“Diet and sex differentiation in southern rockhopper penguins (Eudyptes chrysocome chrysocome) in Staten Island, Argentina”

A RAYA REY; A SCHIAVINI

Ushuaia, Tierra del Fuego, Argentina

Conferencia; V International Penguin Conference; 2004

CADIC- CONICET

Southern rockhopper penguins as all the crested species are sexually dimorphic and each sex has specific breeding duties. During the brooding period only females feed their chicks while both parents did it during the crèche stage. The stomach contents of 20 females during brooding and 10 from each sex during the crèche stage in 2002/2003 breeding season were analysed and the diet and stages and sex differences studied. Moreover, the foraging trips duration in both periods was assessed by an automated reading system that detected breeding birds, which were injected with transponders in previous seasons. In both stages a mixture of crustaceans, cephalopods and fish larvae and juveniles were found. Nevertheless, not all the prey species remained the same in both stages and also the frequency of occurrence and composition by number varied. We found also differences in prey species and composition by number between sexes during the crèche period. Given the duration of the foraging trips, the foraging areas were almost the same in both stages. However, almost twice the numbers of penguins were foraging during the crèche period. The diet and differences found between stages and sexes related with the habitat, sexual dimorphism and competition are discussed.