Subcolony characteristics and breeding performance in the chinstrap penguin Pygoscelis antarctica
Published: Volume 53(1), June 2006. Pages 19-29.
Aims: Subcolonies of penguins differ markedly in physical characteristics and in breeding success. Subcolony size is the best studied subcolony characteristic and has been suggested to be an important factor explaining the variation in reproductive success. Small subcolonies generally have lower breeding success, probably because they suffer from worse environmental conditions. It is likely that lower quality individuals also occupy smaller subcolonies, which in turn affects breeding success. However, results are not always consistent, and other subcolony characteristics may mediate breeding success. In the present study, the relationship is investigated between physical subcolony characteristics (slope, isolation and size) and several variables indicative of individual quality and breeding success in the chinstrap penguin Pygoscelis antarctica.
Location: The study was performed in the Vapour Col chinstrap penguin colony on Deception Island (South Shetlands Archipelago, 63° 00' S, 60° 40' W) during the austral 2002-03 breeding season.
Methods: The slope, the degree of isolation and the size (number of nests) of 22 randomly selected subcolonies were measured. Variables indicating individual quality were considered in 10 nests of each subcolony: parental body size (bill length, bill depth, flipper length), nest size and egg size, and variables indicating breeding success: hatching date and hatching success.
Results: Both isolated and sloped subcolonies were smaller in size, and were occupied by male parents with shorter bills and less bill depth respectively. Isolated subcolonies also showed a delayed hatching date and lower hatching success and females of more sloped subcolonies laid smaller eggs. Nest size was larger in isolated subcolonies and smaller in sloped subcolonies.
Conclusions: This study indicates that physical characteristics of subcolonies, such as the degree of isolation and slope, rather than just size, affect breeding success of chinstrap penguins. It is also suggested that nest size could be an indicator of individual quality only if it is compared within the same subcolony or if the effect of subcolony is taking into account.