for National Geographic News
Antarctic seabirds are breeding later, because shrinking sea ice is causing their food supplies to dwindle, a new study says.
Adélie penguins, Cape petrels, southern fulmars, and six other species were observed for the study.
The birds, which nest in East Antarctica, have delayed their spring arrival by an average of nine days and egg-laying by an average of two days over the past 50 years, according to polar researchers from the French National Center for Scientific Research in Villiers en Bois, France.
Study authors Christophe Barbraud and Henri Weimerskirch attribute this later breeding activity to decreases in sea ice caused by climate change.
The researchers say the disappearing sea ice, combined with a longer sea-ice season, has interfered with the birds' breeding cycle by reducing the amount of krill and other prey available in early spring in Antarctica. Because Antarctica's seasons are opposite those in the Northern Hemisphere, spring on the icy continent begins in October.
The study is based on data collected at seabird colonies between 1950 and 2004 in Adélie Land, on the eastern edge of the frozen continent.
The findings are published today in the journal Proceedings of the National Academy of Sciences.
Of the nine species studied, some arrived up to 30 days later than they had in previous years.
Despite much later arrivals, the birds are laying their eggs at pretty much the same time as they had in the past. In teh most extreme cases, birds were laying their eggs an average of 3.7 days later in the season than they had been 50 years ago.
SOURCES AND RELATED WEB SITES