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Backpack-wearing birds teach researchers about migration

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Small songbirds, like the purple martin (at right) and thrushes, can migrate far faster than scientists have previously believed, according to a new study published in the journal Science.

The birds can travel up to 311 miles each day during their annual migration, and researchers (who tracked the birds using miniature geolocators, about the size of a dime, attached to the birds’ backs like tiny backpacks) found that they travel two to six times faster on the way up to North America in the spring as they do on the trip down to Central and South America in the fall. One female martin flew 4,660 miles, from the Amazon basin north to Pennsylvania, in only 13 days. Our colleague Thomas H. Maugh II has the details:

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[Ornithologist Bridget Stutchbury of York University in Toronto] and her colleagues attached the sensors to 14 wood thrushes and 20 purple martins at their breeding grounds in northwestern Pennsylvania. The following spring, the researchers were able to recapture five thrushes and two martins. Two more thrushes came back but nested too high for the team to recapture. As for the rest, ‘we have no idea what happened to them,’ Stutchbury said. ‘We don’t know whether it was just bad luck or the birds were slowed down by the weight of the devices.’ The martins flew the 1,500 miles south to the Yucatan Peninsula in five days, then stopped over for three or four weeks before continuing on to the Amazon basin. The thrushes spent one to two weeks in the southeastern United States before continuing on to their wintering grounds in a narrow strip along the coast of Honduras or Nicaragua.

‘We knew that purple martins went to Brazil and wood thrush went to Central America,’ Stutchbury told the New York Times. ‘But the details of how an individual gets there, what routes they take, how fast they fly, how often they stop to rest -- these are the kinds of details we have never been able to have.’

Researchers have already placed the tiny tracking devices, which have previously been used on larger birds such as shearwater gulls, on other tiny birds, including bobolinks, seaside sparrows and other thrush species.

-- Lindsay Barnett

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