Neotropical Migrants Research Articles

Physiological assessment of the effects of changing water levels associated with reservoir management on fattening rates of neotropical migrants at a stopover site.

Riparian habitat makes up a small fraction of the landscape but provides important stopover habitat for migratory birds. Hydroelectric dam operations cause fluctuations in water levels that can change the amount or quality of riparian habitat, which in turn might affect potential fattening rates of migrant birds. Here we used plasma metabolite analysis to estimate variation in fattening rate in relationship to variable water levels associated with reservoir management in four species of neotropical migratory songbirds using riparian habitat at a dam-impacted stopover site in Revelstoke, British Columbia, Canada. Residual plasma triglyceride, our measure of estimated fattening rate, varied systematically with time of day and Julian date and varied consistently among species, but did not vary with age or sex. Controlling for potentially confounding variables, we found no inter-annual variation in estimated fattening rate, even though there were marked differences in water levels among years. Likewise, there was no relationship between daily variation in water levels and estimated fattening rate. Data on feather isotopes (δD), indicative of migratory origin, did not add explanatory power to our models. There was inter-annual variation in plasma glycerol and β-hydroxybutyrate levels and significant, though weak, relationships between these metabolites and water level (higher metabolite levels when drier) that might indicate effects on 'body condition' independent of fattening rate. Our study suggests that, at present, although hydroelectric dam operations influence water levels in the Arrows Lake Reservoir and adjacent riparian habitats, this does not significantly impact fattening rates of migratory passerines using these habitats.

Wind speed during migration influences the survival, timing of breeding, and productivity of a neotropical migrant, Setophaga petechia.

Over the course of the annual cycle, migratory bird populations can be impacted by environmental conditions in regions separated by thousands of kilometers. We examine how climatic conditions during discrete periods of the annual cycle influence the demography of a nearctic-neotropical migrant population of yellow warblers (Setophaga petechia), that breed in western Canada and overwinter in Mexico. We demonstrate that wind conditions during spring migration are the best predictor of apparent annual adult survival, male arrival date, female clutch initiation date and, via these timing effects, annual productivity. We find little evidence that conditions during the wintering period influence breeding phenology and apparent annual survival. Our study emphasizes the importance of climatic conditions experienced by migrants during the migratory period and indicates that geography may play a role in which period most strongly impacts migrant populations.

Landscape and regional context differentially affect nest parasitism and nest predation for Wood Thrush in central Virginia, USA

ABSTRACT Many empirical studies have shown that forest-breeding songbirds, and Neotropical migrants in particular, suffer greater rates of nest predation and nest parasitism in smaller forest patches and in fragmented landscapes. To compare the performance of different metrics of spatial habitat configuration resulting from deforestation, we studied nest predation and nest parasitism rates at 200 Wood Thrush (Hylocichla mustelina) nests in eight forest fragments ranging from 82 to 9,171 ha in central Virginia, USA. We analyzed nest parasitism rates using logistic regression and we analyzed daily nest predation rates under a multistate competing risks design. For both analyses we compared the performance of 16 covariates, 11 of which related to the spatial configuration of habitat (e.g., patch size, distance to edge, percent core forest in proximity to nest) and 5 of which were unrelated to habitat (e.g., year, serial date, nest height). Distance to agriculture gained the greatest support in analyses of ne...

Characterization of muscle plasticity in a neotropical migrant, Dumetella carolinesis (gray catbird) (878.2)

This study focuses on how avian migration is facilitated by changes in organismal metabolism, muscle structure, and muscle metabolism. These specific migratory changes were examined across the annual cycle on‐an organismal level by investigating whole body oxidative capacity (ability to use energy) and, on a tissue level by characterizing muscle tissue size and oxidative capacity. In order to quantify whole body oxidative capacity, summit metabolism was measured to determine the peak oxygen consumed by each individual. Birds were euthanized and the pectoralis (flight muscle) and gastrocnemius (leg muscle) were removed and weighed. Mitochondrial content of the muscle was quantified by measuring enzyme activity via citrate synthase and cytochrome oxidase assays to determine oxidative capacity of the muscles. Summit metabolism and flight muscle mass were greatest during southward migration compared to temperate breeding and tropical wintering. The Gray Catbird displays phenotypic plasticity during migration compared to non‐migratory periods suggesting that augmentation of the flight muscle and increased metabolism are necessary for migration.Grant Funding Source: Supported by NSF #IOS‐1257455 to PJS

Individual variation in migratory path and behavior among Eastern Lark Sparrows

AbstractTwo general migration strategies prevail among temperate-breeding migratory songbirds of North America. Most “Eastern” birds migrate relatively directly from breeding to wintering grounds immediately after molting, whereas a substantial proportion of “Western” species depart breeding grounds early, and molt during extended migratory stopovers before reaching wintering areas. The Lark Sparrow is one of a few Western Neotropical migrants with a breeding range that extends into regions dominated by Eastern species. We sought to determine whether Eastern Lark Sparrows migrated in a manner consistent with Western conspecifics or follow typical Eastern songbird migratory patterns. To do so, we tracked individual Eastern Lark Sparrows equipped with geolocators between their breeding grounds in Ohio and their unknown wintering locations. Data from three Ohio Lark Sparrows revealed 1) individual variation in the duration and directness of autumn migrations, 2) autumn departures that consistently preceded molt, 3) wintering grounds in the central highlands of Mexico, and 4) brief and direct spring migrations. These observations suggest that eastern populations of prevailingly Western migrants, such as Lark Sparrows, may be behaviorally constrained to depart breeding grounds before molt, but may facultatively adjust migration en route.

Within-season nesting dispersal and molt dispersal are linked to habitat shifts in a Neotropical migratory songbird

Dispersal decisions of songbirds are relatively well understood between breeding seasons, but far less is known about dispersal between nesting attempts and during the molting period. There are several non-mutually exclusive hypotheses for why birds disperse during breeding and molt including: (1) avoiding predation, (2) because of depleted resources, or (3) seeking higher quality habitat. In this study, we evaluated the above hypotheses by radio-tracking a Neotropical migrant, the Wood Thrush (Hylocichla mustelina), during breeding and molt. During breeding, 30% (7/23) of females moved territories within-season. Females were not more likely to move off-territory following nest predation, and dispersing females were not in poorer nutritional state than non-dispersing females prior to the move. However, females occupying nest sites with large trees, high canopy height and percent canopy cover, and low percent ground cover were more likely to move off-territory for their second nest to sites with few large trees, a low canopy height and cover, and high percent ground cover. During the molting period, 61% (28/46) of birds moved off-territory to molt. Molting areas were associated with more shrubs and fruiting trees compared with breeding territories. There were no sex or age effects as to whether a bird molted on or off their breeding territory. We suggest that off-territory movements during the nesting period are to seek more suitable nesting vegetation, rather than specifically avoiding predation or because of reduced resource availability. This study has additionally shown that, without radio-telemetry, detecting off-territory movements during breeding is difficult and neglecting to include these movements may result in an underestimation of annual productivity.

The effect of white-tailed deer density on breeding songbirds in Delaware

Most population goals for white-tailed deer (Odocoileus virginianus) are based solely on deer data, with little consideration for other parts of the ecosystem. A wider ecological approach is needed for more justifiable target deer densities. We investigated the use of birds as coarse-scale indicators to determine an ecological carrying capacity for deer management by studying the relationship between the forest bird community and deer density in Delaware, USA. Using Breeding Bird Survey data from 2005 to 2009, targeted point-count data from 2008 to 2009 and Division of Fish and Wildlife deer-density data from the same time periods, we compared avian species richness and relative abundance with deer density. We divided deer densities into low (≤10 deer/km2), moderate (11–19 deer/km2), and high (≥20 deer/km2) categories. We placed birds into 6 deer-sensitive guilds: interior forest obligates, ground nesters, shrub nesters, ground gleaners, low-canopy foragers, and Neotropical migrants, as well as 1 “guild” that consisted of species found to be sensitive to deer density in past literature. The abundance or richness of most guilds and species did not differ by deer density. However, there were 1.08 more shrub nesters and 0.55 more species of shrub nesting birds in low-deer-density areas than in high-deer-density areas. Areas of moderate and low deer densities had ≥0.35 more species of low-canopy foragers than did areas of high deer densities. Low-deer-density areas had ≥0.59 more individual Neotropical migrants compared with moderate- or high-deer-density areas. Similarly, areas of low deer densities had ≥0.49 more migrant species than did areas of higher densities. Low-deer-density areas had ≥0.17 more ovenbirds compared with high- and moderate-deer-density areas. Great crested flycatchers (Myiarchus crinitus) had 3 times greater odds of being found in low-deer-density areas than in high-deer-density areas. Chipping sparrows (Spizella passerina), Acadian flycatchers (Empidonax virescens), and red-eyed vireos (Vireo olivaceus) all had 2 times greater odds of being found in low-deer-density areas than high-deer-density areas. Our results suggest that areas in Delaware with densities of <20 deer/km2 have the greatest avian richness and abundance. These findings are the first step toward determining an ecological carrying capacity for white-tailed deer. © 2013 The Wildlife Society.

Distribución geográfica de la avifauna en la Sierra Madre Oriental de San Luis Potosí, México: un análisis regional de su estado de conservación

The Sierra Madre Oriental region in the mexican state of San Luis Potosi is a relevant place for bird conservation at a country level. Therefore the main goal of this study was to analyze the geographic patterns of distribution and the conservation current state of the birds, to support the needs to expand the conservation areas in the future. Data was collected from various databases of zoological museums and collections, and field sampling methods conducted from January 2009 to May 2011. Potential distributions were modeled for 284 species using GARP software and then a map was developed to determine areas with favorable environmental characteristics for the distribution of species richness. Finally, the importance of conservation areas for the potential distribution of birds in the region was evaluated. A total of 359 species were recorded of which 71.4% are permanent residents, 19% are winter migrants and 4% are summer residents. From this total, 41 species were endemic, 47 were species at risk and 149 were neotropical migrants. The largest species richness correspond to oak forests, cloud forests, and tropical moist forests located at altitudes from 100m to 1 500m. Their potential distribution was concentrated towards the center and Southeast of the study area. Only 10% of areas with a high potential conservation was included in areas of priority for bird conservation (AICA) and just 3% of all potential areas were under some governmental category of protection. However, no conservation area has a management plan currently applied and monitored. The information generated is important for the development of management proposals for birds conservation in the region.

Environmental conditions on wintering grounds and during migration influence spring nutritional condition and arrival phenology of Neotropical migrants at a northern stopover site

Assessing effects of winter habitat quality and environmental conditions on fitness of migratory birds is important to understand factors that regulate migratory bird populations throughout the annual cycle. We evaluated effects of winter habitat occupancy, as inferred from tissue stable-carbon (δ13C) and -nitrogen (δ15N) isotope values, on nutritional condition and arrival date of seven long-distance Nearctic–Neotropical migratory species sampled at Delta Marsh Bird Observatory (DMBO, Manitoba, Canada) during their spring migration to more northerly breeding areas. Additionally, we used a long-term dataset of DMBO to assess the effect of May minimum temperature, May minimum daily temperature, and El Nino–Southern Oscillation (ENSO) index on body condition and spring arrival date. A positive effect of assumed mesic winter habitat on nutritional condition and arrival phenology was detected primarily in species overwintering in the Caribbean (Palm Warbler Setophaga palmarum, Northern Waterthrush Parkesianovaboracensis). We caution, then, against generalizing the results of previous isotopic studies inferring winter habitat use applied to Neotropical migrants wintering in the Caribbean (e.g., American Redstart Setophaga ruticilla) to those species or populations wintering elsewhere and especially away from dichotomous mangrove versus scrub habitats. In general, birds arrived later and in lower nutritional condition during colder springs, and early migrants did not adjust their timing of migration to spring temperature. Early arrival was associated with poorer nutritional condition, and most species had their lowest nutritional condition during the coldest periods of migration. ENSO, probably through its influence on weather and food availability during winter, carried over to northern latitudes and affected both spring arrival date and nutritional condition.

Effects of Exurban Development and Temperature on Bird Species in the Southern Appalachians

Land-use dynamics and climatic gradients have large effects on many terrestrial systems. Exurban development, one of the fastest growing forms of land use in the United States, may affect wildlife through habitat fragmentation and building presence may alter habitat quality. We studied the effects of residential development and temperature gradients on bird species occurrence at 140 study sites in the southern Appalachian Mountains (North Carolina, U.S.A.) that varied with respect to building density and elevation. We used occupancy models to determine 36 bird species' associations with building density, forest canopy cover, average daily mean temperature, and an interaction between building density and mean temperature. Responses varied with habitat requirement, breeding range, and migration distance. Building density and mean temperature were both included in the top occupancy models for 19 of 36 species and a building density by temperature interaction was included in models for 8 bird species. As exurban development expands in the southern Appalachians, interior forest species and Neotropical migrants are likely to decline, but shrubland or edge species are not likely to benefit. Overall, effects of building density were greater than those of forest canopy cover. Exurban development had a greater effect on birds at high elevations due to a greater abundance of sensitive forest-interior species and Neotropical migrants. A warming climate may exacerbate these negative effects.

Association of Scissor-Tailed Flycatchers (Tyrannus forficatus) With Specific Land-Cover Types In South-Central Texas

Scissor-tailed Flycatchers (Tyrannus forficatus) are insectivorous Neotropical migrants that breed in the south-central United States. We examined their fine-scale (circles 300 m in radius centered on observed flycatcher locations) associations with different land cover types in south-central Texas. Scissor-tailed Flycatchers use a sit-and-scan foraging strategy; therefore, we expected the species would be positively associated with open land cover types (vegetation with little or no canopy) such as grassland, pasture/hayfield and cropland, and negatively associated with forest and shrubland given that the latter could obstruct visual scanning. We conducted 44 surveys from 9 May 2011 to 15 December 2011 by slowly driving (30 km/h) rural roads throughout 15 counties in south-central Texas and 3 near the coast of the Gulf of Mexico. Using ArcGIS, we quantified the percent cover of four general land cover types (urban/developed land, forest/shrub, grassland/pasture/hay, and cropland) within 300 m of each flycatcher location. Statistical analysis involved comparing the land cover of the flycatcher locations to a set of random points along the same routes. On average, flycatcher locations had significantly more grassland/pasture/hay than did random points (38.8 vs. 31.2%) and significantly less forest/shrub (29.9 vs. 36.7%). Therefore, although flycatchers may associate with open land cover at a rate greater than its overall availability, they generally occupy locations that have a mix of open and closed land cover. Knowledge of flycatcher habitat use at a fine-scale could be useful to the successful conservation of this species.

Occurrence of the Connecticut Warbler Increases with Size of Patches of Coniferous Forest

Abstract. The Connecticut Warbler (Oporornis agilis) is a rare and declining neotropical migrant that breeds in the north-central United States and south-central Canada. To better understand the species' habitat needs, we analyzed 371 observations of the Connecticut Warbler over 18 years at 86 sites in 28 stands of forest in northern Minnesota. We considered the habitat and landscape at three spatial scales (buffer radii of 100, 500, and 1000 m) and regressed combinations of habitat variables with two response variables, the Connecticut Warbler's abundance (the total number of individuals ever recorded at a site or stand, with a zero-inflated negative binomial distribution) and frequency (the number of years recorded out of 18, with logistic regression). From a subset of models retained on the basis of Akaike's information criterion, we calculated model-averaged predictions for each combination of buffer size and response variable. Models based on Connecticut Warbler frequency at the 1000-m buffer perform...

Songbird Use of Floodplain and Upland Forests along the Upper Mississippi River Corridor during Spring Migration

Abstract. The Upper Mississippi River is thought to provide important stopover habitat for migrating landbirds because of its north-south orientation and floodplain forests. The river flows through the Driftless Area of southwestern Wisconsin and southeastern Minnesota where forests are plentiful, yet forests of the floodplain and Driftless Area uplands differ greatly in landscape setting, tree species composition, and topography. We compared landbird assemblages in these upland and floodplain forests over three springs, 2005–2007, using line-transect surveys at randomly selected areas in and within 16 km of the floodplain. We found more species of both transient and locally breeding migrants per survey in floodplain than in upland forest. Detections of transient neotropical migrants did not differ statistically by habitat. Detections of locally breeding neotropical and temperate-zone migrants and transient temperate-zone migrants were greater in floodplain than in upland forest. Between floodplain and up...

Avian mortality at communication towers in the United States and Canada: which species, how many, and where?

Birds migrating to and from breeding grounds in the United States and Canada are killed by the millions in collisions with lighted towers and their guy wires. Avian mortality at towers is highly variable across species, and the importance to each population depends on its size and trajectory. Building on our previous estimate of avian mortality at communication towers, we calculated mortality by species and by regions. To do this, we constructed a database of mortality by species at towers from available records and calculated the mean proportion of each species killed at towers within aggregated Bird Conservation Regions. These proportions were combined with mortality estimates that we previously calculated for those regions. We then compared our estimated bird mortality rates to the estimated populations of these species in the United States and Canada. Neotropical migrants suffer the greatest mortality; 97.4% of birds killed are passerines, mostly warblers (Parulidae, 58.4%), vireos (Vireonidae, 13.4%), thrushes (Turdidae, 7.7%), and sparrows (Emberizidae, 5.8%). Thirteen birds of conservation concern in the United States or Canada suffer annual mortality of 1–9% of their estimated total population. Of these, estimated annual mortality is >2% for Yellow Rail (Coturnicops noveboracensis), Swainson’s Warbler (Limnothlypis swainsonii), Pied-billed Grebe (Podilymbus podiceps), Bay-breasted Warbler (Setophaga castanea), Golden-winged Warbler (Vermivora chrysoptera), Worm-eating Warbler (Helmitheros vermivorum), Prairie Warbler (Setophaga discolor), and Ovenbird (Seiurus aurocapilla). Avian mortality from anthropogenic sources is almost always reported in the aggregate (“number of birds killed”), which cannot detect the species-level effects necessary to make conservation assessments. Our approach to per species estimates could be undertaken for other sources of chronic anthropogenic mortality.

Seasonal variation in stopover site use: Catharus thrushes and vireos in northern Colombia

Migratory routes and stopover sites used by migrant landbirds may vary among seasons and years. Understanding the degree of such variation is an important aspect of migrant ecology, especially in South America, where routes and sites are not well known. We studied stopover site use by two Vireo species and three Catharus species in the Sierra Nevada de Santa Marta in northern Colombia during a two-year period. We used capture totals corrected for mist-net effort and density estimates derived from variable distance transect observations performed at sites located at three different altitudes and thus habitats to describe variation in stopover site use. Four of the five study species showed significant seasonal variation in terms of presence, such that ecologically similar species were present during opposite migration periods; for example, Vireo flavoviridis was an autumn migrant, while Vireo olivaceus was commonest in spring. A similar pattern was observed for Catharus fuscescens and Catharus minimus. We detected differences in density with habitat/altitude, with C. minimus and Catharus ustulatus most abundant in pre-montane forest, while C. fuscescens abundance peaked in lowland forest. At the same altitude, Catharus species were more abundant in pre-montane forest than in shade coffee plantations. The abundance of C. ustulatus varied markedly between years during autumn migration, potentially in association with changes in the prevailing wind conditions. The temporal and spatial variation in stopover site use described here provides important insights into migratory strategies for Neotropical migrants within northern South America, and also regarding the multiple factors that may have shaped these strategies.

Effects of Climate and Exurban Development on Nest Predation and Predator Presence in the southern Appalachian Mountains (U.S.A.)

In the eastern United States, land-use and climate change have likely contributed to declines in the abundance of Neotropical migrant birds that occupy forest interiors, but the mechanisms are not well understood. We conducted a nest-predation experiment in southern Appalachian Mountain forests (North Carolina, U.S.A.) during the 2009 and 2010 breeding seasons to determine the effects of exurban development and temperature on predator presence and the average number of days until eggs in an artificial nest were disturbed by predators. We baited artificial nests with quail (Excalfactoria chinensi) eggs and monitored them for 18 days. We used clay eggs, track plates, and motion-triggered cameras to detect and identify nest predators. The average number of days a nest was undisturbed decreased as mean temperature increased and, to a lesser extent, as the density of buildings increased. Nests on the ground were more often depredated than those in trees, likely due to increased predation by opossum (Didelphis virginiana) and other carnivores. Raccoons (Procyon lotor), opossums, corvids (Corvus brachyrhynchos and Cyanocitta cristata), chipmunks (Tamias striatus), black bears (Ursus americanus), and domestic cats (Felis catus) were the most commonly detected predators. Presence of these predators did not vary as a function of mean temperature. Domestic cats and corvids were detected more frequently in plots with high rather than low densities of buildings. Forest-interior specialists and Neotropical migrants often nest in cool, high-elevation areas with low housing density. These bird species, especially those that nest on the ground, may be most vulnerable to increased nest predation if temperature and exurban development increase at higher elevations as anticipated.

Early seral hardwood vegetation increases adult and fledgling bird abundance in Douglas-fir plantations of the Oregon Coast Range, USA

Recent evidence suggests that population declines of bird species associated with early-successional forest conditions may be associated with reduced quality of breeding habitat. Increasing intensity of forest management on private lands and decreased harvest rates on federal lands in the Pacific Northwest, USA, have resulted in a loss of diverse young forest stands, typically called early seral forest. Previous studies suggest that the amount of early seral broadleaf cover within conifer forests is linked to the composition of foliage-gleaning bird communities. However, information regarding productivity and juvenile use of post-breeding habitat in highly modified plantation habitat is lacking. We examined the relationship between vegetation structure resulting from intensive forest management practices and the abundance of five species of leaf-gleaning, neotropical migrants: orange-crowned warbler ( Oreothlypis celata (Say, 1823)), Wilson’s warbler ( Wilsonia pusilla (A. Wilson, 1811)), MacGillivray’s warbler ( Oporornis tolmiei (J.K. Townsend, 1839)), Swainson’s thrush ( Catharus ustulatus (Nuttall, 1840)), and black-headed grosbeak ( Pheucticus melanocephalus (Swainson, 1827)). All species, except MacGillivray’s warbler, showed positive associations with the amount of early seral hardwood cover as fledglings, breeding adults, or both. However, the relative magnitude of these associations varied, suggesting that other factors may also have influenced avian responses. Abundances of breeding pairs and young are likely to show positive responses to management practices that increase early seral hardwood cover in regenerating stands. If adopted at landscape and regional scales, such practices may positively influence population trends of several declining bird species.

Associations of Small Migratory and Resident Birds with Two Scrub Habitats During Late Winter and Spring in the Northern Chihuahuan Desert, New Mexico

Abstract We used mist nets to survey small migrant and resident birds of scrub habitats in arroyos and adjacent uplands of the northern Chihuahuan Desert during late February–early May 1993–1997. We captured 723 individuals of 49 species. Species diversity was greater in arroyos than in adjacent uplands. Black-throated sparrows (Amphispiza bilineata), white-crowned sparrows (Zonotrichia leucophrys), and green-tailed towhees (Pipilo chlorurus) were captured most frequently. Rates of capture for residents, short-distance migrants, and Neotropical migrants were higher in arroyos than in adjacent shrubland and showed an increase after mid-April caused by an influx of Neotropical migrants heading north to their breeding grounds. Our results suggest that arroyos are important as stopover sites during spring for many migrants, especially Neotropical migrants, as they cross the northern Chihuahuan Desert.

Nest-site selection in the Canada Warbler (Wilsonia canadensis) in central New Hampshire

Reproductive success in birds is largely influenced by nest-site selection. Nest predators are the greatest source of nest failure for most species of birds. Species that nest on the ground may be particularly adapted to maximally conceal nests to reduce the risk of loss to predators. Little is known about nest-site selection in the Canada Warbler ( Wilsonia canadensis (L., 1766)), a small ground-nesting Neotropical migrant. We predicted higher amounts of vegetative cover at successful nests of Canada Warblers compared with unsuccessful nests because detection by predators would decrease with greater cover. We measured vegetative characteristics (concealment, stem densities, ground cover) around each nest and compared these variables between successful and unsuccessful nests and between actual nests and mock nest sites on and off territories. Greater concealment and higher stem densities were the main features surrounding a successful nest site. Nest sites had significantly greater concealment when compared with both random mock nest sites on and off territories. Thus, concealment is important for this ground nester and achieved primarily through thick cover and strategic nest placement in vertical substrate with an inconspicuous opening to the nest cup. Forests with complex ground structure and thickets of small-stemmed woody plants should be targets of conservation when considering how to manage this declining species.

Geographic Origins and Timing of Fall Migration of the Veery in Northern Colombia

Abstract. Establishing migratory connectivity between migratory birds' breeding, wintering, and stopover sites is an important component of their effective conservation and management. For neotropical migrants, geographic origins and migration patterns have been poorly documented. During fall migration of 2009, we identified geographic origins of the Veery (Catharus fuscescens) at stopover sites in the Sierra Nevada de Santa Marta, northern Colombia, by analyzing stable hydrogen isotopes (δD) in feathers and from values expected from a long-term isoscape for North America of δD in feathers. We evaluated the importance of the Sierra Nevada de Santa Marta to the Veery on the basis of the birds' geographic origins and assessed the relationship between timing of migration and geographic origins and age. We estimated that 100 of the 197 individuals captured originated from the southwest and/or the northeast regions of their breeding range, but applying abundance in the breeding range as an informed prior proba...