Ancient penguin nests tell climate tale.

Although best known for its tuxedo-like plumage and ungainly waddle, the comical Adelie penguin is actually one of the world's hardiest birds, able to nest along the harsh Antarctic coastline farther south than most other penguin species. Taking advantage of the Adelie's unusual housing habits, two Italian researchers have developed a record of how the Antarctic coast has warmed and cooled over the last 13,000 years.

The scientists, from the University of Pisa and the University of Milan, used carbon-14 dating to determine the age of ancient Adelie bones, feathers, eggs, and guano. The researchers charted the regional climate history by tracking when the birds abandoned nesting sites. Because the penguins feed in the ocean, they typically set up colonies near open water and must establish new nests when the coastline becomes covered in year-around ice. In the Ross Sea region, the scientists found that Adelies colonized much of the coast between 4,000 and 3,000 years ago, indicating a decrease in sea ice during that period, they report in the January GEOLOGY.