Penguins in peril

the midwinter warming of the western Antarctic peninsula is taking its toll on Adelie penguins, say ecologists. A 4 c to 5 c increase in temperature in midwinter is being observed in the region for the past five decades. Ecologists had said that a decrease in sea ice cover due to the warming might be responsible for the recent decline in the number of penguins ( Science , Vol 276, No 5320).

William Fraser, an ecologist at Montana State University, Bozeman, usa, argues that more snow on some islands near Palmer Station in the Antarctic peninsula may be making it harder for the birds to breed. Because a warmer atmosphere holds more moisture and could be causing heavier snowfall, Fraser thinks the Adelie decline could be a sign of warming that is affecting Antarctic ecosystems.

Fraser has been studying penguins on the five islands near Palmer Station for more than two decades to understand why Adelie populations have plummeted from about 15,200 breeding pairs in 1975 to 9,200 today. On Litchfield Island, where the number of breeding pairs dropped 43 per cent between 1972 and 1992, the thriving nesting colonies were concentrated in the northeastern side. The abandoned rookeries, by contrast, were on the southwest side of the island's rocky middle ridge, where more snow accumulates as storms sweep over the islands. The same pattern emerged on nearby islands.

However, scientists have not been able to pinpoint the reason for the declining numbers of penguins as yet.