title: Strong migratory connectivity and seasonally shifting isotopic niches in geographically separated populations of a long-distance migrating songbird.
abstract: Whether migratory animals use similar resources during continental-scale movements that characterize their annual cycles is highly relevant to both individual performances and population dynamics. Direct knowledge of the locations and resources used by migrants during non-breeding is generally scarce. Our goal was to estimate migratory connectivity of a small Palaearctic long-distance migrant, the common nightingale Luscinia megarhynchos, and to compare resources used in non-breeding areas with resources used at the breeding grounds. We tracked individuals of three geographically separated populations and characterised their stable isotope niches during breeding and non-breeding over 2 years. Individuals spent the non-breeding period in population-specific clusters from west to central Africa, indicating strong migratory connectivity at the population level. Irrespective of origin, their isotopic niches were surprisingly similar within a particular period, although sites of residence were distant. However, niche characteristics differed markedly between breeding and non-breeding periods, indicating a consistent seasonal isotopic niche shift in the sampled populations. Although nightingales of distinct breeding populations migrated to different non-breeding areas, they chose similar foraging conditions within specific periods. However, nightingales clearly changed resource use between breeding and non-breeding periods, indicating adaptations to changes in food availability.
authors.affiliation: Department of Bird Migration, Swiss Ornithological Institute, Seerose 1, 6204, Sempach, Switzerland, Steffen.Hahn@vogelwarte.ch.
authors.forename: Steffen
authors.initials: S
authors.lastname: Hahn
authors.forename: Valentin
authors.initials: V
authors.lastname: Amrhein
authors.forename: Pavel
authors.initials: P
authors.lastname: Zehtindijev
authors.forename: Felix
authors.initials: F
authors.lastname: Liechti
mesh_terms: D017954:Africa South of the Sahara; D025041:Animal Migration; D000818:Animals; D001947:Breeding; D002031:Bulgaria; D002247:Carbon Isotopes / Q000032:analysis; D017753:Ecosystem; D005260:Female; D005602:France; D007558:Italy; D008297:Male; D009587:Nitrogen Isotopes / Q000032:analysis; D012621:Seasons; D020308:Songbirds
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes