On eating and being eaten

The changing diet of polar bears, with a new emphasis on the eggs of snow geese:

David Iles, a graduate student at Utah State University, who has been working at La Pérouse Bay for several years, set out cameras to observe goose nests and caught the bears in the act. He now has 40 cameras set up over a stretch of tundra. They take photographs every two minutes and shoot a burst of 30 images when an animal walks in front of the camera.

In addition to capturing photographs of bears consuming eggs last season, the cameras caught cranes, wolves, eagles and foxes eating. “Everything seems to love eggs out here,” he said.

One goose or one nest may not seem like much. But polar bears are gluttons. Dr, Rockwell described one case in which a bear ate about 1,200 eggs — of eider ducks, in this case — in four days. He said Dr. Gormezano had calculated that a clutch of four eggs would amount to 825 calories, the equivalent of one and a half Big Macs. Three hundred four-egg clutches would be 247,500 calories, or about 10 percent of a bear’s yearly nutritional needs.

The ruddy turnstone

New lightweight tracking devices allow scientists to follow a tiny bird's round-the-world migration:

Tracker devices can be fitted on birds either by fixing them to a leg or by sticking them to the back. All the ruddy turnstone had them attached to legs because tests showed that after spending the Australasian summer fattening up to their maximum weight of about 190g they were "as round as tennis balls" and the backpack style wouldn't stay on.