Inferring the ecology of willow warblers during their winter moult by sequential stable isotope analyses of remiges

Keith Larson, Miriam Liedvogel, Staffan Bensch, Susanne Åkesson, Leonard I. Wassenaar, Keith A. Hobson

Research output: Contribution to journalArticlepeer-review


We present a comparison of feather stable isotope (C-13, N-15) patterns representing the habitat and diet conditions for two subspecies of willow warblers Phylloscopus trochilus that breed in parapatry, but winter in different regions of sub-Saharan Africa. Previous analyses have shown that on average winter moulted innermost primaries (P1) show subspecific differences in N-15 values, although individuals show substantial variation for both C-13 and N-15 within the subspecies. We examined whether corresponding variation in the timing of the winter moult, as reflected by consistent intra-wing correlations for individual's C-13 and N-15 values, could explain some of the previously observed isotopic variation. Further, differential subspecific adaptations to winter precipitation patterns across Africa might result in a variable degree of site fidelity or itinerancy during moult. We found no consistent trend in isotopic values from innermost to outermost primaries, thus inter-individual variation in the timing of moult does not explain the subspecific isotopic variation for P1. Patterns in wing feather C-13 and N-15 values indicated that 41% of the individuals from both subspecies shifted their diet or habitats during winter moult. Importantly, despite well-documented itinerancy in willow warblers during the winter, 59% of the individuals had feather isotope values consistent with stable use of habitats or diets during winter moult. Repeatability analyses suggest that individuals of both subspecies initiate moult in similar habitats from year-to-year while feeding on isotopically similar diets.
Original languageEnglish
Pages (from-to)561-566
JournalJournal of Avian Biology
Issue number6
Publication statusPublished - 2013

Subject classification (UKÄ)

  • Biological Sciences


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