A multi-isotope (δ2H, δ13C, δ15N) approach to establishing migratory connectivity in Palearctic-Afrotropical migrants: An example using Wood Warblers Phylloscopus sibilatrix

Abstract. Wood Warblers Phylloscopus sibilatrixhave declined considerably throughout most of their north and western breeding range in Europe but the causes of this decline are unknown. Declines may be related to factors on the breeding grounds, stopover sites and/or winteringgrounds. We used multi-isotope (δ2H, δ13C, δ15N) measurements of winter-grown feathers of 314 individuals breeding in the Bialowieza Forest (E Poland) to infer where they winteredin sub Saharan Africa over a 4-year period from 2009–2012. We used both aspatial and spatially specific assignment techniques involving a previously developed clustering algorithm related to long-term patterns of precipitation (δ2H) and theoretical plant-based isoscapes( δ13C, δ15N) for Africa. We determined that our breeding population was consistently assigned to the forested region of the Congo basin. Males were more depleted in 13C and 2H and more enriched in 15N than females suggesting potential sexual habitat segregation on the winteringgrounds. We...