Jocelyn Kaiser, Ecology Editor of Science, summarizes recent research suggesting that Adelie penguin populations are decreasing due to a 4 to 5 degree Celsius warming in the western Antarctic Peninsula over the last 50 years. William Fraser of Montana State University has suggested that increased snowfall on the five islands near Palmer Station due to higher temperatures is leading to more loss of eggs and chicks because of snow and slush. Another suggested cause of the decline in numbers of Adelie penguins is the reduction of sea ice (also due to regional warming) which limits feeding opportunities for these penguins who preferentially feed along ice edges.
Reference
For more information, see Science, 276, 1790 (20 June 1997).