Songbirds fly thrice as fast as estimated

February 13th, 2009 - 4:53 pm ICT by IANS  

Toronto, Feb 13 (IANS) Songbirds fly thrice as fast as estimated, scientists have found after tracking their movements for the first time with the help of tiny flight geolocators.
The devices, smaller than a dime, are mounted on birds’ backs by looping thin straps around their legs. The weight of the geolocator rests at the base of the bird’s spine, so as not to interfere with its balance.

“Never before has anyone been able to track songbirds for their entire migratory trip,” said study author Bridget Stutchbury, professor of biology in York’s Faculty of Science & Engineering.

“We’re excited to achieve this scientific first,” she said.

Songbirds, the most common type of bird in our skies, are too small for conventional satellite tracking.

Stutchbury and her team mounted miniaturised geolocators on 14 wood thrushes and 20 purple martins, breeding in Pennsylvania during 2007, tracking the birds’ autumnal takeoff, migration to South America, and journey back to North America.

In the summer 2008, they retrieved the geolocators from five wood thrushes and two purple martins and reconstructed individual migration routes and wintering locations.

Data from the geolocators indicated that songbirds can fly in excess of 500 km (311 miles) per day, reports Stutchbury. Previous studies estimated their flight performance at roughly 150 km (93 miles) per day.

The study, partly funded by the National Geographic Society, found that songbirds’ overall migration rate was two to six times more rapid in spring than in fall.

For example, one purple martin took 43 days to reach Brazil during fall migration, but in spring returned to its breeding colony in only 13 days. Rapid long-distance movement occurred in both species, said Stutchbury.

“We were flabbergasted by the birds’ spring return times. To have a bird leave Brazil on April 12 and be home by the end of the month was just astounding. We always assumed they left sometime in March,” she said.

Researchers also found that prolonged stopovers were common during autumnal migration. The purple martins, which are members of the swallow family, had a stopover of three to four weeks in the Yucatan before continuing to Brazil, said a York release.

The results were published in the Friday issue of Science.

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