterized most species associated with early post-fire bird communities.
I Another frequently reported habitat association of the olive-sided flycatcher is along the wooded shores of streams, lakes, rivers, beaver ponds, bogs, and muskegs, where natural edge habitat I occurs and standing dead trees are often present (Gibson and McDonald 1975, Kessel and Gibson 1978, Godfrey 1986, Cheskey 1987). Its presence near water may also be due to higher insect abundance in theseareas. Occurrence of the olive-sided flycatcher near water is particularly true I in boreal forest in the northern portion of its breeding range. In boreal Canada, it is most common in openhabitat ofspruce and tamarack dominated muskegs, bogs, and swamps (Erskine I 1977). In Alaska, it is frequently associated with the relatively open taiga (boreal) forest of I 17 I I central Alaska (Kessel and Gibson 1978, Godfrey 1979) where it breeds in open dwarf white I spruce forests and black spruce bogs (Spindler and Kessel 1980). I The association of the olive-sided flycatcher with forest edge habitat is typically at the interface of late and early successional forest. In the Oregon Coast Range, McGarigal and McComb ( 1995) identified it as a species strongly associated with the juxtaposition of late successional (mature and I old-growth) forest and early successional open-canopy habitats. The olive-sided flycatcher has also been reported as a species closely associated with old-growth forest in the Oregon Coast .· I Range, where the tall trees and broken canopy provide a better foraging environment for aerial � sallying than closed-canopy younger forests (Carey et al. 1991). In Douglas-frr forests of northwestern California, it was significantly associated with old-growth stands ( > 250 years old) I (Raphael 1984). In mixed-conifer forests of the Sierra Nevada Mountains, Verner (1980) indicated that it occurredonly in large treehabitat . In subalpine forest of central Colorado, it has beenreported inovermature forests of Englemann spruce (Picea engelmanniz) , subalpine fir (Abies . , , ·I lasiocarpa), and lodgepole pine (Scott et al. 1982). I The presence of the olive-sided flycatcher in early successional forest appears dependent upon the availability of snags or residual live trees for foraging and singing perches. Hagar (1960) considered it a common species in the weed and brush stages of 1-7 year old cutover Douglas-fir I forest of northwesternCalif ornia, although he doesn't report on the presence of snags or residual trees. In hemlock/grand fir forests of northern Idaho, olive-sided flycatcher was most abundant in the tall shrub with few conifer life fo rm (doesn't indicate if residual snags/trees present) I (Peterson 1982). It has also been recorded during the breeding season in 20-year old stands (approximately 30 feet tall) of coastal western hemlock at the northwestern tip of Vancouver I Island (Buckner et al. 197 5) .
Several authors have indicated that the olive-sided flycatcher benefits from particular types of I logging. Hutto (1995a) reported that the olive-sided flycatcher occurred more frequently in disturbed forest (clearcuts, seed tree cuts, shelterwood cuts, group selection cuts, and post-fire) I than in undisturbed forest in the northern Rocky Mountains. It was significantly more abundant · in mixed-conifer standssubjected to selective overstory removal than in unharvested stands in the White Mountains of Arizona (Franzreb 1977, Franzreb and Ohmart 1978). Medin (1985b) and I Medin and Booth (1989) reported that it increased in abundance following commercial diameter cut logging and single-tree selection logging in a Douglas-fir forest in west-central Idaho. In a western larch/Douglas-frr forest of northwestern Montana, it was more abundant in logged I (clearcut and partial-cut) than in unlogged forest (Tobalske et al. 1991). In subalpine forest of central Colorado, the olive-sided flycatcher population increased significantly in a 40-ha drainage I where 36 percent of the drainage was harvested with 12, 1.2-ha circular clearcuts (Scott et al. 1982). I 18 I I I
I Some types of forest management have not affected olive-sided flycatcher populations. Forest understory clearing and burning of live and dead trees and brush did not result in an increase in I olive-sided flycatcher populations in sequoia forest of the Sierra Nevada Mountains in California (Kilgore 1971). Small (2-8 ha), salvage clearcuts in spruce budworm infested conifer forest of eastern Maine did not affect olive-sided flycatcher abundance during the first year after treatment I (Derleth et al. 1989). I The olive-sided flycatcher occurs with less regularity and abundance in deciduous or mixed- . deciduous/coniferous forest. It hasbeen reported in aspen in Colorado and Wyoming (Finch and Reynolds 1988, Turchi et al. 1995), clearcuts surrounded by mature aspen in southwestern I Colorado (Scott and Crouch 1987), mixed aspen/conifer in Colorado (Scott and. Crouch 1988), 20-30 year-old aspen/spruce mixed woodfor est in Alberta(Schick and Nietfeld 1995), and spruce poplar boreal forest in the Yukon (Theberge 1976). Other deciduous or mixed
I _ deciduous/coniferous habitat where it has been reported include mixed Douglas-ftr/madrone ,, (Arbutus menziesiz)loaks in western Oregon (Cross and Simmons 1983), black oak woodlands in I the western Sierra Nevada Mountains of California (Verner and Boss 1980), red alder (Alnus rubra) in western Washington (Stiles 1980), eucalyptus groves in California (Shuford 1993, I Peterson 1990), and cottonwood (Populus sp.) in northwestern Nevada (Weitzel 1988). The olive-sided flycatcher may occur at any elevation from sea level to timberline, but usually I occurs in mid-to-high elevation (920-2, 130 meters) forest throughout the .mountains of western North America. It has been reported up ro·2,600 meters in mixed ponderosa pine and white frr forest of southern Nevada (Johnson 1965b), at 2,750 meters in mixed aspen/conifer forest in west I central Colorado (Scott and Crouch 1988), at 3,050 meters in subalpine forest of central Colorado (Scott et al. 1982), and 3,350 meters in New Mexico (Ligon 1961) and in the San Pedro Martir Mountains of southern California (Bendire 1895). In northern Baja California it breeds in pine I forest from 2,000-2,800meters (Howell andWebb 1995, Stotz et al. 1996). Records of breeding birds at low elevations include 60meters near Santa Clara, California (Smith 1927), and near sea I level at Berkeley, California (Dixon 1920).
Migration. Minimal information is available on olive-sided flycatcher habitat use during I migration. Where it has beennoted during migration, a greater diversity of habitats are used than during the breeding season, with particularly more use of riparian and non-coniferous habitats. I It has been reported in spring migration in Arizona in a heterogeneous deciduous riparian forest of sycamore, ash (Fraxinus sp.), and hackberry (Celtis sp.)(Stevens et al. 1977). In Nevada, it is also a transient in riparian areas, particularly during spring migration (Alcorn 1988). Migrant I birds in Mexico and northern Central America use pine-oak, evergreen, and semi-deciduous forests and edge (Howell and Webb 1995). In Honduras, where it is considered an uncommon I transient, it occurs primarily inthe highlands from 600 to 1,600 meters, although it occasionally I 19 I I migrates through the lowlands on both coasts, especially in fall (Momoe 1968 ) . In Guatemala, I it occurs as a uncommon transient in pine and oak woodland and woodland edge from 300 to 2,600 meters (Land 1970). Itis an uncommon to fairly common migrant in Costa Rica from the lowlands to 2,500 meters and rarely to 3,050 meters (Stiles and Skutch 1989). A fall migration I stopover site in San Jose, Costa Rica, where 17 olive-sided flycatchers were banded over a 12- year period, was characterized as second growth scrubby woodland on an abandoned coffee plantation (Stiles 1994). I
Habitat use and/or migration route may vary between spring and fall. During three years of mist- · I netting in several woodland habitat patches in northern Minnesota, olive-sided flycatchers were nearly absent during spring migration (2 birds captured), but fairly regular in fall (52 birds captured) (Winker et al. 1992). Data from over 25 years of censusing and bandiiig on Southeast I Farallon Island indicated that the olive-sided flycatcher was substantially more common in spring (n = 103) than in fall (n =69) (Pyle et al. 1994). It is a considerably less common migrant in ·· ' I spring thanfaU in Honduras (Momoe 1968), and often an abundant migrant along the Caribbean ·. coast of Costa Rica in fall (Stiles and Skutch 1989). Young birds may account for the higher numbers during fall migration, however the example from Southeast Farallon Island suggests I seasonal differentiation in migration routes. A noteworthy inference regarding migration route is a tape-recording of an olive-sided flycatcher in Trinidad that was identified by the Cornell I Laboratory of Ornithology as typical of an olive-sided flycatcher from western North America (ffrench 1991). I POPULATIONS I The BBS (Robbins et al. 1986) is the primary source of population status and trend information for North American landbirds, and it provides the best available data for estimating abundance and I trends of breeding populations of the olive-sided flycatcher . This volunteer-based population monitoring program is administered cooperatively by the U.S. Geological Survey, Biological Resources Division and the Canadian Wildlife Service. Despite well-documented limitations and I biases in the survey methodology and controversies surrounding the analyses of BBS data (Droege 1990, Sauer et al . 1994, Peterjohn et al . 1995, Kendall et al . 1996, Thomas and Martin 1996), I it is the accepted measure of the status of North American breeding bird populations.
Monitoring. Theolive-sided flycatcher can be effectively monitored during the breeding season I by any standardized census relying on vocalizations to determine presence or abundance. It is readily recognized by its song and is highly detectable based on 1) a high frequency rate of singing, and 2) a propensity to sing from the top of the highest trees or snags where sound I attenuation by absorption from vegetation is not reduced and vocalizations carry relatively large I 20 I I I
I distances. McGarigal and McComb (1995) calculated an effective detection distance of 150-175 meters for olive-sided flycatchers in mixed-conifer forest of the Oregon Coast Range. Mean I detection distance in black spruce forest of central Alaska was 654 meters (range 514-828 meters) . Incertain topographic situations, a singing olive-sided flycatcher can be readily detected up to 1/2 I mile away (Altman in prep.). Censusing with unlimited distance detections (e.g., BBS routes) may be most effective for monitoring olive-sided flycatchers. Census techniques requiring distance estimation to detected I birds (e.g., variable width point count or transects) may be less effective than unlimited distance censuses because of 1) inherent difficulties in estimating distances to singing birds beyond 50-75 I meters, and 2) specific difficulties in estimating distance to a singing olive-sided flycatcher because of the expansive carrying capacity of its song (see explanation above) . Fixed radius point count or transect censusing is also less effective than unlimited distance censusing because olive
I sided flycatchers are most frequently detected beyond the distance of the fixed radius (i.e., usually . . . 50 meters, but also 75 or 100 meters), and thus often not included in most of the analyses I conducted for those data sets .
The BBS is effective for censusing olive-sided flycatchers because it does not require distance I estimation and it has no fixed distance radius . Indeed, the olive-sided flycatcher is highly suited to monitoring by the BBS for several reasons. Biases associated with the BBS such as I detectability, observer differences, and roadside sampling (Bystrak 1981, Droege 1990), are reduced for the olive-sided flycatcher. It is highly detectable based on the frequency and strength · of its song; the song is easily learned, readily recognized, and generally not confused with any I other song; and it is frequently associated with roadside edge habitat and can be detected at relatively long distances if not associated with the roadside. Additionally , because it has a large territory size for a passerineand is highly detectable at relatively long distances, abundance indices I from BBS data are likely to chapproa actual abundance. With BBS stops at 112 mile intervals and the potential to detect olive-sided flycatchers up to 112 mile, it is likely that only one or two pairs I of olive-sided flycatchers actually occur between BBS stops, and these may be detectable from either stop if topography does not preclude this.
I Monitoring demographic parameters (reproduction, survivorship, recruitment into the population) of olive-sided flycatcher breeding populations is problematic. Continental programs such as I Monitoring Avian Productivity and Survivorship (MAPS), Breeding Biology Research and .. Monitoring Database (BBIRD), and Bird Population Studies (BPS) of Cornell Laboratory of Ornithology provide data on landbird demographic parameters, but are generally ineffective in I monitoring demographics of olive-sided flycatcher populations. In western North America, the MAPS program has records of 93 captures (76 new captures and 13 recaptures) of olive-sided flycatcher from 11 stations through 1995 (Ken Burton, Institute for Bird Populations, pers. I comm.). The small sample size of banded birds isthe re sult of difficulties in capturing olive-sided I 21 I I flycatchers due to their propensity to fly near canopy level and in open areas not usually sampled I by mist-nets. The BPS data base has nest record cards on 56 olive-sided flycatcher nests since 1904 (Jim Lowe, Cornell Laboratory of Ornithology, pers. comm.), and BBIRD has data for only one olive-sided flycatcher nest (Eric Reimer, University of Montana, pers . comm.). The limited I data on nests is likely a result of the difficulty in finding and monitoring nests due to their location and height above ground, and their low nesting density which requires large search areas. I However, the location of 50 olive-sided flycatcher nests during one year (two people full-time) inthe Cascade Mountains of northern Oregon represents the largest database on nests and nesting success in one area , and indicates the potential for monitoring olive-sided flycatcher productivity I (Altman in prep.). I Monitoring olive-sided flycatchers during migration is also problematic . Dunn and Russell (1995) listed olive-sided flycatcher as one of 40 species that would most effectively be monitored in Canada by migration monitoring, because more than half the breeding range in Canada is in ' I remote areas north of road accessibility, and thus not monitored by the BBS . However, the two principal means of migration monitoring, censusing and mist-netting (Dunn and Hussell 1995), are relatively ineffective for the olive-sided flycatcher. Olive-sided flycatcher vocalizations are I substantially reduced afterthe breeding season, so censusing during migration relies primarily on visual detections, which are considerably less frequent. As stated above, olive-sided flycatchers I are captured in mist-nets relatively infrequently, and migration monitoring may be most effective with the placement of canopy nets in areas known to be regularly used by olive-sided flycatchers in migration. I
Trends . Most historical information on the status and trends of nongame birds is anecdotal and I localized in the eastern United States (Petetjohn et al. 1995). The earliest comments regarding olive-sided flycatcher populations were declines in the Cambridge, Massachusetts area between 1870 and the tum of the century (Brewester 1906). Elsewhere in eastern North America, some I authors suggest that olive-sided flycatcher populations have increased since historical times due to logging that has opened up the close-canopied forests (Fichtel 1985, Erskine 1992) . I
BBS data indicates widespread declines in olive-sided flycatcher populations (Table 1). The declines are relatively consistent in magnitude across its breeding- range, with the overall rate of I decline of 3.9 percent per year based on BBS data from 1966 through 1996. The declines are similar within the political boundaries of the United States and Canada (4. 1 and 3.7 percent per year, respectively) , and within eastern and western North America (3 .5 and 4.1 percent per year, I respectively) . I I
22 I I I
I Table 1. Breeding Bird Survey regional and continental population trend estimates for the olive
sided flycatcher' 1966-1996. a I I
I Eastern 278 0.90 -0.9 163 -4.5 North I America
Western -4 . 1 *** 423 2.12 -2 .8 ** 182 -2.9 *** 384 North I America
United -4 . 1 *** 444 1.51 -2 . 3 ** 209 -3.9 *** 379 I States I Canada -3.7 *** 239 1.27 -2.0 138 -2.9 *** 192 North -3.9 *** 683 1.39 -2.1 * 347 -3.5 *** 571 I America
a Sauer et al. (1997); trends estimated by the route-regression method (Geissler· and Sauer 1990) I b average percent annual change c statistical significance of the trend *** P
I 23 I I
BBS data also indicate widespread declines at the state/province and physiographic region levels I (Tables 2 and 3). Guidelines for interpretation of BBS data caution that physiographic region or state/province analyses based on fewer than 14 routes may be suspect (Bruce Peterjohn, Breeding I Bird Survey, pers. comm.). On the basis of these guidelines, there are no BBS physiographic provinces with a significant positive trend estimate, and significant declines are indicated for 10 physiographic provinces (Table 2). This includes eight physiographic provinces with a highly I significant (P < 0.01) decline, seven of which are in western North America; Sierra Nevada Mountains (3.8 percent per year), Cascade Mountains (2.9 percent per year) , Southern Pacific I Rainforests (5 .1 percent per year) , California Foothills (5 .2 percent per year), Fraser Plateau (9 .7 percent per year), Northern Spruce-Hardwoods (4.0 percent per year), and Northern Pacific Rainforests (5.2 percent per year). I Of the 15 states andprovinces within western North America, eight have significant negative long ·I term (1966-1996) trend estimates (Table 3). Three of the eight are highly significant (P < 0.01); _ British Columbia (5.3 percent per year), California (4.0 percent per year), and Oregon (5 .1 percent per year) . The only state/province with a significant positive trend estimate is Alberta I (6 .1 percent per year). It is unclear why the annual trend estimate for Alberta is positive, particularly when it is surrounded by provinces/states with significantly negative trends. However, the large value of the trend estimate and a relatively high variance indicates that the I trend estimate is relatively imprecise, and probably is a poor representation of the actual population trends (Bruce Peterjohn, Breeding Bird Survey, pers. comm.). I
Further examination of the BBS data indicates that the greatest declines are occurring primarily west of the Rocky Mountains (Figure 3) in regions that also support the highest relative abundance I of the species (Table 2, Figure 4). For example, the highest abundances occur in the Sierra Nevada Mountains (12.4 birds per route[bpr]), the Cascade Mountains (5.3 bpr), the Southern Pacific Rainforests (3 .9 bpr) , and the Fraser Plateau (3.6 bpr), all of which have highly significant I (P < 0.01) population declines. Thus, it is from the core of the species population that declines are the greatest. Unlike some species of concern where declines at the edges of the species range I have reduced overall distribution, declining populations associated with olive-sided flycatchers are apparently greatest where the habitat is most suitable and within the core of the species' population. I
Several other analyses of BBS data corroborate declining population trends for the olive-sided I flycatcher. Hejl (1994) reported that the significantly declining trend of 3.5 percent for olive sided flycatcher during the period 1968-1991 was the most negative trend of all coniferous forest bird species in the western United States and Canada. Saab and Rich (in press) reported I significant (P <0.05) declining trends of 2.9 percent (26-year) and 4.2 percent (10-year) in the Interior Columbia River Basin which includes parts of Oregon, Washington, Idaho, Montana, I 24 I I
I I I Southern Pacific -5.1 *** 70 3.9 Rainforests I Northern Pacific -5.2 *** 21 2.5 Rainforests I Southern Alaska Coast 5.8 7 1.7
a Sauer et al. (1997); trends estimated by the route-regression method (Geissler and Sauer 1990) b average percent annual change c statistical significance of the trend *** P<0.01 ** P<0.05 and > 0.01 I
* P
I Table 3. Breeding Bird Survey state/province population trend estimates for the olive-sided b flycatcher' 1966-1996. a I I
I Alaska -6.21 * 27 1.3 I Alberta 6.1 ** 24 0.4 Arizona 3.3 7 0.7
British Columbia -5.3 *** 68 2.3 I ,, California -4.0 *** 92 4.8
I Colorado 2.9 27 1.7 I Idaho -6.8 ** 21 1.2 Maine -3.1 37 0.7 I Manitoba -20.0 ** 4 0.3 Michigan 0.2 11 0.2
I Minnesota -4.7 21 0.5 I Montana -5 .8 ** 18 0.7 New Brunswick -7.6 ** 28 1.9 I Newfoundland -4.1 7 0.5 New Hampshire -6.6 *** 13 0.2
I New Mexico -5.6 7 0.4 I New York -8.5 *** 20 0.6 Nova Scotia -4.5 21 1.7 I Ontario -4.5 *** 45 0.9 *** I Oregon -5.1 69 3.8 27 I I I I I Prince Edward Island -10.1 4 0.8
Quebe� -0.3 42 1.5 I Saskatchewan -4.3 3 0. 1 I Utah -2.1 10 0.9 Vermont -7.0 *** 13 0.3 I Washington -2.8 * 48 2.3
Wisconsin 2.3 15 0.1 · I Wyoming -1.4 10 0.2 I Yukon -2.9 18 3.2 I a Sauer et al. (1997); trends estimated by the route-regression method (Geissler and Sauer 1990); b trend estimates for Alaska, Arizona, Michigan, Newfoundland, New Hamphshire, New Mexico, Prince Edward Island, Saskatchewan, Utah, Vermont, and Wyoming are through 1995 only I c average percent annual change d statistical significance ofthe trend *** P<0.01 I ** P<0.05 and > 0.01 * P
Olive-sided flycatcher Contopus borealis
11'1 "j...,..,... v /o l�.j r..l�e p€r 1 e!J'
· ·< -1 . 5
- • 1 . 5 - -0.26
1::::::::::1 - 025 - 0.25 .. 015 - 1.5
� ') �· ... ·t�\.-
Figure 3 . Olive-sided flycatcher annual population trend estimates based on Breeding Bird Survey data. Olive-sided flycatcher Contopus borealis
Average Co1Jnt . < 1 ·1-3 3-10 • n- .3/J . jJ -XJO D > 100
Figure 4. Olive-sided flycatcher relative abundance indices on Breeding Bird Survey routes.
------I
I Wyoming, Nevada, Utah, and California. DeSante and George (1994) analyzed BBS data from the western United States using Carter and Barker's (1993) population trend ranks, and also reported significantly declining trends for theentire period of BBS data ( 1966-1991) and the most I recent 13 years ( 1979-1991). However, an analysis of BBS data in Canada for the period 1966 to 1989 indicated no significant population trend in each of the three regions (southern British I Columbia, central Ontario and Quebec, and the Maritimes) with sufficient data for analyses (Dunn 1991).
I In western North America, some site-specific studies outside of the BBS corroborate declines in olive-sided flycatcher populations. Significant declines have been reported in both spring and fall I migrants at Southeast Farallon Island, California based on censusing over a 25-yem.- period, 1968- 1992 (Pyle et al. 1994). In the Puget Sound area near Seattle, olive-sided flycatchers were considered common at the tum of the century (Bent 1942), yet they are infrequently encountered I at this location today. Marshall ( 1988) noted the disappearance of the species between the 1930s and 1980s in unaltered sequoia forest of the southern Sierra Nevada Mountains. -
I Two site-specific studies have suggested a long-term increase in olive-sided flycatcher populations. Johnson and Cicero ( 1985) reported a probable increase in the olive-sided flycatcher population I between 1936 and 1983-84 in mixed-conifer forests of the San Benito Mountains of southern California. They acknowledged that some habitat change resulting from fire and logging may have resulted in the population increase, but hypothesized that documented climatic change was I likely responsible for the increase in olive-sided flycatcher and other boreal species populations.
Inthe Sheep and Spring Ranges of southern Nevada, Johnson (1965b) observed several olive-sided ·· I flycatchers in 1963 in an area where the species was absent in 1932. He acknowledged that its absence in 1932 may have been due to an irregular residency because of the marginal quality of the habitat due to its small size and isolation from similar habitat. Raphael et al. (1988) I hypothesized a two percent increase in current olive-sided flycatcher populations over historic populations in Douglas-fir forests based on current densities and estimates of current and historic I forest area in each seral stage. _ Abundance/Density. Data from the BBS through 1996 indicates that the center of abundance I for the olive-sided flycatcher (on the basis of bpr) is western North America. Specifically, this includes the states of California (4.8 bpr) , Oregon (3.8 bpr), Washington (2 .3 bpr), and the Canadian provinces of British Columbia (2.3 bpr) and Yukon Territory (3.2 bpr). In western I North America, more than 1.0 bpr also occurs in Alaska (1.3 bpr), Colorado (1.7 bpr) and Idaho (1.2 bpr). Comparatively, the onlyplaces in eastern North America with greater than 1.0 bpr are I the Canadian provinces of New Brunswick (1.9 bpr) , Nova Scotia (1.7 bpr), and Quebec (1.5 bpr). I I 31 I I
Examination of BBS data by physiographic region furtherdefines the center of abundance of olive I sided flycatcher populations within the western United States . The two physiographic regions with the highest relative abundance are the Sierra Nevada Mountains (12.4 bpr) and the Cascade Mountains (5 .3 bpr) . These regions generally represent a contiguous linear band of habitat I stretching from southern California into southern British Columbia. Additionally, relatively high abundances occur in the Southern Pacific Rainforests (4.0 bpr) and the Fraser Plateau (3 .6 bpr) I which are adjacent to or a continuation of the Sierra Nevada and Cascade Mountains. Two other physiographic regions in western North America with relatively high abundances are the Pitt Klamath Plateau (3.5 bpr) and the Northern Rocky Mountains (3.2 bpr) . I
The relative importance of several physiographic regions to the olive-sided flyc�tcher has been I examined at a coarse level with non-BBS census data. Weins (1975) summarized breeding bird census data from a range of coniferous forest types in North America, and reported that olive sidedflycatcher occurred in 56 percent of the censuses in the Sierra Nevada Mountains, 28 percent I of the censuses in Northwest Coastal forests, and 23 percent of the censuses in the Rocky · · Mountains. These frequency of occurrence data generally concur with BBS data on abundance by physiographic region, and with the following two studies. Hejl et al. (1988) censused I throughout true ftr (white frr and red frr ) forests of the Sierra Nevada Mountains and recorded olive-sided flycatcher in 61 percent of the sites. Raphael (1987) examined data from 19 studies I in subalpine forest (Englemann spruce, subalpine fir, and lodgepole pine) in the central Rocky Mountains and reported that olive-sided flycatcher occurred in 30 percent of the 54 sites censused. I
THREATS AND LIMITING FACTORS I
Several factors have been suggested as contributing to population declines experienced by the olive-sided flycatcher, although there have been no studies to examine these factors. Data are I unavailable to correlate breeding and wintering locations of a specific population, which precludes our ability to assess the relative importance of changes in wintering and breeding habitats on local orregional populations. For example, it may be that some olive-sided flycatcher populations are I relatively unaffected by forest management practices on the breeding grounds, but these populations may winter in areas where tropical deforestation has been particularly extensive. I Thus, our knowledge is deficient, and the following discussion is speculative and based on available lines of evidence that suggest potential threats and limiting factors. I Winter. Onthe basis of the relative consistency of population declines throughout the breeding range of the olive-sided flycatcher, initial speculation on reasons for the declines has focused on I habitat alteration/loss on the wintering grounds. This was also suggested by the observations of Marshall (1988) who noted the disappearance of the species between the 1930s and 1980s in I 32 I I I
I sequoia forest of the southern Sierra Nevada Mountains despite no manipulation or alteration of the habitat. Speculation that problems may be occurring on the wintering grounds is further supported by Petit et al . (1995) who identified the olive-sided flycatcher as one of 45 Nearctic I migrant landbirds most likely to be adversely affected by destruction of tropical forests, including one of the 12 most highly vulnerable species (Petit et al . 1993). I Most winter populations of the olive-sided flycatcher are restricted to primary forest in the low-to mid elevation forests of the Andes Mountains; forests which are under severe threat from logging
I and conversion to coffee, cacao, and coca plantations (Robinson et al . 1995). These areas are ·. recognized by some as the greatest conservation concern for Nearctic migrants in South America I (Robinson et al. 1988, Robbins et al. 1992). Indeed, consensus among researc.hers is that the montane foothills of the Andes Mountains have been deforested more extensively than any other forest type in the neotropics except for the nearly extirpated Atlantic coastal forests of Brazil I (Robbins et al. 1992). Inter-Andean valleys are almost completely deforested, and 85 percent of the montane forests have been altered (Orejuela 1985).
I The significance of habitat loss on the wintering grounds due to tropical deforestation has been widely discussed by ornithologists studying Nearctic migrant landbirds. Attempts to quantify that I loss and its affect on populations have also been conducted (Myers 1985, Diamond 1991). On the basis of projected deforestation rates, Diamond ( 1991) calculated that the olive-sided flycatcher would lose 39 percent of its wintering habitat between 1980 and 2000. This is in addition to I habitat loss occurring prior to 1980. He cautions that loss of winter habitat does not necessarily translate into lower breeding populations, but notes that it is reasonable to assume that a· species I losing over a third of its winter habitat in combination with earlier ·losses of habitat is likely to experience population declines.
I The suggested relationship between declining olive-sided flycatcher populations and changes in wintering habitat is supported by similarities with the cerulean warbler (Dendroica cerulea). Like the olive-sided flycatcher, cerulean warbler wintering habitat occurs within the ecological zone I of primary forest in the foothills of the Andes Mountains (Robbins et al . 1992). The cerulean warbler has also experienced significant range-wide declines at a similar rate to the olive-sided I flycatcher, 3.4 percent per year (Robbins et al . 1992). Thus, impacts on forest habitat in the Andes Mountains may be adversely affecting both species. Additionally, factors contributing to population declines in the cerulean warbler are also occurring on the breeding grounds where its I floodplain deciduous forest habitat has been lost and degraded extensively over the last 50 years (Robbins et al. 1992). Similarities between these species' wintering grounds habitat I loss/degradation and overall population declines suggest that contributing factors to declining olive-sided flycatcher populations may also be occurring on the breeding grounds, just like that I observed for the cerulean warbler. I 33 I I
Breeding Season. Threats to olive-sided flycatchers on the breeding grounds include several I factors such as habitat loss through conversion to non-forest, alteration of habitat from forest management practices (e.g., clearcutting, fire suppression), availability and acquisition of food resources, and impacts on reproductive success fr om nest predation or parasitism. I
Habitat Loss. Inwestern North America, loss of forest habitat fromconversion to non-forest has I' occurred primarily in lowland forests through encroaching urbanization and residential development. This habitat loss was most extensive during settlement of the west, but still continues to a lesser degree. I It is noteworthy that in eastern North America most forests were cleared in the. 17th and 18th I centuries by European settlers, and now human alteration of the remaining forests is minimal, but olive-sided flycatcher populations continue to decline in these areas. It has been suggested that factors adversely affecting olive-sided flycatcher populations in eastern North America include the closing of forest openings from fue suppression, urban sprawl into forest edges, loss of wetlands · · and their associated forest edge habitat, and reforestation of abandoned farms (Peterson and Fichtel 1992). I
Forest Management. During the time frame of detected population declines (the past 30 years), I forest management of coniferous forests in western North America has likely been both beneficial and detrimental to the olive-sided flycatcher. In general, there has been an increase in forest openings and edge habitat which has seemingly increased habitat for the olive-sided flycatcher. I Yet, Hutto (1995b) expressed concern that this dichotomy of increased habitat availability and declining populations may indicate that the occurrence of the olive-sided flycatcher in harvested I foresthabitat represents an "ecological trap"; where the habitat appears suitable, but reproductive success and/or survivorship is poor due to factors such as limited food resources or high rates of predation orparasitis m. Hutto suggests there is an urgent need to monitor productivity of olive I sided flycatcher populations in these human-induced habitats and determine if census data is a misleading indicator of population health. A pilot project initiated in the Cascade Mountains of northern Oregon in 1997 is addressing these concerns (Altman in prep.). I
Prior to European settlement of western North America, fr res were the most prevalent major I disturbance on the forested landscape (Gruell 1983, Agee 1991). Most of the landscape of coniferous forests in the western North America evolved under a regime of high intensity, large scale "crown" fires. These occurred at various intervals; 50-100 years in the drier forests of the I Rocky Mountains (Fischer and Bradley 1987), 100 years in the boreal forests of northeastern Minnesota (Heinselman 1973), 130-150 years in the mesic-to-dry Douglas-fir forests of the I Cascade Mountains, and an average of every 230 years in the moist forests of the Pacific Northwest coast (Agee 1991). Additionally, low intensity "surface" fires occurred more I 34 I I I
I frequently, especially in drier forests. The fr re-maintained, pre-settlement forested landscape of western North America was likely favorable olive-sided flycatcher habitat - extremely patchy with I uneven-aged forest mosaics and open park-like stands with a high degree of edge habitat.
In the last 50- 100 years, fire has been replaced by timber harvesting and fr re suppression. Fire I suppression management on state and federal lands was imposed in the early 1900s. Fire suppression has altered the natural fr re regime; consequently , the structure of many forests has I changed from open to closed canopies (Hejl et al. 1995). The ability of forest management to mimic natural disturbance regimes and the patchy landscape I caused by stand replacement fires has been questioned (Bunnell 1995, Hutto 19951:1). A principal difference between burned and logged sites is the presence of snags and residual live trees, important features to olive-sided flycatchers for food acquisition and singing perches. Clearcutting, a prevalent forest management activity in the past 50 years, creates forest openings I ,, and edge habitat, but removes most, if not all, residual live trees and snags . · Additionally, clearcuts disturb areas in unnatural patterns compared to those created by fr re (Ohara et al . 1994) . I Small and large patches of live trees frequently occur within burned forest, providing increased edge habitat and a diversity of micro-climates. Recent emphasis on salvage logging which I removes snags may also diminish olive-sided flycatcher habitat suitability.
Hutto ( 1995a) notes that conditions created by stand-replacement fr res are biologically unique, I particularly the ecosystem structure and functions provided by standing, dead trees. The differences may be important for the olive-sided flycatcher, and forest openings and edge habitat I created by harvesting may provide only the appearance of post-frre habitat, but be lacking in attributes or resources required by olive-sided flycatchers for successful reproduction and survivorship (i.e. , an ecological trap) (Hutto 1995b) . Thus, suppression of fr re, particularly stand I replacement fires over the past 50-100years, may have reduced suitable habitat for the olive-sided flycatcher, and be a principal contributing factor in population declines. I Bunnell ( 1995) also suggests that because fire historically played a significant role in shaping forest composition and structure in north temperate North America, it is likely that a significant I proportion of the fauna may be adapted to natural forest-fire regime� . If the olive-sided flycatcher evolved to depend upon early post-fire habitat, then it has likely been negatively affected by fr re I control policies. In much of western North America, forest management for timber production has converted large I areas of late-successional forest and other natural coniferous forest habitat to young conifer plantations. This reduction in late-successional forests and stand conversion to younger I successional stages has been suggested as a threat to olive-sided flycatcher populations (Finch I 35 I I
1992). Although not a late-successional obligate species, olive-sided flycatchers are frequently I assocaited with late-successional forest and tall, old trees or snags characteristic of old-growth. The dramatic loss of old-growth forest in western North America potentially represents a loss of I suitable habitat for the olive-sided flycatcher.
The effect of habitat loss/alteration on declining olive-sided flycatcher populations may be I exacerbated by three factors related to the species' biology 1) it is highly territorial on both the breeding and wintering grounds, 2) it has a high degree of foraging specialization, and 3) there are indications that it exhibits strong site fidelity on both the breeding and wintering grounds. · I Where winter habitat is saturated as deforestation reduces habitat area, some individuals may be forced to seek territories in marginal habitat, decreasing their likelihood of survival. Habitat I alteration of tropical forests has been shown to result in microclimate changes that may adversely affect insectpopulations (Canaday 1997); thus, any degree of foraging specialization, such as the olive-sided flycatcher for Hymenopterans, can result in heightened vulnerability for that species. I Additionally, species with high site fidelity may be less adaptable to habitat degradation and loss (Warkentin and Hernandez 1996), and more vulnerable to population loss. I
Foraging and Food Resources . Their high degree of specialization for flying insects, and potentially for prey in a particular phylogenetic group (i.e., Hymenopterans), suggests the I potential for availability of prey as a limiting factor. Hejl et al. (1988) suggested that local population declines may occurfor many insectivorous birds in years of heavy snowfall in true-fir forests of the Sierra Nevada Mountains. Insectivores in general, particularly aerial insectivores, I commonly experience food shortages and nestling starvation (Lack and Lack 1951, Davies 1977, Murphy 1983b, 1989) This type of effect on productivity may account for short-term, annual I population declines, but is not a likely cause of range-wide 30-year declines.
Predotion . There are no published reports of predation on adult olive-sided flycatchers, although I their size and exposure at forest edge habitats may make them prey targets for forest accipters. Tyrannids are well known for aggressive defense of thenest and territory (Bent 1942), which may I minimize nest predation. Murphy (1983b) and Martin (1987) hypothesized that flycatchers exhibiting a strong nest defense to reduce predation may be an evolutionary response to the constant threat of unpredictability of their food resource, which ·when it occurs would result in I reduced fe cundity and survival . In spruce forest of central Alaska, nest predation was 50 percent (n=14), including predation during laying, incubation, at hatching, and during the nestling period (Wright 1997). In the Cascade Mountains of northern Oregon, nest failure (assumes predation) I (n=38 ) was also 50 percent (Altman in prep.). I Nest Parasitism. The olive-sided flycatcher is a rare host species for the brown-headed cowbird (Molothrus ater) (Ehrlich et al. 1988). This may be due to an aggressive defense of the nest site, I 36 I I I
and the likelihood that opportunities for parasitism by cowbirds are relatively small because olive I sided flycatchers often nest in mountainous, remote areas where cowbird presence is minimal. There are no records of nest parasitism in the data on 56 nests reported to the Nest Record I Program of the Cornell Laboratory of Ornithology (Jim Lowe, Cornell Laboratory of Ornithology, pers. comm.). Four records of cowbird parasitism on olive-sided flycatcher nests have been reported (Friedmann 1934, Friedmann 1963, Friedmann et al. 1977) . These include records from I Alberta, British Columbia, and California. There is no direct evidence to ascertain if olive-sided flycatchers will remove cowbird eggs from parasitized nests. I Nest Competition. Weitzel (1988) reported that the aggressive behavior of invading European starlings (Stumus vulgaris) caused olive-sided flycatchers to abandon nesting attempts where they I previously nested (over a five-year period) in Fremont cottonwood trees in northwestern Nevada. I Migration. The olive-side flycatcher may also be experiencing problems during migration that may contribute to population declines. Because of the large distance between breeding and- . ·· wintering grounds, the olive-sided flycatcher has a prolonged migration (approximately 1-2 I months) which increases vulnerability duringthis part ofthe life cycle. Probable factors affecting olive-sided flycatchers in migration are similar to those on breeding and wintering grounds such as habitat loss/alteration, unpredictable fo odresou rces, environmental contaminants, and mortality I from predation.
I Other Natural or Man-made Factors
Pesticides . Pesticides have been suggested, nut not documented, as a potential threat on the I breeding grounds (Finch 1992). Pesticides may also be a threat on the wintering grounds or during migration outside of North America where pesticide use is less restricted. Pesticide effects I are primarily indirect, such as elimination of important prey which may decrease reproductive success, or in severe cases reduce survivorship of adults.
I Forest Health. In the southern Appalachian Mountains of eastern North America, the loss of coniferous forest due to insect damage and acid rain has been suggested as a threat to olive-sided flycatchers (LeGrand and Hall 1989). Inwestern North America, a,cidrain is not a threat to forest I health, but the death of large areas of forest due to insect damage would likely limit nesting opportunities (reduce live tree availability) and may affect prey availability. I Inadequacy of Existing Regulatory Mechanisms. In western North America, the olive-sided flycatcher is not on any State or Federal list that provides regulatory protection. It is listed as a I "species of concern" by the states of Alaska and California (Table 4) and a "species of management concern" by the USFWS (USFWS 1995) which is an administrative status that I suggests but does not require management consideration or protection. State Natural Heritage 37 I I I
Program rankings vary, but generally rate the species as secure with some long-term concern for I populations (Table 4) . Thus, in western North America the olive-sided flycatcher receives no specific protection by land management or regulatory agencies. I Indirect protection of the species and its habitat occurs through implementation of various legislation . The Migratory Bird Treaty Act of 1918 provides protection from direct take of the I olive-sided flycatcher, but not protection of the species habitat. Indirect protection of habitat may occur through management of legally protected species (e.g., protection of old-growth forest for spotted owls and marbled murrelets) . Additionally, Federal regulations such as the Forest I Management Act of 1976, The National Environmental Policy Act, and Section 404 of the Clean Water Act may provide some indirect protection of habitat. I
CONSERVATION AND MANAGEMENT ,. I
Establishing guidelines for the management and conservation of the olive-sided flycatcher is hampered by a lack of natural history information on the species, and an absence of knowledge ' I of specific factors adversely affecting the species. Until these types of data are available, conservation strategies are speculative, and dependent on management that provides habitat I suitable to olive-sided flycatcher occurrence and abundance, despite an absence of knowledge of olive-sided flycatcher population viability in these habitats. I If the olive-sided flycatcher is adapted to the natural disturbance of stand-replacement fires, then silvicultural practices that approximate natural disturbance regimes caused by fire will likely provide the best habitat for the olive-sided flycatcher. Hejl et al. (1995) notes that "sloppy " I clearcuts (some snags and trees remaining) or selection cuts may come the closest to mimicking these burns. Itmay also be necessary to include a range of sizes of harvested areas, and provide I attributes such as patches and strips of living trees within harvested areas (Bunnell 1995). A silvicultural system that provides live trees and snags within harvested areas is likely to be essential for management of the olive-sided flycatcher. I
On public lands, retention of some amount of standing, dead trees after a fire should be I maintained. Where salvage removal of standing, dead trees is to be conducted, Hutto (1995a) suggests that some areas remain uncut, rather than selective tree removal throughout the bum. In lieu of data on specific requirements of bum-associated species, this may minimize the I complete destruction of some microhabitats that may be essential for bum-associated species such as the olive-sided flycatcher. I Recent forest management practices seemingly beneficial to the olive-sided flycatcher include retention of snags and leave trees within clearcuts, and partial harvests via selective logging which I 38 I I I
I Table 4. Natural Heritage Program ranks and state/province listing status for breeding populations of the olive-sided flycatcher in western North America. I I Alaska S4 Species of Concern I Alberta S5 Arizona S4
I British Columbia S4 I California S4 Colorado S3/S4 ,, I Idaho S4 Manitoba S5
I Minnesota S? I Montana S4 Nevada S? I New Mexico S4 Oregon S4
I Saskatchewan S5 I Utah S3/S4 Washington S4/S5 I S4
a Categories and definitions: S3, rare or uncommon (2 1-100 occurrences); S4, apparently secure I with many occurrences (usually more than 100), but there is long-term concern for the species; S5, demonstrably secure; S3/S4, S4/S5, or S? indicate uncertainty about the status of the species. I I I 39 I I increase edge habitat and create a more open forest, yet retain substantial trees and snags. Hutto I (1995a) further suggests that an alternative to these traditional harvesting methods may be to subjectthe remaining harvested forest to a high-intensity bum. This would potentially create an ecosystem most similar in structure and function to that of one created under the natural I evolutionary process of stand-replacement fires. Selective cutting or burning that retains standing live or dead trees will likely provide suitable habitat for the olive-sided flycatcher. I
Within harvest units, retention of large snags or live trees should be considered in areas known to be occupied by olive-sided flycatchers. Data are not available to recommend the size of the I trees or snags, number to be retained, and spatial configuration. However, subjective observations indicate that 1) retention of trees of varying heights will likely provide the best opportunities for nesting sites, and 2) retention of trees near or above the canopy height of the surrounding forest I with extensive air space between the trees will likely provide adequate sallying space and height necessary for foraging olive-sided flycatchers . " , I i
The near absence of life history information on the olive-side flycatcher in migration and on its wintering grounds precludes establishment of specific management and conservation guidelines . I Until sound data are available on population levels, habitat selection and requirements, and factors affecting survivorship, conservation strategies are general guidelines such as the need for I preservation of montane tropical forest, particularly in the Andes Mountains . I RESEARCH AND MONITORING NEEDS
Clearly, more information isneeded on olive-sided flycatcher natural history, habitat relationships, I and other factors affecting its long-term viability . Given the magnitude, pervasiveness, and increasing rate of declines in olive-sided flycatcher populations, it is imperative that species I specific research be conducted to identify the factors contributing to these declines, and sound conservation and management strategies be developed. On the basis of information presented in this report, general focus areas for research should include 1) breeding season productivity and I associated environmental attributes across various habitats, landscapes, and forest management regimes; and 2) evaluation of the species status and ecology on the wintering grounds, including I the effect of forest alteration on wintering populations.
Breeding season research and monitoring may not need to focus on censusing, since population I data on the breeding grounds islikely adequately addressed through the BBS (and other large-scale censusing) . However, censusing maybe a necessary component of research designed to examine the effects . of forest management practices. As discussed previously, the most effective censusing I for olive-sided flycatchers would be unlimited distance point counts with a distance between points of at least 114 mile and preferably up to 112 mile (similar to the BBS). I 40 I· I I
I Research is needed in different habitat types throughout the species breeding range, but particularly in the Sierra Nevada and Cascade Mountain Ranges, where the species is experiencing its greatest declines, but is still relatively abundant enough to conduct large-scale studies. I Landscape scale research is likely to be most effective due to the species' relatively large territory size, and its propensity to be associated with edges at the interface of forest openings.
I To address the general research areas, the following approaches are suggested :
I 1. Comparison of olive-sided flycatcher productivity in various types of harvested forest, forest burns, and unmanaged forest. 2. Examination of habitat attributes and other factors (e.g., landscape features, food resources, I predation) associated with successful nesting in harvested forest, forest burns, -and unmanaged forest. I 3. Evaluation of habitat selection, resource use and competition, and the effects of habitat alteration and forest fragmentation on the wintering grounds. 4. Determination of nesting densities, habitat area requirements, and the relationships between I forest openings and forest edge within nesting territories in various forest types and landscapes. 5. Examination of prey availability and selection relative to nesting success to ascertain if food I resources are limiting productivity . 6. Long-term studies of marked populations to assess population dynamics, site fidelity , and survivorship in various forest types and landscapes. I I I I I I
I 41 I I
I
I LITERATURE CITED
Agee, J.K. 1991. Fire history of Douglas-fir forests in the Pacific Northwest. Pp.25-33 in L.F I Ruggiero, K.B. Aubry, A.B. Carey, and M.H. Huff (tech. coords.) Wildlife and vegetation of unmanaged Douglas-fir forests. USDA For. Serv. Gen. Tech. Rept. PNW- I 285. 533 pp. Alcorn, J.R. 1988. The birds of Nevada. Fairview West Publish ing, Fallon, Nevada. 418 pp. I Altman, B. in prep. Productivity of the olive-sided flycatcher in the Cascade Mountains of northern Oregon: a pilot project to assess nesting success as a potential factor in population I declines. Unpubl. rept submitted to U.S. Fish and Wildl. Serv., Oregon State Office, Portland. I American Ornithologist's Union. 1983. Check-list of North American birds. 6th ed. Allen-_:,-�,� I Press, Lawrence, Kansas. 877 pp. Apfelbaum, S. and A. Haney. 1981. Bird populations before and after wildfire in a Great Lakes I pine forest. Condor 83:347-354. Arendt, W.J. 1992. Status of North American migrant landbirds in the Caribbean region: a I summary . Pp. 143-174 in J.M. Hagan Ill and D.W. Johnston (eds.) Ecology and Conservation of Neotropical Migrant Landbirds. Smithsonian Institution Press, I Washington, D.C. 609 pp. Bailey, A.M. and R.J. Niedrach. 1965. Birds of Colorado. Vol. 2. Denver Museum of Natural I History . 895 pp.
Banks, R.C. and M.R. Browning. 1995. Comments on thestatus of revived old names for some I North American birds. Auk 112(3):633-648.
Barlow, C. 1901. A list of the landbirds of the Placervi11e-L�e Tahoe stage road. Condor I 3:151-184.
I Beedy, E. C. 19 81. Bird communities and forest structure in the Sierra Nevada of California. Condor 83:97- 105.
I Beal, F.E.L. 1912. Food of our more important flycatchers. U.S. Dept. Agr. Bioi. Surv. Bull. 44. I I 42 I I
Bendire, C. 1895. Life histories of North American birds: their breeding habits and eggs. I Smithsonian contributions to knowledge, No. 985. Smithsonian Inst., Washington D.C. 518 pp. I Bent, A. C. 1942. Life histories of North American flycatchers, larks, swallows and their allies. U.S. National Museum, Washington, D.C. 555 pp. I Blake, J.G. 1982. Influence of fr re and logging on nonbreeding bird communities of Ponderosa pine forests. J. Wildl. Manage. 46(2):404-415. I
Blake, J.G. and B.A. Loiselle. 1992. Habitat use by neotropical migrants at La Selva Biological Station and Braulio Carrillo National Park, Costa Rica. Pp. 257-272 in J.M. Hagan III I and D.W. Johnston (eds.) Ecology and Conservation of Neotropical Migrant Landbirds. Smithsonian Institution Press, Washington, D.C. 609 pp. _.:<�- I
Bock, C.E. and J.F. Lynch. 1970. Breeding bird populations of burned and unburned conifer forest in the Sierra Nevada. Condor 72 :182-189. I
Bonney, R. and D. Pashley 1994. Developing management objectives for neotropical migratory birds. Cornell Lab of Ornithology and The Nature Conservancy. Unpubl. draft paper. I Oct. 4, 1994. 7 pp. I Brewester, W. 1906. The birds of the Cambridge regionof Massachusetts. Nuttall Ornithol. Club Memoirs 4, Cambridge, MA. I Bryant, D.M. 1975. Breeding biology of house martins Delichon urbica in relation to aerial insect abundance. Ibis 117:180-216. I
Buckner, C.H . , A.J. Erskine, R. Lidstone, B.B. McLeod, and M. Ward. 1975. The breeding bird community of northern Vancouver Island. The Murrelet 56(3):6-1 1. I Bunnell, F.L. 1995. Forest-dwelling vertebrate faunas and natural fire regimesin British Columbia: patterns and implications for conservation. Conserv. Bioi. _9(3):636-644. I Burleigh, T.D. 1972. · Birds ofldaho. CaxtonPrinters Ltd., Caldwell, Idaho. 467 pp.
Burns,F.L. 1915. Comparative periods of deposition and incubation of some North American birds. I Will. Bull. 27:275-286.
Bystrak, D. 1981. The North American Breeding Bird Survey. Pp. 34-41 in C.J. Ralph and J.M. I Scott (eds.) Estimating numbers of terrestrial birds. Studies in Avian Bioi. No. 6. I 43 I I I
Canaday, C. 1997. Loss of insectivorous birds along a gradient of human impact inAmazoni a. Biol. · I Cons. 77:63-77. I Cannings, R.A., R.J. Cannings, and S.G. Cannings. 1987. Birds ofthe Okanagan Valley, British Columbia. Royal British Columbia Museum, Victoria, B.C. 420 pp.
I Carey, A.B., M.M. Hardt, S.P. Horton, and B.L. Biswell. 1991. Spring bird communities in the Oregon Coast Range. Pp. 123-144 in L.F. Ruggiero, K.B. Aubry, A.B. Carey, and M.H. Huff(tech. coords.) Wildlife and vegetation of unmanagedDouglas-fir fo rests. USDA, For. I Serv. Gen. Tech. Rept. PNW-285.
Carter, M.F. and K. Barker. 1993. An interactive database fo r setting conservation priorities fo r I westernneot ropical migrants. Pp. 120-144 in D.M. Finch and P. W. Stangel ( eds.) Status and management ofneotropical migratory birds. USDA, For. Serv. Gen. Tech. Rept. RM-229. I 422 pp. Cheskey, T. 1987. Olive-sided flycatcher. Pp. 250-251 in M.D. Cadman, P.F.J. Eagles, and F.M. -_::,...- �co:.,,; . Helleiner (eds.) Atlas of the breeding birds of Ontario. Fed. OntarioNa t., Univ. Waterloo I Press, Waterloo, Ontario.
Courson, D., C.B. Goguen, and N.E. Mathews. 1996. Nest site reuse in western wood-pewees. I Wil. Bull. 108(2):378-379. I Cross, S.P. and J. K. Simmons. 1983. Bird populations of the mixed-hardwood fo rests near Roseburg, Oregon. Oreg. Dept. Fish and Wild!., Tech. Rept. 82-2-05. 41 pp.
I Davies, N.B. 1977. Prey selection and the search strategy ofthe spotted flycatcher (Muscicapa struata): a fieldstudy on optimalfo raging. Anim. Behav. 25: 1016-103 3.
I Davis, D.E. 1954. The breeding biology ofthe Hammond'sflyca tcher. Auk 71:161-174.
Davis, J., G.F. Fisler, andB.S. Davis. 1963. The breeding biology of the western flycatcher. I Condor 65:337-382.
Davis, P.R. 1976. Response of vertebrate fauna to fo rest fire and- clearcutting in southcentral I Wyoming. PhD, Univ. Wyoming, Laramie.
Degraaf, R.M. and J. H. Rappole. 1995. Neotropical migratory birds: natural history, distribution; I and population change. Comstock Publishing Associates, Ithaca, NY. 676 pp.
Derleth, E.L., D. G. McAuley, and T.J. Dwyer. 1989. Avian community response to small-scale I habitat disturbance in Maine. Can. J. Zool. 67:385-390. I DeSante, D.F. and T.L. George. 1994. Population trends in the landbirds ofwestern North America. 44 I I I
Pp. 173-190 in J.R. Jehl, Jr. and N.K. Johnson (eds.) A century of avifaunal change in I westernNorth America. Studies in Avian Biology, No. 15, Cooper Om. Soc. 348 pp. Diamond, A. W. 1991. Assessment of the risks fromtropical deforestation to Canadiansong birds. I Trans. 56th N. Amer. Wildl. and Nat. Res. Conf 177-194.
Dixon, J. 1920. Nesting of the olive-sided flycatcher in Berkeley, California. Condor 22:200-202. I
Droege, S. 1990. The North American Breeding Bird SUIVey. Pp. 1-4 in J.R. Sauer andS. Droege (eds.) SUIVey designs and statistical methods for the estimation of avian population trends. I U.S. Fish and Wildl. Serv. Bioi. Rept. 90(1).
Duncan, R.A. 1988. The olive-sided flycatcher, a rare but regular migrant in northwest Florida. I Florida Field Nat. 16:72-74. I Dunn, E.H. 1991. Population trends in Canadian songbirds. Bird Trends 1 :2-11. _::.::.��. ':z:/•Jf::-- . ·.. :- . Dunn, E.H. and D.J.T. Russell. 1995. Using migration counts to monitor landbird populations: I review andevaluation of current status. Pp. 43-88 in D.M. Power (ed.) Current Ornithology, Vol. 12. Plenum Press, New York. I Dwight, J. 1900. The sequence of plumages and moults of the passerine birds of New York. Annals of the New York Acad. Sci. 13(2):73-360. I· Eckhardt, R.C. 1976. Polygyny in the westernwood-pew ee. Condor 78:561-562.
Eckhardt, R.C. 1979. The adaptive syndromes of two guilds ofinsectivorous birds in the Colorado I Rocky Mountains. Ecol. Mono. 49(2):129-149.
Edwards, B.F. 1973. Report on the avifauna ofthe Vermilion Pass burnarea. Unpubl. rept., Parks I Canada, Calgary, Alberta. 27 pp.
Ehrlich, P.R., D.S. Dobkin, and D. Wheye. 1988. The birder's handbook. Simon and Schuster Inc., I New York. 785 pp.
Erskine, A.J. 1977. Birds in Boreal Canada: communities, densities, and adaptations. Canadian I Wildl. Serv. Rept. Series No. 41. 73 pp. I Erskine, A.J. 1992. Olive-sided flycatcher, Contopus borealis. Pp 114 in A.J. Erskine (ed.)? Atlas of breeding birds of the Maritime Provinces. Nimbus Publishing Limited and Nova Scotia Museum, Novea Scotia. I Evans, D.M. and D. M. Finch. 1994. Relationships between forest songbird populations and I 45 I I I
managed fo rests inIdaho . Pp. 308-314 in W.W. Covington and L.F. DeBano (tech. coords.) I Sustainable ecological systems: implementing an ecological approach to land management. USDA For Serv. Gen Tech. Rept. RM-247. 363 pp. I ffr ench, R. 1991. A guide to the birds of Trinidad and Tobago. Comstock Publishing Assoc., Ithaca, New York. 426 pp. I Fichte� C. 1985. Olive-sidedflycatcher, Contopus borealis. Pp. 170-171 in S.B. Laughlin and D.P. Kibbe (eds.) The atlas ofbreeding birds of Vermont. Univ. Press ofNew England, Hanover, I New Hampshire. 456 pp.
Finch, D.M. 1992. Threatened, endangered, and vulnerable species of terrestrial vertebrates in I the Rocky Mountain Region. USDA, Forest Service, Gen . Tech. Rept. RM-215. 38 pp.
I Finch, D.M. and R.T. Reynolds. 1988. Bird response to understory variation and conifer succession in aspen forests. Pp. 87-96 in Issues and Technology in the Management of _ ---'-',_�,;; . I Impacted Western Wildlife, Symp. Proc . Thorne Ecological Institute, Boulder, CO Fischer, W.C. and A.F. Bradley. 1987. Fire ecology of western Montana forest habitattypes. I USDA For. Serv . Gen. Tech. Rept. INT-223.
Fitzpatrick, J.W. 1978. Foraging behavior and adaptive radiation in the avian family I Tyrannidae. Unpubl. PhD. dissertation. Princeton University, Princeton, New Jersey . · · 138 pp.
I Fitzpatrick, J. W. 1980. Wintering of North American tyrant flycatchers in the neotropics. Pp. 67-78 in A. Keast and E;S. Morton (eds.) Migrant birds in the neotropics: ecology, I behavior, distribution, and conservation. Smithsonian Inst. Press, Washington D.C. 576 pp.
I Francis, J. and K. Lumbis. 1979. Habitat relationships and management of territorial birds in northeastern Alberta. Alberta Oil Sands Environmental Research Program, Project LS I 22. 1.1. September 1979. 365 pp.
Franzreb , K.E. 1977. Bird population changes after timber harvesting of a mixed conifer forest I in Arizona. USDA For. Serv. Res. Paper RM-184. 25 pp.
Franzreb, K.E. and R.D. Ohmart. 1978. The effects of timber harvesting on breeding birds in I a mixed-coniferous forest. Condor 80:431-441.
I Friedmann, H. 1934. Further additions to the list of birds victimized by the cowbird. Wilson 46 I I I Bull. 46:25-36. I Friedmann, H. 1963. Host relations of the parasitic cowbirds. U.S. Nat. Mus. Bull. No. 233. I Friedmann, H., L.F. Kiff, and S.I. Rothstein. 1977. A further contribution to knowledge of the host relations of the parasitic cowbirds. Smithsonian Contributions to Zoology, No. 235. Smithsonian Inst. Press, Washington D.C. I
Gabrielson, LN. and F.C. Lincoln. 1959. Birds of Alaska. Stackpole Co. andWildl . Manage. I lnst., Harrisburg, Pennsylvania. 922 pp.
Gabrielson, I.N. and S.G. Jewett. 1970. Birds ofthe PacificNorth west. Dover reprint, New York. I 650 pp.
Garrett, K. and J. Dunn. 1981. Birds of southern California. Los Angeles Aud. Soc., Los - .:�=-�-= "'· I _ Angeles, CA. 408 pp. I Geissler, P.H. and J.R. Sauer. 1990. Topics in route-regression analysis. Pp. 54-57 in J.R. Sauer and S. Droege (eds.) Survey designs and statistical methods for theestimation of avian population trends. U.S. Fish and Wildl. Serv. Bioi. Rept. 90(1). I Gibson, D.D. andS.O. MacDonald. 1975. Bird species and habitat inventory, Alexander I Archipelago, Alaska, summer 1975. Univ. Alaska Museum rept. to USFS.
Gilligan, J, M. Smith, D. Rodgers, and A. Contreras. 1994. Birds of Oregon: Status and I Distribution. Cinclus Publications, McMinnville. 330 pp.
Godfrey, W.E. 1979. The birds of Canada. Nat. Mus. Natural Sci., Ottawa. 428 pp. I
Godfrey, W.E. 1986. Birds of Canada. National Museum ofNatural Sciences, National Museums ofCanada. 595 pp. I
Granholm, S.L. 1982. Effects of surface frr es on birds and their habitat associations in I coniferous forests of the Sierra Nevada, California. Unpubl. PhD. dissertation. Univ. of Calif. , Davis. 130 pp . I Grinnell, J. and A.H. Miller. 1944. The distribution of the birds of California. Pac. Coast Avifauna No. 27. 608 pp. I
Grinnell, J. and T.I. Storer. 1924. Animal life in Yosemite: an account of mammals, birds, I 47 I I I
I reptiles a, and amphibians in a cross section of the Sierra Nevada. Univ. Calif. Press, Berkeley. 752 pp.
I Gruell, G.E. 1983. Fire and vegetative trends in the Northern Rockies: interpretations from 1871-1982 photographs. USDA For. Serv. Gen. Tech. Rept. INT-150. I Hagar, D.C. 1960. The interrelationships of logging, birds, and timber regeneration in the I Douglas-frr region of northwestern California. Ecology 41(1):116-125. Hamilton, R.A. and D.R. Willick. 196. The birds of Orange County, California: status and I distribution. Sea and Sage Press, Irvine. Harrison, H.H. 1975. A field guide to birds' nests. Houghton Mifflin Co., Boston. 257 pp. 'I Head, A. 1903 . Nesting habits of two flycatchers at Lake Tahoe. Bird-Lore 5:153-155.
I Heinselman, M.L. 1973. Fire in the virgin forests of the Boundary Waters canoe area, Minnesota. Quat. Res. 3:329-382. I Hejl, S.J. 1994. Human-induced changes in bird populations in coniferous forests in western
North America during the past 100 years. Pp. 232-246 in I.R. Jehl, Jr. and N.K. Johnson I (eds.) A century of avifauna! change in westernNorth America. Studies in Avian Biology, , No. 15, Cooper Om. Soc. 348 pp.
I Hejl, S.J. and L.C. Paige. 1994. A preliminary assessment of birds in continuous and fragmented fo rests ofwestern redcedar/ westernhemlock in northernIdaho . Pp. 189-197 in Proc. Interior Cedar-Hemlock-WhitePine Forests: Ecology and Management. Dept. Nat. Res. Sc., Wash. I State Univ., Pullman.
Hejl, S.J., I. Verner, and R.P. Balda. 1988. Weather and bird populations in true-firfo rests ofthe I SierraNevada, California. Condor 90:561-574. I Hejl, S.J., R.L. Hutto, C.R. Preston, and D.M. Finch. 1995. Effects of silvicultural treatments in the Rocky Mountains. Pp. 220-244 in T. E. Martin and D.M. Fich (eds.) Ecology and management of neotropical migratory birds; a synthesis and review of critical issues. Oxford I Univ. Press. 409 pp.
Hilty, S.L. 1980. Relative abundance of north temperate zone breeding migrants in western I Columbia andtheir impact at fruitingtrees. Pp. 265-272 in A. Keast and E.S. Morton (eds.) Migrant birds in the neotropics: ecology, behavior, distribution, and conservation. I Smithsonian Inst. Press, Washington D.C. 576 pp. I 48 I
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Hilty, S.L. and W.L. Brown. 1986. A guide to the birds of Columbia. Princeton Uruv. Press, I Princeton, NJ. 836 pp.
Hink:es, M. T. and K.T. Engel. 1981. Bird communities of recently burned and unburned forest and I scrublandhabitat s in interior Alaska. Bureau of Land Manage., Anchorage District. 38 pp.
Holroyd, G.L. and K.J. VanTighem. 1983. The ecological (biophysical) land classification ofBanff I and Jasper National Parks: Volume ill, the wildlife inventory. Canadian Wildl. Serv., Edmonton. 444 pp. I Howell, S.N.G. and S. Webb. 1995. A guide to the birds ofMexico and northernCe ntral America. Oxford Univ. Press, New York. 851 pp. I
Horvath, 0. 1963. Contributions to nesting ecology of forest birds. M.F. Thesis, Univ. ofBritish Columbia. 181 pp. - I -_::.!.��- . !!!:"-:'':.if·-'< Hutto, R.L. 1995a. Composition ofbird communities fo llowing stand-replacement fires in northern Rocky Mountain fo rests. Conserv. Biol.9(5):1041-1058. I
Hutto, R.L. 1995b. USFS Northern Region songbird monitoring program: distribution and habitat relationships. Contract report to USFS Region 1. Nov. 1995. 120 pp. I Imhof, T.A. 1976. Alabamabirds. Univ. of Alabama Press. 445 pages. I Jenks. 1934. Unusual nesting records fromnorthern Arizona. Condor 36:172-176.
Jewett, S.G., W.P. Taylor, W.T. Shaw, and J.W. Aldrich. 1953. Birds ofWashington State. Univ. I Washington Press, Seattle. 767 pp.
Johnson, N.K. 1965a. Differential timing and routes of the spring migration in the Hammond's I flycatcher. Condor 67:423-437. I Johnson, N.K. 1965b. The breeding avifaunas ofthe Sheep and SpringRan ges in southernNevad a. Condor 67(2):93-124. I Johnson, N.K. and C. Cicero. 1985. The breeding avifauna of San Benito Mountain, California: evidence fo r change over one-half century. WesternBirds 16(1): 1-23 . I Johnson, T.B. 1980. Resident and North American migrant bird interactions in the Santa Marta highlands, northern Columbia. Pp. 239-248 in A. Keast and E.S. Morton (eds.) Migrant birds in the neotropics: ecology, behavior, distribution, and conservation. Smithsonian I Inst. Press, Washington D.C. 576 pp . I 49 I I I
I Johnston, D.W. 1949. Populations and distribution of summer birds of Latah County, Idaho. Condor 51:140-149.
I Johnston, D.W. 1971. Niche relationships among some deciduous fo rest flycatchers. Auk 88:796- 804.
I Kessel, B.K. and D.D. Gibson. 1978. Staus and distribution of Alaska birds. Studies in Avian Biology, No. 1, Cooper Ornithological Society, Allen Press, Lawrence, Kansas. 100 pp.
I Kilgore, B.M. 1971. Response of breeding bird populations to habitat changes in a giant sequoia fo rest. Am. Midi. Nat. 85: 135-152.
I Lack, D. andE. Lack. 195 1. The breeding biology of the swift, Apus ap us. Ibis 91:64-88. · I Land, H. C. 1970. Birds of Guatemala. Livingston Publishing Co., Wynnewood, Penna. 381 pp. - :, - ·· - Lehman, P.E. 1994. The birds of Santa Barbara County, California. Univ. Calif Santa Barbara _.: �=� · I Vertebrate Museum. SantaBarbara. 337 pp. LeGrand, HE. Jr. and S.P. Hall. 1989. Element stewardship abstract - Contopus borealis. The I nature Conservancy, Arlington, Virginia. Ligon, J.S. 1961. New Mexico birds and where to find them. Univ. of New Mexico Press. 360 pp. I Lowe, P.O., P.F. Ffolliott, J.H. Dieterich, and D.R. Patton. 1978. Determining potential wildlife benefits fromwildfire in Arizona Ponderosa pine fo rests. USDA For. Serv. Ge, Tech. Rept. I RM-52. 12 pp.
Mannan, R.W. 1984. Habitat use by Hammond's flycatcher in old-growth fo rests, northeastern I Oregon. Murrelet 65:84-86.
Marshall, J.T. 1988. Birds lost froma giant sequoia fo rest during fiftyyears . The Condor 90:359- I 372.
Martin, T.E. 1987. Interaction of nest predation and fo od limitation- in reproductive strategies. I Curr. Ornith. 9:163-197.
McGarigal, K. andW.C. McComb. 1995. Relationships between landscape structure and breeding I birds in the Oregon Coast Range. Ecol. Mono. 65(3):235-260. I Mearns, E.A. 1890. Observations on the avifauna of portions of Arizona. Auk 7:251-264. Medin. D.E. 1985a. Densities and nesting heights of breeding birds in an Idaho Douglas-firfo rest. I Northwest Sci. 59(1):45-52. I 50 I I
Medin, D.E. 1985b. Breeding bird responses to diameter-cut logging in west-central Idaho. USDA, I Forest Service, Intermountain Research Station, Research Paper INT-355. 12 pp. I Medin, D.E. and G.D. Booth. 1989. Responses of birds and small mammals to single-tree selection logging in Idaho. USDA, Forest Service, Intermountain Research Station, Research Paper INT-408. 11 pp. I Meyer de Schauensee, R.M. and W.H. Phelps Jr. 1978. A guide to the birds of Venezuela. Princeton Univ. Press, Princeton, N.J. 424 pp. I
Miller, A.H. 1963. Seasonal activity and ecology ofthe avifauna of an American equatorial cloud fo rest. Univ. Calif Publ. Zool. 66(1 ): 1-78. Univ. Calif Press, Berkeley. I
- Monroe, B.L. Jr. 1968. A distributional survey of the birds of Honduras. Ornithological - Monograph No. 7. American OrnithologicalUn ion. 458 pp. I �_..: .!���·�"'
Morrison, M.L., K.A. With, and I.C. Timossi. 1986. The structure of a forest bird community during winter and summer. Wilson Bulletin 98(2):214-230. I Mueller, A. J. 1993. Bottomland hardwood forest habitat goals and objectives for neotropical I migratory birds in the east Gulf Coast Plain physiographic area. U .F. Fish and Wildl. Serv., unpubl. draftpa per. Nov. 1993. 14 pp . I Murphy, M.T. 1983a. Nest success and nesting habits of eastern kingbirds and other flycatchers. Condor 85:208-219. I Murphy, M. T. 1983b. Clutch size in the easternkingb ird: factors affecting nestling survival. Auk 100:326-334. I Murphy, M. T. 1989. Life history variability in North American breeding tyrant flycatchers: phylogeny, size or ecology. Oikos 54:3-14. I Myers, N. 1985. Comparison oftwo recent estimates of disturbancein tropical fo rests. Environ. Cons. 12:37-40. I O'Hara, K.L., R. S. Semour, S.D. Tesch, and J.M. Guldin. 1994. Silviculture and our changing profession: leadership fo r shifting paradigms. J. ofForestry 92:8-13. I Orejuela, J.E. 1985. Tropical fo rest birds of Columbia: a survey of problems and a plan fo r their conservation. Pp. 95-114 in A.W. Diamond and T.E. Lovejoy (eds.) Conservation of tropical I fo rest birds. ICBP Tech. Publ. No. 4, Paston Press, Norwich, U.K. I 51 I I I
I Otvos, I.S. and R.W. Stark. 1985. Arthropod fo od of some fo rest-inhabiting birds. Can. Ent. 117:971-990.
I Overturf,J.H. 1979. The effectsof fo rest fire onbreeding bird populations of ponderosa pine fo rests of northern Arizona. Unpubl. MS thesis. Northern Ariz. Univ., Flagstaff. 108 pp.
I Paynter, R.A. Jr. 1995. Nearctic passerine migrants in South America. Publ. ofthe Nuttall Ornith. Club, No. 25. Cambridge, MA. 126 pp.
I Pearson, D.L. 1980. Bird migration in AmazonianEcuador, Peru, and Bolivia. Pp. 273-284 in A. Keast and B.S. Morton (eds.) Migrant birds in the neotropics: ecology, behavior, I distribution, and conservation. Smithsonian Inst. Press, Washington D.C. 576 pp. Petetjohn, B. G. and J.R. Sauer. 1994. Population trends of woodland birds from the North I AmericanBreeding Bird Survey. Wildl. Soc. Bull. 22:155-164.
Petetjohn, B. G., J.R. Sauer, and C.S. Robbins. 1995. Population trends from the North American I Breeding Bird Survey. Pp. 3-39 in T.E. Martin and D.M. Finch (eds.) Ecology and management ofNeotropical migratorybirds; a synthesis and review of critical issues. Oxford I Univ. Press, New York. 489 pp. Peterson, J.M.C. and C. Fichtel. 1992. Olive-sided flycatcher, Contopus borealis. Pp. 353-367 in K.J. Schneider and D.M. Pence (eds.) Migratory nongamebirds of management concern in I the northeast. U.S. Fish and Wildt. Serv., Newton Comer, Mass. 400 pp.
Peterson, R.T. 1980. A field guide to the birds east ofthe Rockies. 4th ed. Houghton Mifflin Co., I Boston. 384 pp. I Peterson, R.T. 1990. A field guide to westernbirds. Houghton Mifflin Co., Boston. 432 pp.
Peterson, S.R. 1982. A preliminary surveyof fo restbird communities in northern Idaho. Northwest I Science 56(4):287-298. Petit, D.R., J.F. Lynch, R.L. Hutto, J.G. Blake, and R.B. Waide. 1993. Management and I conservation of migratory landbirds overwintering in the neotropics. Pp. 70-92 in D.M. Finch and P.W. Stangel (eds.) Status and management of neotropical migratory birds. USDA For. I Serv. Gen. Tech. Rept. RM-229. 422 pp. Petit, D.R., J.F. Lynch, R.L. Hutto, J.G. Blake, and R.B. Waide. 1995. Habitat use and conservation in the neotropics. Pp. 145-197 in T.E. Martin and D.M. Finch (eds.) Ecology I and management of neotropical migratory birds; a synthesis and review of critical issues. Oxford Univ. Press. 409 pp. I I 52 I I
Pfister, A.R. 1980. Postfire avian ecology in Yellowstone National Park. Unpubl. M.S. Thesis, Wash. State Univ, Pullman. 35 pp. I Phillips, A.R. 1936. A nest ofthe olive-sided flycatcher. Condor 39:92. I Phillips, A., J. Marshall, and G. Monson. 1964. The birds of Arizona. Univ. of Arizona Press, Tucson. 212 pp. I Pyle, P., S.N.G. Howell, R.P. Yunick, and D.F. DeSante. 1987. Identification guide to North Americanpasserines. Slate Creek Press, Bolinas, California. 278 pp. I
Pyle, P., N. Nur, and D.F. DeSante. 1994. Trends in nocturnal migrant landbird populations at Southeast Farallon Island, California, 1968-1992. Pp. 58-74 in J.R. Jehl, Jr. and N.K. I Johnson (eds.) A century ofavifaunal change in western North America. Studies in Avian Biology, No. 15, Cooper Ornith. Soc. 348 pp. I __:!------.z::::�-�
Quinlan, S.E. 1979. Effects of controlled burning and succession of white spruce fo rests on breeding bird communities, Kenai Peninsula, Alaska. Unpubl. rept to Chugach Nat. For., I Seward Ranger District. 53 pp.
Raphael, M.G. 1984. Wi ldlife populations in relation to stand age and area in Douglas-fir fo rests of I northwestern California. Pp. 259-274 in W.R. Meehan, T.R. Merrell, Jr., and T.A. Hanley (eds.) Fish and wildlife relationships in old-growth fo rests. Symp. Proc., Amer. Inst. Fish. Res. Bioi. 425 pp. 'I Raphael, M.G. 1987. Nongame wildlife research in subalpine fo rests of the central Rocky I Mountains. Pp. 113-"122 in ? (ed.) ? USDA For. Serv. Gen. Tech. Rept. RM-149.
Raphael, M.G., M.L. Morrison, and M.P. Yoder-Williams. 1987. Breeding bird populations during I twenty-five years ofpostfiresuccession in the Sierra Nevada. Condor 89:614-626.
Raphael, M.G., K.V. Rosenberg, and B. G. Marcot. 1988. Large-scale changes in bird populations I ofDouglas-fir fo rests, northwestern California. Bird Conserv. 3:63-83.
Reed, J.M. 1995. Relative vulnerability to extirpation ofmontane breeding birds in the Great Basin. ,I Great Basin Nat. 55(4):342-351.
Ridgely, R.S. 1976. A guide to the birds ofPanama. Princeton Univ. Press, Princeton, New Jersey. I 393 pp.
Ridgely, R.S. and J.A. Gwynne Jr. 1989. A guide to the birds of Panama. Princeton Univ . I Press, Princeton, NJ. 534 pp. I 53 I I I I Ridgely, R.S. and G. Tudor. 1994. The birds of South America: Volume II, the suboscine passerines. Univ. of Texas Press, Austin. 814 pp.
I Ridgeway, R. 1887. Manual of North American Birds.
Robbins, C.S., D. Bystrak, and P.H. Geissler. 1986. The Breeding Bird Survey: its fr rst fifteen I years, 1965-1979. U.S. Dept. Interior, Fish and Wildl. Serv. Res. Publ. 157.
I Robbins, C.S., J.R. Sauer, R.S. Greenberg, and S. Droege. 1989. Population declines in North American birds that migrate to the neotropics. Pp. 7658-7662 in Proc. Natl. Acad. Sci., I Vol. 86, Oct. 1989. Robbins, C.S., J.W. Fitzpatrick, and P. Hamel. 1992. A warbler in trouble: Dendroica cerulea. Pp. 549-562 in J.M. Hagan, III and D.W. Johnston (eds.) Ecology and conservation of I Neotropical migrant landbirds. Smithsonian Instit. Press, Wash., D.C. �_: !:�,��- � I Roberts, T.S. 1932. The birds ofMinnesota. Vol. II. Univ. ofMin. Press, Minneapolis. 821 pp. Robinson, S.K., J. Terborgh, and J.W. Fitzpatrick. 1988. Habitat selection and relative abundance I of migrants in southeastern Peru. Proc. XIX Intematn. Om. Congr. :2298-23 11.
Robinson, S.K., J.W. Fitzpatrick, and I. Terborgh. 1995. Distnbution and habitat use ofNeotropical I migrant landbirds in the Amazon basin and Andes. Bird Conserv. Internatn. 5:305-323.
Robins, J.D. 1970. The relationship of food supply to the timing of breeding in aerial foragers. I Kansas Ornith. Soc. Bull. 21:9-15. I Rosenberg, K.V. and M.G. Raphael. 1986. Effects of forest fragmentation on vertebrates in Douglas-fir forests. Pp. 263-272 in J. Verner, M. Morrison, and C.J. Ralph (eds.) Modeling habitat relationships of terrestrial vertebrates. Univ . of Wisconsin Press, I Madison. 470 pp.
Ruggerio, L.F., L.C. Jones, and K.B. Aubry. 1991. Plant and animal associations in Douglas I fir forests of the Pacific Northwest:an overview. Pp. 447-462 in L.F. Ruggerio, K.B. Aubry, A.B. Carey, and M.H. Huff (tech. coordinators), Wildlife and vegetation of I unmanaged Douglas-frr forests. USDA, Forest Service, Gen. Tech. Rept. PNW-GTR- 285.
I Russell, S.M. 1964. A distributional study of the birds of British Honduras. Ornithological MonographsNo. 1. American Ornithological Union. 195 pp. I 54 I I I
Saab, V. and T. Rich. in press. Large-scale conservation assessment fo r neotropical migratoryland birds in the Interior Columbia River Basin. USDA, For. Serv. Gen. Tech. Rept. PNW-GTR I XXX. Portland, OR.
Sakai, H.F. 1988. Breeding biology and behavior of Hammond's and western flycatchers in I northwestern California. Western Birds 19(2):49-60. I Sallabanks, R. 1995. Bird-habitat relationships in industrial fo rested landscapes of the inland northwest: pilot studies in Idaho and Oregon. Unpubl. ann. rept, Sustainable Ecosystems Institute, Meridian, ID. 74 pp. I
Sallabanks, R. 1996. Avian biodiversity and bird-habitat relationships in conifer fo rests ofthe Inland Northwest: an ecosystem management approach. Unpubl. ann. rept., Sustainable Ecosy-stems I Institute, Meridian, ID. 150 pp.
Salt, W.R. and J.R. Salt. 1976. The birds of Alberta; with their ranges in Saskatchewan and I - ___::.!:��!� "' Manitoba. Hurtig Publishers, Edmonton. 498 pp.
Sauer, J.R. and S. Droege. 1992 . Geographic patterns in population trends of neotropical I migrants in North America. Pp. 26-42 in J.M. Hagan III and D.W. Johnston (eds.), Ecology and conservation of neotropical migratory landbirds. Smithsonian Institution I Press, Washington D.C., 609 pp.
Sauer, J.R., B.G. Peterjohn, and W.A. Link. 1994. Observer differences in the North American I Breeding Bird Survey. Auk 111:50-62. I Sauer, J.R., J.E. Hines, G. Gough, I. Thomas, andB.G. Peterjohn. 1997 . The North American Breeding Bird Survey: results and analysis. Version 96.3. Patuxent Wildlife Research Center, Laurel, MD. I
Schieck, J. and M. Nietfeld. 1995 . Bird species richness and abundance in relation to stand age and structure in aspen mixedwood fo rests in Alberta. Pp. 115-157 in J.B. Stelfox (ed.) I Relationships between stand age, stand structure, and biodiversity in aspen mixedwood fo rests in Alberta. Alberta Env. Center, Vegreville, and Canadian For. Serv., Edmonton. I 308 pp .
Scott, V.E. and G.L. Crouch. 1987. Response of breeding birds to commercial clearcutting of I aspen in southwestern Colorado. USDA For. Serv . Res. Note RM-475. 5 pp. I Scott, V.E. and G.L. Crouch. 1988. Summer birds and mammals of aspen-conifer fo rests in west-central Colorado. USDA For. Serv. Res. Paper RM-280. 6 pp . I
55 I I I
Scott, V.E., G.L. Crouch, and J.A. Whelan. 1982. Response of birds and small mammals to I clearcutting in a subalpine forest in central Colorado. USDA, Forest Service, Research
Note RM-422. 6 pp. I Sedgwick, J.A. 1993. Reproductive ecology of the dusky flycatcher in westernMontana. Wilson I Bull. 105:84-92. Sherry, T.W. 1984. Comparative dietary ecology of sympatric, insectivorous neotropical flycatchers I (Tyrannidae). Ecol. Mono. 54(3):313-338. Shuford, W.D. 1993. Olive-sided flycatcher, Contopus borealis. Pp. 255-256 in W.D. Shuford (ed.) The Marin County breeding bird atlas: a distributional and natural history of coastal I Californiabirds. CaliforniaAvif auna! Series No. 1, Bushtit Books, Bolinas; CA. 479 pp. I Smith, C.P. 1927. The olive-sided flycatcher and coniferous trees. Condor 29: 120-121. Snyder, D.P. 1950. Bird communities in the coniferous fo rest biome. Condor 52:17-27. I Spindler, M.A. and B. Kessel. 1980. Avian populations and habitat use in interior Alaska taiga. I Syesis 13:61-104. Sprunt, A. Jr. 1954. Florida bird life. Coward-McCann Inc., and National Audubon Society, New I York. 527 pp.
Stevens, L.E., B.T. Brown, J.M. Simpson, and R.R. Johnson. 1977. The importance of riparian I habitat to migrating birds. Pp. 156-164 in Importance, preservation, and management of riparian habitat: a symposium. USDA For. Serv. Gen. Tech. Rept. RM-43 .
I Stiles, E.W. 1980. Bird community structure in alder fo rests ofWashington. Condor 82:20-30.
Stiles, G.F. 1980. Evolutionary implications of habitat relations between permanent and winter I resident landbirds in Costa Rica. Pp. 421- 43 6 in A. Keast and E. S. Morton (eds .) Migrant birds in the neotropics: ecology, behavior, distribution, and conservation. Smithsonian I Inst. Press, Washington D.C. 576 pp. Stiles, G.F. 1994. A study of fal l migration ofNearctic-breeding landbirds in central Costa Rica. I Bird Conserv. Intematn. 4:71-89.
Stiles, F.G. andA.F. Skutch. 1989. A guide to the birds of Costa Rica. Comstock Publishing I Assoc., Ithaca, New York. 511 pp. I Stotz, D.F., R.O. Bierregaard, M. Cohn-Haft, P. Petermann, J. Smith, A. Whittaker, and S.V. 56 I I II I Wilson. 1992. The status ofNorth American migrants in central AmazonianBrazil . The Condor 94:608�621. I
Stotz, D.F., J.W. Fitzpatrick, T.A. Parker, and D.K. Moskovits. 1996. Neotropical birds: ecology and conservation. Univ. of Chicago Press, Chicago. 478 pp. I
Swainson, W. and Richardson, J. 1831. Fauna Boreali-Americana. Vol. 2, Birds. I
Taverner, P.A. 1928. Birds of western Canada. Canada Department of Mines and National Museum of Canada. Bull. No. 41, Bioi. Series No. 10. Ottawa. 379 pp. I
Taylor, D.L. andW.J. Barmore Jr. 1980. Post-fire succession of avifauna in coniferous forests of Yellowstone and Grand Teton National Parks, Wyoming. Pp. 0-13 145 in R.M. I DeGraff(tech coord.) Management of western forests and grasslands for nongame birds. USDA For. Serv. Gen Tech. Rept. INT-86. 535 pp. I ·· !:--.....-..-� ::£ ··
Terborg, J.W. 1980. The conservation status of neotropical migrants: present and future . Pp. 21-30 in A. Keast and E.S. Morton (eds.) Migrant birds in the neotropics: ecology, I behavior, distribution, and conservation. Smithsonian Inst. Press, Washington D.C. 576 pp. I
Terres, J.K. 1987. The Audubon Society encyclopedia of North American birds. Alfred A. Knopf Inc., New York. 1,109 pp. I
Theberge, J.B. 1976. Bird populations in the Kluane Mountains , southwest Yukon, with special reference to vegetation and fire. Can. J. Zool. 54: 1346-1356 I
Thomas, L. andK. Martin. 1996. The importance of analysis method for breeding bird survey I population trend estimates. Conserv. Biol.10(2):479-490.
Tobalske, B.W., R.C. Shearer, and R.L. Hutto . 1991. Bird populations in logged and unlogged I western larch/Douglas-fir forest in northwestern Montana. USDA For. Serv . Res. Paper INT-442. 12 pp . I
Turchi, G.M., P.L. Kennedy, D. Urban, and D. Hein. 1995. Bird species richness in relation to isolation of aspen habitats. Wilson Bull . 107(3):463-474. I
U.S. Department of the Interior. 1994. Endangered and threatened wildlife and plants; animal candidate review for listing as endangered or threatened species; proposed rule. Federal I register, Tuesday, November 15, 1994. I 57 I I I I U.S. Department of the Interior. 1996. Endangered and threatened wildlife and plants; review of plant and animal taxathat are candidates for listing as endangered or threatened species. Federal register, Vol 61, No. 40. Wednesday, February 28, 1996. I U.S. Fish and Wildlife Service. 1988. Nongame bird strategies. Office of Migratory Bird I Management, U.S. Fish and Wildlife Service, Washington, D.C. May 1988. U.S. Fish and Wildlife Service. 1995. Migratory nongame birds of management concern in the I continental United States: the 1995 list. Office of Migratory Bird Management, U.S. Fish · and Wildlife Service, Washington D.C. September 1995. 15 pp. plus appendices.
I Verner, J. 1980. Bird communities of mixed-conifer fo rests of the Sierra Nevada. - Pp. 198-223 in R.M. DeGraff(tech coord.) Management of western forests and grasslands for nongame I birds. USDA For. Serv. Gen Tech. Rept. INT -86. 535 pp. - -,,...--�,,..- Verner, J. andA. S. Boss (tech coords.). 1980. Californiawildlif e and their habitats: westernSierra _._. · I Nevada. USDA For. Serv. Gen. Tech. Rept. PSW-37. Berkeley, CA. 439 pp. Warkentin, I.G. and D. Hernandez. 1996. The conservation implications of site-fidelity: a case study I involving nearctic-neotropical migrant songbirds wintering in a Costa Rica mangrove. Biol. Cons. 77:143-150.
I Wauer, R.H. Birds of Big Bend National Park and vicinity. Univ. of Texas Press, Austin. 223 pp ..
Weitzel, N.H. 1988. Nest-site competition between the European starling and native breeding birds I in northwesternNevada. Condor 90:515-517.
Wiens, J.A. 1975. Avian communities, energetics, and functions in coniferous fo rest habitats. Pp. I 226-265 in Smith, D.R. (tech. coord.) Symposium on the management of forest and range habitats fo rnongame birds. USDA For. Serv. Gen. Tech. Rept. W0-1, Wash. D.C. 343 pp.
I Willis, E.O., D.W. Snow, D.F. Stotz, and T.A. Parker III. 1993. Olive-sided flycatchers in southeasternBrazil. Wilson Bull. 105(1): 193-194.
- I Wm ker, K., D.W. Warner, andA.R. Weisbrod. 1992. Migration ofwoodlandbirds at a fragmented island stopover sight. Wilson Bull. 104(4):580-598. I Wright, J.M. 1997. in prep. Olive-sided flycatchers in central Alaska, 1994-1996. Alaska Dept. Fish andGame. Fed. Aid inWildl . Restor., Final Rep. Proj. SE-3-4. Juneau. I Zeiner, D.C., W. Laudenslayer Jr., K. Mayer, and M. White. 1990. California's wildlife. Vol. 2, Birds. Calif Dept. Fish andGame, Sacramento. 732 pp. I 58 I I I
Zink, R.M. and N.K. Johnson. 1984. Evolutionary genetics of flycatchers, 1. Sibling species in the genera Empidonax and Contopus. Syst. Zool. 33(2):205-216. I I I I I I - ..._: !..-�·"·�--- . I I I I I I I I I I 59 I I ------
Appendix A. Studies reporting olive-sided flycatcher density or abundance in western North America.
8 pairs/40 ha spot-mapping 3-7 year-old Douglas- northern California Hagar (1960) fir clearcuts
5-8 birds/40 ha spot-mapping coastal Douglas-fir southwestern British Horvath (1963) Columbia
3.7 pairs/40 ha spot-mapping single tree selection 1,400-1,980 m west-central Idaho · Medin and Booth (1989) logged Douglas-fir
5 birds/40 ha spot-mapping clearcut subalpine 3,050 in central Colorado Scott et al. (1982) fo rest
0.8 territories/40 spot-mapping aspen-pine 275-450 m northeastern Alberta Francis and Lumbis (1979) ha 4.4 territories/40 spot-mapping mature black spruce 275-450 m northeasternAlberta Francis and Lumbis (1979) ha muskeg 1.3-4.0 pairs/ spot-mapping giant sequoia fo rest 1,520-1,950 m northern Sierra Kilgore (1971) 40 ha Nevada Mountains
3 maleslkm2 spot-mapping early seral western 200-300 m northern Vancouver Buckner et al. (1975) hemlock (20 years) Island
5 pairs/40 ha spot-mapping Ponderosa pine, 3 and 2,090 m northern Arizona Overturf (1979) 4 years post-burn
3 birds/40 ha spot-mapping Ponderosa pine, 3 and 2,290-2,410 m near Flagstaff, Lowe et al. (1978) 7 years post-burn Arizona
12.8 birds/40 ha spot-mapping logged mixed conifer 2,682-2,805 m White Mts., Arizona Franzreb (1977)
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5.1 birds/ 40 ha spot-mapping unlogged mixed 2,682-2,805 m White Mts., Arizona Franzreb (1977) conifer
0. 9 pairs/40 ha spot-mapping mixed conifer, 6-8 2, 130 m central Sierra Bock and Lynch (1970) years post-burn Nevada Mts.
1 territory/ 40 ha spot-mapping mixed conifer, 6-8 2, 100 m eastern Sierra Raphael et al. (1987) years post-burn Nevada
3 territories/40 ha spot -mapping mixed conifer, 15-19 2, 100 m eastern Sierra Raphael et al. (1987) years post-burn Nevada
3.5 territories/40 spot-mapping mixed conifer, 21-25 2, 100 m eastern Sierra Raphael et al. (1987) ha years post-burn Nevada 1.7 pairs/40 ha spot -mapping spruce-fir, 2-3 years 2,360-2,550 m Yellowstone Pfister (I 980) post-burn National Park
0.6 and 5.6 spot-mapping lodgepole, 4-5 years 2,380 m Yellowstone Pfister (1980) pairs/40 ha post-burn National Park
4 birds/40 ha fixed radius early successional northern Idaho Peterson (1982) (25 m) point grand-fir/hemlock counts
0.08 and 0. 18 fixed radius heavy burn (>67% 1,830-1,980 m northeastern Oregon Sallabanks (1996) birds/count (50 m) point tree mortality) mixed counts conifer
0.02 and 0.08 fixed radius moderate burn (34- 1,830-1,980 m northeastern Oregon Sallabanks ( 1996) birds/count (50 m) point 66% tree mortality) counts mixed conifer
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0.03 and 0.05 fixed radius light bum (<34% tree 1,830-1,980 m northeastern Oregon Sallabanks (1996) birds/ count (50 m) point mortality) mixed counts conifer
0.17 birds/count fixed radius clearcut western 1,070-1,370 m northwestern Tobalske et al. (1991) (100 m) point larch/Douglas-fir Montana counts
0.07 birds/count fixed radius partial cut western 1,070-1,370 m northwestern Tobalske et al. (1991) (100 m) point larch/Douglas-fir Montana counts
0. 02 birds/count fixed radius unlogged western 1,070-1,370 m northwestern Tobalske et al. (1991) (100 m) point larch/Douglas-fir Montana counts
0. 11 birds/count point counts mixed conifer 1,200-1,450 m western Sierra Morrison et al. ( 1986) Nevada
0.47 birds/40 ha variable radius unmanaged old- 153-909 m southern Oregon Carey et al. (1991) point counts growth Douglas-fir Coast Range (200-525 years)
0.06 birds/40 ha variable radius unmanaged young 86-473 m southern Oregon Carey et al. (1991) point counts Douglas-fir ( 40-72 Coast Range years)
0. 03 birds/40 ha variable radius unmanaged mature 260-1,022 m southern Oregon Carey et al. (1991) point counts Douglas-fir (80-120 Coast Range years)
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2 birds/40 ha variable radius mixed aspen/conifer; 2,740 m west-central Scott and Crouch (1988) point counts 78 percent overstory Colorado
6 birds/40 ha variable radius mixed aspen/conifer; 2,740 m west -central Scott and Crouch (1988) point counts 64 percent overstory Colorado
3 birds/40 ha variable radius mixed aspen/conifer; 2,740 m west-central Scott and Crouch (1988) point counts 31 percent overstory Colorado
6 birds/40 ha variable radius mixed aspen/conifer; 1 2,740 m west-central Scott and Crouch (1988) point counts percent overstory Colorado
2.0-2.6 birds/40 variable radius pole-sapling subalpine 1,500-1,700 m Kootenay National Catt (1991) ha point counts fo rest Park, southeastern British Columbia
0.5 birds/40 ha variable radius mature subalpine 1,500-1,700 m Kootenay National Catt (1991) point counts fo rest Park, southeastern British Columbia
0.8-4.4 birds/40 variable radius old-growth subalpine 1,500-1,700 m Kootenay National Catt (1991) ha point counts fo rest Park, southeastern British Columbia
1.4 birds/40 ha variable radius sapling Douglas-fir (< < 1,500 m northwestern Raphael et al. (1988) point counts 20 years) California
0. 5 birds/40 ha variable radius sawtimber Douglas-fir < 1,500 m northwestern Raphael et al. (1988) point counts (20-100 years) California
1.2 birds/40 ha variable radius mature Douglas-fir (> < 1,500 m northwestern Raphael et al. (1988) point counts 100 years) California
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4.0 males/40 ha fixed width willow shrubin boreal <1,250 m Kluane Mts., Theberge (1976) transects (31 and subalpine fo rest southwest Yukon m)
3.0 males/ 40 ha fixed width spruce-poplar boreal <1,250 m Kluane Mts., Theberge ( 197 6) transects (31 and subalpine fo rest southwest Yukon m)
2.8 males/40 ha fixed width mature spruce boreal <1,250 m Kluane Mts., Theberge (1976) transects (3 1 and subalpine fo rest southwest Yukon m)
5 birds/40 ha fixed width open canopy mixed 1,830 m central Sierra Beedy (1981) transects ( 15 conifer Nevada Mts. m)
1 bird/40 ha fixed width clos�d canopy mixed 1,900 m central Sierra Beedy (1981) transects ( 15 conifer Nevada Mts. m)
7 birds/40 ha fixedwidth open canopy red fir 2, 145-2,225 m central Sierra Beedy (1981) transects ( 15 Nevada Mts. m)
2.4 birds/40 ha fixed width mature lodgepole pine, 2, 750-2,900 m southcentral Davis (1976) transects (25 1 0-year post-bum Wyoming m) 2.4 birds/40 ha fixed width clearcut subalpine 2,865-2,990 m southcentral Davis ( 197 6) transects (25 forest, 6-year post- Wyoming m) bum
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1.4 birds/40 ha fixed width spruce-fir 2,100-3,050 m northwestern Salt (1957) transects (30 Wyoming m)
2.5 pairs/40 ha transects mixed conifer 840 m northern Idaho Johnston (1949)
2 males/40 ha transects bog 150-A90 m Algonquin Park, Martin ( 1960) Ontario
' 14 males along 3- transects mixed conifer 1,220-1,520 m San Benito Mts., Johnson and Cicero (1985) mile transect SouthernCalif ornia
a Densities were converted if necessary to birds or pairs per 40 ha to facilitate comparison between studies.
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