Interannual study of chinstrap penguin's diet and reproductive success at Laurie Island, South Orkney Islands, Antarctica

Inter-annual variability in the diet of Chin-strap penguins (Pygoscelis antarctica) at Laurie Island, South Orkney Islands was examined based on stomach contents of adults coming ashore during the 1997/1998-2001/2002 breeding seasons. Krill (Euphausia superba) dominated the diet either as frequency of occurrence (in 100% of samples), number (> 99%), and percentage contribution in weight (> 99.5%). Other prey items were minor but did vary between years. The contribution in weight of fish, amphipods and cephalopods ranged between 0.01-0.5, < 0.01-0.14 and 0-0.03, respectively. Although minor components varied slightly along the years, the weight of stomach contents was significantly different. It was found that for a given weight the maximum observed percentage of undigested krill resulted negatively correlated with the stomach contents total weight. The proportion of whole krill observed in individual penguins, expressed as a fraction of the maximum corresponding to its weight was used to characterize the prevailing conditions in each season.