Comparison of long-term trends in abundance, recruitment and reproductive success of five populations of Pygoscelis penguins
in the South Shetland Islands, Antarctica

Responses of predator populations to environmental variability in the Antarctic have tended to exhibit site- and species-specific differences owing to variation in geographic settings and predator life-history strategies. Five populations of Pygoscelis penguins from King George Island and Livingston Island, South Shetland Islands, Antarctica, were examined to compare up to 25 years of data on the responses of sympatric congeners to recent changes in their Antarctic ecosystem. We used simple linear regression and correlation analyses to detect and compare trends in indices of population abundance, recruitment, and summer breeding performance of the Adélie (P. adeliae), gentoo (P. papua), and chinstrap penguins (P. antarctica). In general, the different trends in abundance and recruitment indices for each species, despite generally similar indices of summer performance, point to life-history-specific vulnerabilities during winter that contribute to differential survival rates of the penguins. In particular, significant relationships between indices of penguin and krill recruitment suggest that penguin populations in the South Shetland Islands may live under an increasingly krill-limited system that has disproportionate effects on the survival of juvenile birds.