Intraspecific variation in Chinstrap Penguin’s (Pygoscelis antarcticus) trophic niche in two islands from the South Shetlands Archipelago, Antarctica

We assessed intraspecific variation in the Chinstrap penguin’s trophic niche through stable isotope analysis in two latitudinally distinct islands, in order to evaluate differences in foraging behavior among and within populations. Whole blood (n = 24) and body feathers (n = 24) were sampled in breeding colonies at Elephant and Livingston Islands during the 2013/14 austral summer, and both tissues were analyzed for bulk δ13C and δ15N stable isotopes. Blood isotope values were used as a proxy for the trophic niche used during the incubation period, while feathers represented the post-breeding period. We extracted isotopic niche metrics, and tested for significant differences in δ13C and δ15N values between the islands for both periods. In order to investigate differences within populations, we tested for intersexual differences for both δ13C andδ15N values, and calculated the coefficient of variation for each population to determine individual variation in trophic niche. Our results show that Chinstrap penguins have variation in the width of their trophic niche between different periods of the annual cycle and among distinct breeding sites. We found significant differences in individual variation between the two periods, and the absence of intersexual differences in δ13C and δ15N values. Overall, breeding individuals of Elephant Island presented enriched δ13C values compared to those of Livingston during incubation, suggesting that the former consumed more nearshore/benthic based resources. δ15N values were more variable in Livingston Island during the post-breeding period, suggesting that individuals consumed a wider variety of prey during this period. Our results contribute to the knowledge on Chinstrap penguin’s trophic plasticity in Antarctica.