title: Provenance does matter: links between winter trophic segregation and the migratory origins of European robins.
abstract: Amongst migratory species, it is common to find individuals from different populations or geographical origins sharing staging or wintering areas. Given their differing life histories, ecological theory would predict that the different groups of individuals should exhibit some level of niche segregation. This has rarely been investigated because of the difficulty in assigning migrating individuals to breeding areas. Here, we start by documenting a broad geographical gradient of hydrogen isotopes (δ2H) in robin Erithacus rubecula feathers across Europe. We then use δ2H, as well as wing-tip shape, as surrogates for broad migratory origin of birds wintering in Iberia, to investigate the ecological segregation of populations. Wintering robins of different sexes, ages and body sizes are known to segregate between habitats in Iberia. This has been attributed to the despotic exclusion of inferior competitors from the best patches by dominant individuals. We find no segregation between habitats in relation to δ2H in feathers, or to wing-tip shape, which suggests that no major asymmetries in competitive ability exist between migrant robins of different origins. Trophic level (inferred from nitrogen isotopes in blood) correlated both with δ2H in feathers and with wing-tip shape, showing that individuals from different geographic origins display a degree of ecological segregation in shared winter quarters. Isotopic mixing models indicate that wintering birds originating from more northerly populations consume more invertebrates. Our multi-scale study suggests that trophic-niche segregation may result from specializations (arising in the population-specific breeding areas) that are transported by the migrants into the shared wintering grounds.
authors.affiliation: MARE, Marine and Environmental Sciences Centre, ISPA-Instituto Universitário, Rua Jardim do Tabaco 34, 1149-041, Lisbon, Portugal. paulo.catry@gmail.com.
authors.forename: Paulo
authors.identifier: http://orcid.org/0000-0003-3000-0522
authors.initials: P
authors.lastname: Catry
authors.affiliation: MARE, Marine and Environmental Sciences Centre, Department of Life Sciences, University of Coimbra, 3000-456, Coimbra, Portugal.
authors.forename: Ana R
authors.initials: AR
authors.lastname: Campos
authors.affiliation: CESAM and Departamento de Biologia Animal, Faculdade de Ciências da Universidade de Lisboa, Lisbon, Portugal.
authors.forename: José Pedro
authors.initials: JP
authors.lastname: Granadeiro
authors.affiliation: CIBIO/UP, Centro de Investigação em Biodiversidade e Recursos Genéticos, Universidade do Porto, Porto, Portugal.|Molecular Ecology and Evolution Lab, MEMEG, Department of Biology, University of Lund, Lund, Sweden.
authors.forename: Júlio M
authors.initials: JM
authors.lastname: Neto
authors.affiliation: MARE, Marine and Environmental Sciences Centre, Department of Life Sciences, University of Coimbra, 3000-456, Coimbra, Portugal.
authors.forename: Jaime
authors.initials: J
authors.lastname: Ramos
authors.affiliation: NERC Life Sciences Mass Spectrometry Facility, SUERC, Rankine Avenue, East Kilbride, Glasgow, G75 0QF, UK.|Centre for Ecology and Conservation, University of Exeter, Cornwall Campus, Exeter, TR10 9FE, UK.
authors.forename: Jason
authors.initials: J
authors.lastname: Newton
authors.affiliation: Centre for Ecology and Conservation, University of Exeter, Cornwall Campus, Exeter, TR10 9FE, UK.
authors.forename: Stuart
authors.initials: S
authors.lastname: Bearhop
mesh_terms: D025041:Animal Migration; D000818:Animals; D005241:Feathers / Q000737:chemistry; D009587:Nitrogen Isotopes; D012621:Seasons; D020308:Songbirds
chemical_list: D009587:Nitrogen Isotopes
keywords: Ecological segregation; Erithacus rubecula; Migration; Seasonal matching; Stable isotopes