Intrapopulation variation in diet and habitat use in a Long-distance migrant raptor: a year-round perspective using stable isotopes.

GRANDE, J. M.; GANGOSO, L.; FIGUEROLA, J.; HOBSON, K. H.

San Carlos de Bariloche

Conferencia; I Worldwide Raptor Conference (Raptor Research Foundation Annual Conference 2013 - III Neotropical Raptor Network Conference - WWGBP VII International Conference on Birds of Prey and Owls); 2013

CRUB-Universidad Nacional del Comahue; Neotropical Raptor Network-The Peregrine Fund; World Working Group On Birds Of Prey And Owls; Raptor Research Foundation

Stable isotope ratios in animal tissues are correlated with diet and can vary with geographical area where tissue(s) were formed and so can be used to delineate animal origins or diets.  We used feather δ2H, δ15N and δ13C to explore intrapopulation variability in diet and habitat use in breeding and wintering areas in the Canary Islands Eleonora?s falcon (Falco eleonorae) population.  The species is polymorphic in plumage coloration with a pale and a dark discrete melanin-based colour morphs.  Falcons breed late in the Northern hemisphere allowing birds to feed mostly on migratory passerines during autumn.  Moult starts on the breeding areas and is completed on wintering areas, presumably in Madagascar.  Cluster analyses of feather data showed three isotopic groups: C1 and C2 from wintering areas and a single C3 from breeding areas.  Sexes differed in  δ2H for breeding-area feathers suggesting different diets or timing of moult.  δ15N suggested that dark birds fed from lower trophic level prey than pale birds in the breeding areas in 2006 but not in 2007.  In feathers from wintering areas δ2H differed between years (2007 < 2006).  In 2006, pale birds used habitats with higher δ13C values than dark birds.  Finally, all the bird samples included in C2 were females with particularly positive δ13C.  Our results suggest that diet and/or foraging locations during breeding and wintering differ among sex and colour morphs.