The annual advance and retreat of pack ice may be the major determinant of spatial and temporal changes in the structure, function, and distribution of Antarctic penguin populations. Satellite records, from 1973 onwards, indicate that winter pack ice reaches its maximum extent on 6-8 year cycles. These interannual cycles in pack ice extent may have significant impacts on all levels of the marine food web, thereby affecting the penguins' reproductive success, survival, and recruitment patterns which are factors regulating penguin populations. This project continues a comparative study of the population biology of Adelie, Gentoo, and Chinstrap Penguins (Pygoscelis adeliae, P. papua, and P. antarctica, respectively) at Admiralty Bay, King George Island, South Shetland Islands, Antarctica. The Pygoscelis species are the major predators of Krill (Euphausia superba) in the Antarctic Peninsula region and are the primary species used as monitors of fishery activities in this area. To thoroughly understand the structure and function of the Antarctic marine ecosystem, it is imperative to determine the impact of environmental variation on the structure and regulation of key trophic level predators such as the Pygoscelis penguins. This research will contribute such information.
