Science/Medicine : Swallows Spread Eggs Around, Study Finds

A study of cliff swallows in Nebraska has found that they truly do not put all their eggs in one basket.

Some birds slipped eggs into the nests of other swallows, perhaps as a precaution in case their own nest was destroyed, researchers said.

They said the study marks the first clear evidence in birds of moving eggs to “parasitize” other nests. In one case, a swallow that showed up at a neighboring nest with an egg in its beak was driven off within 10 seconds, but the egg stayed behind. In another, the egg was deposited without incident while the nest’s owner was absent, according to the researchers.

Results of a five-year study of six colonies near Ogallala, Neb., were reported by Charles R. and Mary Bomberger Brown of Yale University in the current issue of Nature magazine.

The researchers also marked 204 eggs in 50 nests, and found two days later that three of the nests had acquired a marked egg from a neighboring nest. Other observations suggested a swallow may sometimes remove an egg from a neighboring nest before donating an egg of its own, they said.