'Amazing' songbird migration patterns

Songbirds fly faster and further than anyone has realised, according to scientists who have tracked their migration routes for the first time. The researchers said they were "flabbergasted" by the findings, which will help biologists predict how climate change and habitat loss will affect the birds.

Songbirds are the most common type of bird, but until now little has been known about their annual journeys because they are too small to carry satellite-tracking devices. Instead, the scientists strapped tiny backpacks that record sunrise and sunset times onto wood thrushes and purple martins, and this data allowed them to plot the birds' flights between Pennsylvania and South America.

The researchers found the birds could fly more than 300 miles per day. In contrast, previous studies had put their daily range at under 100 miles per day. The study also discovered that the birds flew much faster on their journey home in spring: one purple martin, a type of swallow, took 43 days to reach Brazil on its autumn outward leg but in spring returned to its breeding colony in only 13 days.

"To have a bird leave Brazil on 12 April and be home by the end of the month was just astounding. We always assumed they left some time in March," said Bridget Stutchbury, a biologist at York University in Toronto, Canada, who led the study.

The backpacks used technology developed by the British Antarctic Survey and were attached to the birds with thin straps around the legs. The weight lay at the base of the bird's spine so as not to disturb its balance.

Stutchbury said: "Never before has anyone been able to track songbirds for their migratory trip. We were flabbergasted by the birds' spring return times.

"Until now, our hands have been tied in many ways because we didn't know where the birds were going. They would just disappear and then come back in the spring. It's wonderful to now have a window into their journey."

The study, which is reported tomorrow in the journal Science, found prolonged stopovers are common during autumn migration. The purple martins spent up to a month in Mexico en route to their winter homes, for instance. It also showed that wood-thrushes from a single breeding population tend to spend the winter close together: all five tracked birds wintered in a narrow band in eastern Honduras or Nicaragua.

The research could also inform environmental concerns about songbirds, which have declined across the world over the past 30 or 40 years. "Tracking birds to their wintering areas is also essential for predicting the impact of tropical habitat loss and climate change," Stutchbury said.

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