Scientists Puzzled by Synchrony of Migratory Birds

LONDON (Reuters) - They rarely see each other, spend winters in different countries and don't communicate for long periods but pairs of a species of Icelandic migratory birds know exactly when to return home to breed.

The couples of black-tailed godwits somehow manage to coordinate their journeys, from different countries up to 1,000 km apart, to arrive back at their Iceland breeding grounds within about three days of each other.

"When males and females from a pair arrive back on their breeding territory in the spring, they do so with remarkable synchrony," Jill Gill, of the University of East Anglia said in an interview.

"We're astonished by it."

Scientists had assumed that males and females of migratory bird species stayed together during the winter and traveled back with each other to their breeding grounds.

"In this particular species, the males and females are going to completely different locations, often different countries, so they are wintering on average 1,000 miles apart," said Gill, who reported the findings in the science journal Nature.

"And yet they are getting back somehow to the breeding ground within two or three days of one another.""

"We have had two cases of divorce," said Gill. "In both cases the female got back before the male."

Tired of waiting, both females mated with other males.