Is individual consistency in body mass and reproductive decisions linked to individual specialization in foraging behavior in a long-lived seabird?

摘要

Individual specialization in diet or foraging behavior within apparently generalistpopulations has been described for many species, especially in polar andtemperate 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 climatechange will affect individual specialization. We determined the within- andamong-individual components of the trophic niche and the within-individualrepeatability of d13C and d15N in feathers and red blood cells of individualfemale southern rockhopper penguins (Eudyptes chrysocome) across 7 years. Wealso investigated the effect of environmental variables (Southern Annular Mode,Southern Oscillation Index, and local sea surface temperature anomaly) on theisotopic values, as well as the link between stable isotopes and female bodymass, clutch initiation dates, and total clutch mass. We observed consistent redblood cell d13C and d15N values within individuals among years, suggesting amoderate degree of within-individual specialization in C and N during the prebreedingperiod. However, the total niche width was reduced and individualspecialization not present during the premolt period. Despite significant interannualdifferences in isotope values of C and N and environmental conditions,none of the environmental variables were linked to stable isotope values andthus able to explain phenotypic plasticity. Furthermore, neither the within-individualnor among-individual effects of stable isotopes were found to be relatedto female body mass, clutch initiation date, or total clutch mass. In conclusion,our results emphasize that the degree of specialization within generalist populationscan vary over the course of 1 year, even when being consistent within thesame season across years. We were unable to confirm that environmental variabilitycounteracts individual specialization in foraging behavior, as phenotypicplasticity in d13C and d15N was not linked to any of the environmental variablesstudied.