Overwintering habitat links to summer reproductive success: intercontinental carry-over effects in a declining migratory bird revealed using stable isotope analysis

Abstract

ABSTRACTCapsule: Breeding success in female Pied Flycatchers Ficedula hypoleuca is related to isotopic signature of feathers grown in Africa, suggesting wintering habitat links to breeding performance 5000 km away.Aims: Better understanding of inter-seasonal carry-over effects is a research priority, especially for declining migrants. We use stable isotope analysis to relate Pied Flycatcher winter habitat to summer reproductive success.Methods: Flycatchers were captured in three UK woodlands in 2013–15. An Africa-grown tertial was trimmed and analysed using Isotope Ratio Mass Spectrometry to quantify Nitrogen-15 (δ15N) and Carbon-13 (δ13C). In total, 135 samples were taken from 80 individuals.Results: Wintering δ15N and δ13C differed significantly between years. δ13C correlated with lay date, such that birds with lower carbon levels (indicative of more mesic habitat) bred earlier. There was a significant correlation between wintering δ13C and productivity after allowing for year, site and lay date; birds with low δ13C were more successful. This suggests δ13C links productivity directly as well as indirectly through phenological effects. δ15N did not relate to phenology or productivity.Conclusion: This is the first evidence of carry-over effects between geographical regions for a European passerine. Conservation measures should focus on all aspects of seasonal cycles, not just breeding grounds.