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Copyright of Ornithological Applications is the property of Oxford University Press / USA and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Temporal variation in the connectivity of populations of migratory animals has not been widely documented, despite having important repercussions for population ecology and conservation. Because the long-distance movements of migratory animals link ecologically distinct and geographically distant areas of the world, changes in the abundance and migratory patterns of species may reflect differential drivers of demographic trends acting over various spatial scales. Using stable hydrogen isotope analyses (δ2H) of feathers from historical museum specimens and contemporary samples obtained in the field, we provide evidence for an approximately 600 km northward shift over 45 years in the breeding origin of a species of songbird of major conservation concern (blackpoll warbler, Setophaga striata) wintering in the foothills of the eastern Andes of Colombia. Our finding mirrors predictions of range shifts for boreal-breeding species under warming climate scenarios and habitat loss in the temperate zone, and underscores likely drivers of widespread declines in populations of migratory birds. Our work also highlights the value of natural history collections to document the effects of global change on biodiversity. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Field Ornithology is the property of Resilience Alliance and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aim In birds, patterns of migratory connectivity are influenced by landscape structure experienced throughout the annual cycle. Assessing how landscape patterns drive the movements and distributions of migratory species is important for understanding the evolution of migration and determining conservation priorities. We determined migratory connectivity in the Canada Warbler ( Cardellina canadensis), a declining Neotropical migratory bird, and evaluated the degree to which the Andean mountains influence winter population distribution in this montane forest specialist. Location Seven study regions across the Western, Central, and Eastern Andes of Colombia. Methods We inferred breeding and natal origins of Canada Warblers overwintering in Colombia by analysing stable hydrogen isotope values (δ2H) in feathers and assigning wintering populations to breeding origins using an established feather δ2H isoscape for North America. Results We found strong evidence for parallel migration between breeding and wintering sites, giving rise to moderately strong migratory connectivity between breeding and wintering regions. The model best explaining population distribution in the Colombian Andes implied that populations were most similar within basins or valleys. Such segregation is notable, given that basins are separated by less than 300 km on the wintering grounds, while breeding populations may be separated by more than 3000 km from east to west. Main conclusions Our results suggest that the high spine of each Andean cordillera acts to shape the winter distribution of individuals from different breeding populations. To our knowledge, this is the first demonstration that the topography of the Andean mountains can act to shape the winter distribution of populations of a migratory bird. The strength of migratory connectivity found in Canada Warblers may inhibit evolutionary responses to environmental change, and the more rapid population declines recorded in some eastern breeding populations may be related to habitat loss and local environmental conditions in the Eastern Andes, where individuals from these populations were more likely to overwinter. [ABSTRACT FROM AUTHOR]

Geographic convergence during migration influences the extent to which animal populations may experience carry‐over effects across periods of the annual cycle. When most individuals of a population share geographic areas during a given priod, carry‐over effects are likely stronger than when individuals occupy multiple areas. We used genetic data and stable isotope (δ2H) measurements from feathers and claws to describe the likely breeding and wintering geographic origins of a long‐distance migratory songbird (Gray‐cheeked Thrush, Catharus minimus) moving through northern Colombia in spring and fall migration. Furthermore, we used these data coupled with regional occupancy surveys to assess whether individuals from various breeding populations converge during migration and evaluated whether geographic origin, age, or sex affected stopover strategies. We found that range‐wide breeding populations of Gray‐cheeked Thrush converged in northern Colombia in an area spanning <1% of the breeding range, especially during a prolonged spring stopover in the Sierra Nevada de Santa Marta. Breeding (but not winter) origin, sex, and age influenced arrival date and body condition upon arrival at stopover sites where populations converged. Birds from more northerly breeding latitudes, males and adults generally arrived earlier and in lower body condition than those with more southerly breeding origins, females, and juveniles. Our work and other studies suggest that areas in northern Colombia may function as ecological bottlenecks for Gray‐cheeked Thrush because they concentrate individuals from across the breeding range, provide critical resources, and impose constraints during migration. Future studies quantifying the effects of high‐convergence areas on fitness and survival of individuals and their demographic consequences are required to assess their roles as ecological bottlenecks. [ABSTRACT FROM AUTHOR]