The researchers, who attached radio transmitters to thrushes and then followed them by car at night, said their findings help explain how birds fly across the equator at night without getting lost.
The experiment, published in the journal Science, is one of the first to use free-flying birds instead of captive birds in a laboratory. WASHINGTON (Reuters) - A sunset may do more than refresh the soul -- it could recalibrate the internal compasses of migrating songbirds, U.S. and German researchers reported on Thursday.
The researchers, who attached radio transmitters to thrushes and then followed them by car at night, said their findings help explain how birds fly across the equator at night without getting lost.
The experiment, published in the journal Science, is one of the first to use free-flying birds instead of captive birds in a laboratory.
Martin Wikelski of Princeton University in New Jersey and colleagues in the United States and Germany first caught several dozen thrushes and attached tiny radio transmitters to them.
Knowing that birds use magnetic fields to orient themselves, they put some birds in an artificial magnetic field to confuse them, and then let them all go.
The birds that had not been tricked flew north, as they usually do, but the birds exposed to the artificial field flew west, the researchers said.
The next evening, all the birds were free to see the sun. Subsequently, all flew north again.
"We suggest that birds orient with a magnetic compass calibrated daily from twilight cues," the researchers wrote.
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