title: Is individual consistency in body mass and reproductive decisions linked to individual specialization in foraging behavior in a long-lived seabird?
abstract: Individual specialization in diet or foraging behavior within apparently generalist populations has been described for many species, especially in polar and temperate marine environments, where resource distribution is relatively predictable. It is unclear, however, whether and how increased environmental variability - and thus reduced predictability of resources - due to global climate change will affect individual specialization. We determined the within- and among-individual components of the trophic niche and the within-individual repeatability of δ(13)C and δ(15)N in feathers and red blood cells of individual female southern rockhopper penguins (Eudyptes chrysocome) across 7 years. We also investigated the effect of environmental variables (Southern Annular Mode, Southern Oscillation Index, and local sea surface temperature anomaly) on the isotopic values, as well as the link between stable isotopes and female body mass, clutch initiation dates, and total clutch mass. We observed consistent red blood cell δ(13)C and δ(15)N values within individuals among years, suggesting a moderate degree of within-individual specialization in C and N during the prebreeding period. However, the total niche width was reduced and individual specialization not present during the premolt period. Despite significant interannual differences in isotope values of C and N and environmental conditions, none of the environmental variables were linked to stable isotope values and thus able to explain phenotypic plasticity. Furthermore, neither the within-individual nor among-individual effects of stable isotopes were found to be related to female body mass, clutch initiation date, or total clutch mass. In conclusion, our results emphasize that the degree of specialization within generalist populations can vary over the course of 1 year, even when being consistent within the same season across years. We were unable to confirm that environmental variability counteracts individual specialization in foraging behavior, as phenotypic plasticity in δ(13)C and δ(15)N was not linked to any of the environmental variables studied.
authors.affiliation: Department Biology - Behavioural Ecology & Ecophysiology Group University of Antwerp Campus Drie Eiken, Universiteitsplein 12610 Antwerp (Wilrijk) Belgium; Department of Migration and Immuno-Ecology Max Planck Institute for Ornithology Am Obstberg 178315 Radolfzell Germany; Department of Biology University of Konstanz 78457 Konstanz Germany.
authors.forename: Nina
authors.initials: N
authors.lastname: Dehnhard
authors.affiliation: Department Biology - Behavioural Ecology & Ecophysiology Group University of Antwerp Campus Drie Eiken, Universiteitsplein 1 2610 Antwerp (Wilrijk) Belgium.
authors.forename: Marcel
authors.initials: M
authors.lastname: Eens
authors.affiliation: Laboratory of Oceanology MARE Centre University of Liège B6C, Sart Tilman 4000 Liège Belgium.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Sturaro
authors.affiliation: Laboratory of Oceanology MARE Centre University of Liège B6C, Sart Tilman 4000 Liège Belgium.
authors.forename: Gilles
authors.initials: G
authors.lastname: Lepoint
authors.affiliation: Department Biology - Behavioural Ecology & Ecophysiology Group University of Antwerp Campus Drie Eiken, Universiteitsplein 12610 Antwerp (Wilrijk) Belgium; Department of Migration and Immuno-Ecology Max Planck Institute for Ornithology Am Obstberg 178315 Radolfzell Germany; Department of Biology University of Konstanz 78457 Konstanz Germany.
authors.forename: Laurent
authors.initials: L
authors.lastname: Demongin
authors.affiliation: Department of Migration and Immuno-Ecology Max Planck Institute for Ornithology Am Obstberg 178315 Radolfzell Germany; Department of Biology University of Konstanz 78457 Konstanz Germany; Department of Animal Ecology & Systematics Justus-Liebig University Gießen Heinrich-Buff-Ring 38D-35392 Gießen Germany.
authors.forename: Petra
authors.initials: P
authors.lastname: Quillfeldt
authors.affiliation: Department Biology - Behavioural Ecology & Ecophysiology Group University of Antwerp Campus Drie Eiken, Universiteitsplein 12610 Antwerp (Wilrijk) Belgium; Department of Migration and Immuno-Ecology Max Planck Institute for Ornithology Am Obstberg 178315 Radolfzell Germany; Department of Biology University of Konstanz 78457 Konstanz Germany.
authors.forename: Maud
authors.initials: M
authors.lastname: Poisbleau
keywords: Clutch mass; Eudyptes chrysocome; Southern Annular Mode; Southern Oscillation Index; environmental variability; global climate change; phenology; sea surface temperature; southern rockhopper penguin; stable isotopes