Swainson's Thrush Research Articles

ESTIMATING ORIGINS OF THREE SPECIES OF NEOTROPICAL MIGRANT SONGBIRDS AT A GULF COAST STOPOVER SITE: COMBINING STABLE ISOTOPE AND GIS TOOLS

Abstract Measurement of stable-hydrogen isotopes (δD) in feathers of migrating birds can provide information on where feathers were grown in North America, at least to an approximate band of latitude. This approach has greatly increased our ability to investigate aspects of avian migration and stopover ecology, since origins of unmarked individuals at migration stopover sites can be estimated for the first time. However, few studies have explored the power of combining isotope measurements with geographic information system (GIS) methods. We measured δD values in feathers of hatching-year (HY) Swainson's Thrushes (Catharus ustulatus; n = 60), Wood Thrushes (Hylocichla mustelina; n = 113), and Gray Catbirds (Dumetella carolinensis; n = 158) at Ft. Morgan Peninsula, Alabama (30°10′N, 88°00′W), a migration stopover site along the Gulf coast. By applying an elevation-corrected hydrogen isotope basemap for birds in North America, we derived a GIS surface depicting expected feather δD values across the co...

SEX, WINGTIP SHAPE, AND WING-LOADING PREDICT ARRIVAL DATE AT A STOPOVER SITE IN THE SWAINSON'S THRUSH (CATHARUS USTULATUS)

Pointed wingtips and low wing-loading are believed to reduce the amount of energy used during migratory flight. If this is true, individuals with pointed wingtips or consistently low wing-loading should be able to migrate faster than conspecifics and may arrive on the breeding grounds and at stopover sites earlier. To test this hypothesis, I captured 97 Swainson's Thrushes (Catharus ustulatus; hereafter “thrushes”) during May in three consecutive field seasons, 2003-2005, at a stopover site in central Illinois. I used molecular techniques to sex 47 of these thrushes and created a discriminant function analysis using wing, tarsometatarsus, and tail lengths that predicted sex with 80.9% accuracy (P < 0.001). I applied this function to the remaining 50 thrushes so that I could control for any sexual dimorphism in morphology and arrival timing, and then examined seasonal trends in sex and morphology. Male thrushes arrived earlier at my stopover site than females (P < 0.001). After controlling for sex, thrushes with more pointed wingtips (P = 0.002) and lower wing-loading (P = 0.044) arrived earlier than thrushes with more rounded wingtips and higher wing-loading. The general linear model with sex, wingtip pointedness, and wing-loading explained nearly one-third of the variation in arrival date (P < 0.001, r2 = 0.281, n = 90). Pointed wingtips and lower wing-loading may help migratory birds cover distance more quickly and arrive at the breeding grounds sooner; alternatively, thrushes with more pointed wingtips and lower wing-loading may have departed from the wintering grounds earlier. If wing shape and size affect rate of migration, these variables may be important determinants of individual quality in migratory passerines. El Sexo, la Forma de las Puntas de las Alas y la Carga Alar Predicen la Fecha de Arribo de Catharus ustulatus a un Sitio de Escala Migratoria

Divergence in mating signals correlates with ecological variation in the migratory songbird, Swainson's thrush (Catharus ustulatus)

Song divergence among populations of passerine birds is recognized as a potentially important premating isolation mechanism and may represent the first step in speciation. Because song divergence may be influenced by an array of acoustic, ecological, and genetic factors, the study of its origin requires a multifaceted approach. Here we describe the relationship between acoustic, neutral genetic and ecological variation in five populations of the Swainson's thrush: two from coastal temperate rainforest habitat representing the 'russet-backed' subspecies group, two from inland coniferous forest habitat representing the 'olive-backed' subspecies group, and one mixed locality that resides within a contact zone between the two groups. Song in the five populations is analysed using a multivariate analysis of spectral and temporal measurements, population genetic structure is assessed using an analysis of five microsatellite loci and ecological differences between populations are quantified using an analysis of climatic parameters. Matrix correspondence tests are used to distinguish between the potential for drift and selection in driving song divergence. No significant correlation was found between acoustic and genetic distance suggesting that song divergence cannot be explained by drift alone. A significant correlation between ecological and acoustic distance after accounting for genetic distance, suggests a potential role for ecological selection on divergence in spectral and temporal components of Swainson's thrush song.

Daytime naps in night-migrating birds: behavioural adaptation to seasonal sleep deprivation in the Swainson's thrush, Catharus ustulatus

Many typically diurnal songbird species are routinely subjected to severe sleep deprivation during their seasonal, nocturnal migrations, yet they seem to suffer few of the negative consequences so obvious in sleep-deprived mammals. Studying the Swainson's thrush, a Nearctic–Neotropical long-distance migrant, we investigated seasonal changes in behaviour as possible adaptations to naturally occurring sleep loss during the migratory season. We found that captive Swainson's thrushes substantially change their daytime behaviour in response to significant loss of night-time sleep during migration, engaging in numerous episodes of daytime sleep, unilateral eye closure and drowsiness. Our observations suggest that brief episodes of sleep and sleep-like behaviour during the day, including lateralized naps in the form of unihemispheric sleep, enable migratory birds to compensate for extended periods of nocturnal sleep loss. Although episodes of daytime sleep and unilateral eye closure rarely exceed 30 s, these brief episodes, considering the short sleep cycle of birds, appear sufficiently long to provide recuperative opportunities without stretching a migrant's time budget. Importantly, the temporal structure of the daytime rest and sleep behaviour would not preclude migrants from foraging and replenishing fat deposits during a large portion of the day.

Climate change and the origin of migratory pathways in the Swainson's thrush,Catharus ustulatus

AbstractAim To provide a spatially explicit model of how geographic distributions at the last glacial maximum (LGM) and post‐glacial colonization routes shaped current migratory pathways in the Swainson's thrush,Catharus ustulatus, a long‐distance migratory bird.Location The Swainson's thrush breeds in boreal forest regions of the United States and Canada as well as in riparian woodlands along the Pacific coast of North America.Methods Palaeodistribution modelling is combined with mtDNA phylogeography to predict the breeding range of the Swainson's thrush at the LGM. Quantitative environmental analysis and bioclimatic modelling are used to reconstruct the most likely post‐glacial colonization pathways. A maximum likelihood method for estimating growth rates is used to approximate the relative change in population size since the LGM.Main conclusions The palaeodistribution models are concordant with the Swainson's thrush mtDNA phylogeography, suggesting that the inland and coastal groups were geographically isolated in eastern (inland) and western (coastal) regions at the LGM. Estimates of change in population size based on genetic data are remarkably consistent with estimates of change in range size, suggesting that the coastal group has undergone a 2‐ to 3‐fold demographic and range expansion, while the inland group has undergone a 6‐ to 12‐fold demographic and range expansion since the LGM. Bioclimatic analyses strongly support the hypothesis that populations expanding out of the east into previously glaciated areas in the west were undergoing a natural extension of their range by tracking the changes in climatic conditions. The combination of bioclimatic and molecular analyses is consistent with the idea that coastal and inland groups expanded from separate eastern and western regions after the LGM and that the current migratory pathway of the inland group retraces its post‐glacial colonization route.

Modeling Movement of West Nile Virus in the Western Hemisphere

We modeled West Nile virus (WNV) movement rates and patterns based on a migratory bird agent (the Swainson's Thrush) and a resident bird agent (the House Sparrow), and compared the results of these models with actual movement data to investigate the likelihood that the pattern of WNV outbreaks observed in the New World was consistent with migrant bird-mediated spread, as reported from the Old World. We found that, contrary to Old World patterns, WNV activity in the Western Hemisphere does not seem consistent with movement by infected migrant birds. Instead WNV spread appears best explained by a non-directional movement, perhaps that of dispersing resident birds.

Seasonal Differences in Immunological Condition of Three Species of Thrushes

Abstract Migratory birds are exposed to a diverse pathogen fauna by virtue of their long-distance travels. Although the immune system is an organism's primary defense against pathogenic microorganisms, few studies have investigated avian immune function during migration, much less shown seasonal differences in immune function. We describe the immunological condition of three intercontinental migratory species, Swainson's Thrush (Catharus ustulatus), Veery (C. fuscescens), and Wood Thrush (Hylocichla mustelina) during spring migration. In addition, we compare their immunological condition with conspecifics captured during fall migration and during the breeding season to provide a frame of reference for the spring immunological data. Measures of immunological condition presented include total leukocyte count, heterophil:lymphocyte (H:L) ratio, heterophil and lymphocyte counts, hematocrit, and IgG titers. In addition, we assessed each bird's energetic condition by measuring body mass and calculating a size-corrected condition index. Migrating birds had lower leukocyte and lymphocyte counts, lower hematocrit, reduced fat stores, and higher H:L ratios relative to nonmigrating individuals sampled during the breeding season. We also found that birds sampled during spring migration had lower lymphocyte counts and reduced fat stores, and higher heterophil counts and H:L ratios than fall migrants. Our results suggest that migrating birds are immunocompromised compared with conspecifics during the breeding season. Furthermore, compared with conspecifics sampled after a shorter overland flight, migrants sampled after crossing the Gulf of Mexico exhibited higher H:L ratios, which is indicative of heightened energetic stress.

INSULAR AND MIGRANT SPECIES, LONGEVITY RECORDS, AND NEW SPECIES RECORDS ON GUANA ISLAND, BRITISH VIRGIN ISLANDS

Abstract We conducted mist netting each October from 1994 to 2004 on Guana Island, British Virgin Islands, and recorded bird sightings to develop a more complete inventory of the island's resident and migrant species. During our study, we recorded four new species for the British Virgin Islands: Magnolia Warbler (Dendroica magnolia; 1996), Golden-winged Warbler (Vermivora chrysoptera; 1997), Swainson's Thrush (Catharus ustulatus; 2000), and Red-necked Phalarope (Phalaropus lobatus; 2004). Blackpoll Warbler (Dendroica striata) was the most frequently captured Neotropical migrant landbird, despite only being first detected in the region in 1989. Captures and detections of other Neotropical migrant landbirds suggest that many species may be more common in the region than previously believed, or, as speculated by other researchers, that migrant routes may be shifting eastward due to habitat degradation on western Caribbean islands. We also used recapture data to establish longevity records of resident species...

SEASONAL DIFFERENCES IN IMMUNOLOGICAL CONDITION OF THREE SPECIES OF THRUSHES

Abstract Migratory birds are exposed to a diverse pathogen fauna by virtue of their long-distance travels. Although the immune system is an organism's primary defense against pathogenic microorganisms, few studies have investigated avian immune function during migration, much less shown seasonal differences in immune function. We describe the immunological condition of three intercontinental migratory species, Swainson's Thrush (Catharus ustulatus), Veery (C. fuscescens), and Wood Thrush (Hylocichla mustelina) during spring migration. In addition, we compare their immunological condition with conspecifics captured during fall migration and during the breeding season to provide a frame of reference for the spring immunological data. Measures of immunological condition presented include total leukocyte count, heterophil:lymphocyte (H:L) ratio, heterophil and lymphocyte counts, hematocrit, and IgG titers. In addition, we assessed each bird's energetic condition by measuring body mass and calculating a size-c...

SEASONAL VARIATION OF INFESTATION BY ECTOPARASITIC CHIGGER MITE LARVAE (ACARINA: TROMBICULIDAE) ON RESIDENT AND MIGRATORY BIRDS IN COFFEE AGROECOSYSTEMS OF CHIAPAS, MEXICO

Parasitism is not well documented for birds found in tropical habitats. Long-distance migratory birds may face additional risks to an already hazardous journey when infected. This study explores the ecology of an ectoparasite infestation in Chiapas, Mexico. During a mist-netting project in 2 different coffee management systems, chigger mites (Acarina: Trombiculidae), ectoparasitic during the larval stage, were found on both resident and migratory birds. Using a rapid assessment protocol, it was observed that 17 of 26 species of long-distance migrants and 33 of 71 resident species had at least 1 infested individual. Infestation prevalences were unexpectedly high on some long-distance migrants, as high as 0.73 for Swainson's thrush (Catharus ustulatus), a value on par with heavily infested resident species. Prevalence was highest during winter sampling: 0.18 overall, 0.16 of migrants, and 0.23 of residents. Prevalence was 0.14 for resident birds during the summer breeding season. Mean abundance and mean intensity of infestation are reported for 97 species captured and inspected during the course of this study. In this region, chigger mite larvae are relatively common on birds and their abundance varies seasonally. High prevalence for some migratory birds suggests that more research and monitoring of ectoparasites are needed, especially in light of emerging diseases.

COMBINING ISOTOPIC AND GENETIC MARKERS TO IDENTIFY BREEDING ORIGINS OF MIGRANT BIRDS

A quantitative method for linking reproductive and nonreproductive phases of migratory life cycles is fundamental to understanding the biology of migratory organisms. Here we combine genetic (mtDNA) and biochemical (stable isotope) information to examine seasonal movements in the Swainson's Thrush (Catharus ustulatus), a Neotropical migrant. We show that when these intrinsic markers are used in concert, they can predict the site-specific origin of thrushes with 76–80% accuracy. Genetic and isotope data needed for these classifications can be obtained from migratory organisms at any phase of the life cycle. We demonstrate how this classification analysis can be used to infer breeding origins of samples gathered during the nonreproductive phases of the life cycle. Based on these results, we argue that further integration of methodologies will refine the scale at which linkages between reproductive and nonreproductive phases of the life cycle can be quantified.

HABITAT USE BY RIPARIAN AND UPLAND BIRDS IN OLD-GROWTH COASTAL BRITISH COLUMBIA RAINFOREST

The value of riparian habitats to birds differs among ecosystems. I tested whether riparian habitat near large streams and rivers in the Pacific Northwest supported a higher abundance and diversity of birds than adjacent upland forest. From 1996 to 1998, I surveyed breeding birds at four 9-ha sites in coastal western hemlock forest on western Vancouver Island, British Columbia. Five species of forest generalists dominated both riparian and upland bird communities: Winter Wren (Troglodytes troglodytes), Chestnut-backed Chickadee (Poecile rufescens), American Robin (Turdus migratorius), Swainson's Thrush (Catharus ustulatus), and Pacific-slope Flycatcher (Empidonax difficilis). Species richness and total abundance were similar over the riparian-to-upland gradient, whereas abundances of riparian specialists and aerial foragers declined with distance from the river. To explore whether vegetation composition and structure explained bird distribution patterns, I sampled three locations along both riparian and upland transects at each site. Riparian areas had higher densities of deciduous trees; conifer and snag densities were higher in upland areas. Salmonberry (Rubus spectabilis) cover was marginally higher in riparian areas and blueberry (Vaccinium spp.) cover was higher in upland areas. There was little effect of distance from the river on most bird species, but there were stronger associations of birds with specific vegetation attributes. Tree and snag densities explained the most variation in abundance of aerial foragers, and eight of nine individual species, whereas distance from the river and shrub cover were important predictors of Hammond's Flycatcher (Empidonax hammondii) abundance. Apart from riparian specialists and a few species with strong vegetation associations, bird assemblages in riparian and upland habitats of this moist forest type were dominated by similar sets of generalist species.

Nocturnal activity and energetic condition of spring landbird migrants at Braddock Bay, Lake Ontario

Abstract We investigated the relationship between migratory restlessness and stored energy reserves in two species of landbird migrants at Braddock Bay, Lake Ontario during spring 1999 and spring 2000. There was no significant difference in the amount of nighttime locomotor activity between lean and fat Swainson's Thrushes (Catharus ustulatus) or White-throated Sparrows (Zonotrichia albicollis) held overnight in activity cages. We found no significant relationships between nocturnal activity level and energetic condition (mass/wing chord) or date of capture. In addition, there were no significant differences in nocturnal activity levels between age groups in Swainson's Thrushes. These results suggest that the migratory restlessness of spring migrants stopping at this site is not strongly influenced by their energetic condition upon arrival, regardless of age or date of passage. Birds nearing the end of their spring migratory route that are very close to their breeding grounds may show decreased levels of ...

Resource Selection by Juvenile Swainson's Thrushes During the Postfledging Period

Abstract Resource-selection studies of passerine birds during the breeding season have mainly been limited to understanding those factors important to nesting. However, little is known about what resources are selected by juveniles that are no longer dependent on their parents. The postfledging period may be a critical part of the breeding season for independent juveniles because they must avoid predators and learn to forage on a changing resource base. We used radio-telemetry to study postfledging habitat use and resource selection of juvenile Swainson's Thrushes (Catharus ustulatus) in coastal California from 2000 to 2002. We generated population-level contours (50% and 95% fixed-kernel) to describe habitat use by independent juveniles, and we determined juvenile resource selection by comparing vegetation characteristics at sites used by juveniles versus random sites. Juvenile Swainson's Thrushes used mixed-hardwood forest and coastal scrub during the postfledging period as well as riparian vegetation used by nesting adults. The most parsimonious predictors of resource selection were fruit abundance variables, suggesting that postfledging habitat selection by the Swainson's Thrush is best explained by the optimal-foraging hypothesis. We suggest that juvenile thrushes can track food resources in a habitat mosaic and use vegetation types distinct from what is traditionally considered Swainson's Thrush breeding habitat. Selección de Recursos por Juveniles de Cathatus ustulatus Durante el Periodo de Emancipación Resumen. Los estudios de selección de recursos en aves paserinas durante la estación reproductiva, se han centrado principalmente en entender los factores importantes para la anidación. Sin embargo, se sabe poco acerca de los recursos seleccionados por los juveniles que ya no dependen de sus padres. Para los juveniles independientes, el periodo de emancipación podría ser una parte crítica de la estación reproductiva en la que deben evitar depredadores y aprender a forrajear sobre una base de recursos fluctuante. Por medio de telemetría, estudiamos el uso de hábitat y selección de recursos en juveniles del zorzal Catharus ustulatus en la costa de California entre los años 2000 y 2002. A nivel de población, generamos polígonos (de 50% y 95% de “kernel” fijo) para describir la utilización de hábitat por juveniles independientes, y para determinar la selección de recursos comparamos las características de la vegetación de los sitios utilizados con la de sitios aleatorios pareados. Los juveniles utilizaron bosques mixtos y matorral costero durante el periodo de emancipación, así como la vegetación riparia utilizada por adultos nidificantes. Las variables con las predicciones más parsimoniosas del uso de recursos fueron las relacionadas con la abundancia de frutos, lo que sugiere que la selección de hábitat de emancipación por C. ustulatus es explicada en mejores términos por la hipótesis de forrajeo óptimo. Sugerimos que los zorzales juveniles pueden encontrar recursos alimenticios en mosaicos de hábitat y usar tipos de vegetación distintos a los que tradicionalmente se consideran como hábitat de anidación.

Biotelemetry of New World thrushes during migration: Physiology, energetics and orientation in the wild

Billions of songbirds migrate between continents each year, but we have yet to obtain enough information on in-flight physiology and energetics to fully understand the migratory behavior of any one species. New World Catharus thrushes are common nocturnal migrants amenable to biotelemetry, allowing us to measure physiological parameters during migratory flight in the wild. Here, we review work by the authors on Catharus thrush in-flight physiology during spring migration in continental North America and present new data on individual variation in energy use during migratory flight. Previous work demonstrated that (1) a number of simple behavioral rules are sufficient to explain the initiation of individual migratory flights made by Catharus thrushes, (2) the thrushes used a magnetic compass to orient during the night rather than celestial cues and that they calibrated this magnetic compass each day using cues associated with the setting sun, (3) in total, Catharus thrushes used approximately twice as much energy during stopovers than they used during migratory flight, and (4) thrushes may use more energy when thermoregulating on cold days than on days when they make short migratory flights. Recently, we built upon this work and used newly-developed transmitters to measure heart rate, wingbeat frequency and respiration rate of free-flying Swainson's Thrushes (C. ustulatus). We found a large amount of between-individual variation in average heart rate after ascent (range 12.06-14.81 Hz, mean ± SD, 13.48 ± 0.75, n = 10), average wingbeat frequency after ascent (10.25-11.75 Hz, 10.82 ± 0.49, n = 10), and the difference between the two variables (1.5-3.84 Hz, 2.53 ± 0.76, n = 8). Both heart rate and wingbeat frequency were significantly higher during ascent than later in the flight. We propose biotelemetry as a means to understand energetic trade-offs and decisions during natural migratory flight in songbirds. To further our knowledge of intercontinental songbird migration and the connectivity between wintering and breeding sites, we outline plans for a satellite-based global tracking system for <1 g transmitters.

RESOURCE SELECTION BY JUVENILE SWAINSON'S THRUSHES DURING THE POSTFLEDGING PERIOD

Abstract Resource-selection studies of passerine birds during the breeding season have mainly been limited to understanding those factors important to nesting. However, little is known about what resources are selected by juveniles that are no longer dependent on their parents. The postfledging period may be a critical part of the breeding season for independent juveniles because they must avoid predators and learn to forage on a changing resource base. We used radio-telemetry to study postfledging habitat use and resource selection of juvenile Swainson's Thrushes (Catharus ustulatus) in coastal California from 2000 to 2002. We generated population-level contours (50% and 95% fixed-kernel) to describe habitat use by independent juveniles, and we determined juvenile resource selection by comparing vegetation characteristics at sites used by juveniles versus random sites. Juvenile Swainson's Thrushes used mixed-hardwood forest and coastal scrub during the postfledging period as well as riparian vegetation u...

LANDBIRD USE OF RIPARIAN AND UPLAND FOREST STOPOVER HABITATS IN AN URBAN LANDSCAPE

Abstract Stopover habitat relationships of landbirds are not well known and this constitutes a shortcoming in conservation plans for migratory birds. We compared migrant use of mature upland and riparian forests during spring in an urbanizing landscape within central Ohio. We surveyed stopover migrants along 250-m transects, and quantified both local- and landscape-level habitat characteristics (percent urban and forest land). During spring stopover, migrant abundance was 86% and 118% higher in upland forests for Nearctic-Neotropical transient (long-distance migrants) and temperate transients (short-distance migrants), respectively. Of 27 transient species, 22 species differed in their use of riparian and upland forests, and 20 of those were most abundant in upland forest (e.g., Blue-headed Vireo [Vireo solitarius], Least Flycatcher [Empidonax minimus], Swainson's Thrush [Catharus ustulatus], Nashville Warbler [Vermivora ruficapilla], Magnolia Warbler [Dendroica magnolia], Bay-breasted Warbler [D. castane...

BREEDING BIRDS OF RESEARCH NATURAL AREAS IN SOUTHEASTERN ALASKA

Abstract The Tongass National Forest encompasses a large expanse of temperate rainforest in southeastern Alaska and contains 12 designated Research Natural Areas (RNAs). Existing in as near a natural condition as possible, RNAs receive minimal commercial and recreational use. Because few bird studies have been conducted on RNAs, we used point counts and area searches to determine the occurrence and abundance of breeding landbirds present in vegetation communities of RNAs. Of 49 species of small landbirds detected during area searches, the most widely distributed birds among RNAs were rufous hummingbird (Selasphorus rufa), chestnut-backed chickadee (Poecile rufescens), winter wren (Troglodytes troglodytes), golden-crowned kinglet (Regulus satrapa), Swainson's thrush (Catharus ustulatus), hermit thrush (C. guttatus), varied thrush (Ixoreus naevius), and Townsend's warbler (Dendroica townsendi). The 8 most abundant species recorded on 187 point counts (>0.5 birds/point) were Pacific-slope flycatcher (Empidon...

Juvenile and Adult Survival of Swainson's Thrush (Catharus Ustulatus) in Coastal California: Annual Estimates Using Capture-Recapture Analyses

Abstract We estimated annual rates of survival for juvenile and adult Swainson's Thrushes (Catharus ustulatus) using capture-recapture analyses from 22 years of mist-neting data in coastal California (n= 2,651 individual captures). Our apparent survival estimate was 56% for adults and 25% for juveniles. We are the first to estimate an annual juvenile survival rate for a Neotropical migrant using capture-recapture probability estimates. Like most estimates of annual survival, we could not distinguish between dispersal away from our study area (which is likely high for juveniles) and mortality. Hence, survival is underestimated. However, our juvenile survival estimate did not include the period from fledging to independence, a time when mortality can be high. Many researchers have assumed juvenile survival to be half that of adult survival in population models (e.g. source-sink). Our juvenile to adult survival ratio was 45% (95% CI = 27 to 65%). We caution researchers from simply assuming that juvenile survival approximates half of adult survival when modeling populations and suggest using a range of values. Using a range of values is prudent because of the potential for annual variation, site-specific variation, and especially because estimates are imprecise or completely lacking.

BOREAL FOREST SONGBIRD COMMUNITIES OF THE LIARD VALLEY, NORTHWEST TERRITORIES, CANADA

Abstract Songbird communities in the boreal forest of the Liard Valley, Northwest Territories, Canada, are described after three years of study. Point count stations (n = 195) were placed in six types of forest (mature deciduous, coniferous, and mixedwood; young forests; wooded bogs; clearcuts) in a 700-km2 area. Vegetation characteristics at each station were also measured. Eighty-five species of birds (59 passerine species) occurred in 11 647 detections. Mixedwood forests had the highest richness of songbirds (∼41 species per 800 individuals) of the six forest types, and contained approximately 30% more individuals than nearly pure coniferous or deciduous forests. Species richness and relative abundance was 10–50% lower than in comparable forests farther south and east, and the difference was most pronounced in deciduous forests. Communities were dominated by a few species, especially Tennessee Warbler (Vermivora peregrina), Magnolia Warbler (Dendroica magnolia), Swainson's Thrush (Catharus ustulatus), ...