Faster Than a Speeding Songbird

New research shows migrating songbirds completing transcontinental journey much faster than previously thought

Purple Martin

iStockPhoto

You won't find geolocator backpacks in the North Face catalog anytime soon, but if you fly south for the winter you may notice one strapped to the back of a migrating songbird. That's how an inventive group of researchers have been tracking the speed and location of purple martins and wood thrushes flying from Pennsylvania to South America and back. What they've have found is truly astonishing.

The study, funded in part by the National Geographic Society, concluded that songbirds fly a whopping 3 times faster than expected. Data from the geolocators indicated that the birds can fly in excess of 311 miles per day, as reported in the Feb. 13 issue of the journal Science. Previous studies estimated their flight performance at roughly 93 miles per day.

Researchers also found that overall migration rates are two to six times more rapid in spring than they are in autumn. For example, one purple martin took 43 days to reach Brazil during fall migration, but in spring it returned to its breeding colony in only 13 days. Prolonged stopovers during fall migration were blamed for the relatively lackadaisical pace. The purple martins had a stopover of three to four weeks in the Yucatan before continuing to Brazil, while the wood thrushes stopped two to four weeks before continuing migration.

The geolocators, which are smaller than a dime, detect light, allowing researchers to estimate birds' latitude and longitude by recording sunrise and sunset times. The devices 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, a professor of biology in York's Faculty of Science & Engineering. "We're excited to achieve this scientific first."