Intraspecific variability in isotopic composition of a monomorphic seabird, the Common Tern ( Sterna hirundo ), at wintering grounds

MARIANO-JELICICH, ROCÍO; LAMACCHIA, PAOLA; MADRID, ENRIQUE A.

EMU

CSIRO PUBLISHING

Lugar: Collingwood; Año: 2019 vol. 119 p. 176 - 185

0158-4197

Understanding sex differences in foraging behaviour has important implications for breedingbiology and population ecology. This requires the evaluation of segregation throughout theannual cycle, including the non-breeding period. We studied the diet and foraging strategies ofthe Common Tern (Sterna hirundo) at an intraspecific level by sampling birds during twoconsecutive non-breeding periods in Punta Rasa, Buenos Aires Province, Argentina. Blood sampleswere taken for sex determination and carbon and nitrogen stable isotope analysis. Noisotopic difference was observed between years, but higher isotopic values occurred duringlate non-breeding period. Carbon and nitrogen isotopic values were similar between sexes;however, differences were observed in standard ellipse analyses, considered to represent isotopicniches. Even though the Bayesian ellipse areas overlapped, females showed wider isotopic nichesthroughout the non-breeding period. This could be related to different feeding strategies,foraging areas or migratory stopover sites at either intraspecific or individual levels. Diet contributionsof different prey categories estimated through mixing model analyses suggested ahigher contribution of estuarine fish than of marine pelagic species. These results highlight theimportance of stable isotope analyses as a complementary methodology to traditional dietstudies, particularly during the non-breeding period.