Stable isotope analysis provides new information on winter habitat use of declining avian migrants that is relevant to their conservation

Evans, K.L., Newton, J. , Mallord, J.W. and Markman, S. (2012) Stable isotope analysis provides new information on winter habitat use of declining avian migrants that is relevant to their conservation. PLoS ONE, 7(4), e34542. (doi: 10.1371/journal.pone.0034542)

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Winter habitat use and the magnitude of migratory connectivity are important parameters when assessing drivers of the marked declines in avian migrants. Such information is unavailable for most species. We use a stable isotope approach to assess these factors for three declining African-Eurasian migrants whose winter ecology is poorly known: wood warbler Phylloscopus sibilatrix, house martin Delichon urbicum and common swift Apus apus. Spatially segregated breeding wood warbler populations (sampled across a 800 km transect), house martins and common swifts (sampled across a 3,500 km transect) exhibited statistically identical intra-specific carbon and nitrogen isotope ratios in winter grown feathers. Such patterns are compatible with a high degree of migratory connectivity, but could arise if species use isotopically similar resources at different locations. Wood warbler carbon isotope ratios are more depleted than typical for African-Eurasian migrants and are compatible with use of moist lowland forest. The very limited variance in these ratios indicates specialisation on isotopically restricted resources, which may drive the similarity in wood warbler populations' stable isotope ratios and increase susceptibility to environmental change within its wintering grounds. House martins were previously considered to primarily use moist montane forest during the winter, but this seems unlikely given the enriched nature of their carbon isotope ratios. House martins use a narrower isotopic range of resources than the common swift, indicative of increased specialisation or a relatively limited wintering range; both factors could increase house martins' vulnerability to environmental change. The marked variance in isotope ratios within each common swift population contributes to the lack of population specific signatures and indicates that the species is less vulnerable to environmental change in sub-Saharan Africa than our other focal species. Our findings demonstrate how stable isotope research can contribute to understanding avian migrants' winter ecology and conservation status.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Newton, Dr Jason
Authors: Evans, K.L., Newton, J., Mallord, J.W., and Markman, S.
College/School:College of Science and Engineering > Scottish Universities Environmental Research Centre
Journal Name:PLoS ONE
Publisher:Public Library of Science
ISSN (Online):1932-6203
Published Online:05 April 2012
Copyright Holders:Copyright © 2012 Evans et al.
First Published:First published in PLoS ONE 2012 7(4):e34542
Publisher Policy:Reproduced with the permission of the author, distributed under the terms of the Creative Commons Attribution Non-Commercial License

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