25g birds tracked on epic migrations
Miniature tracking devices have revealed the epic 30,000km migration of the diminutive northern wheatear.
The birds, which weigh just 25g, travel from sub-Saharan Africa to their Arctic breeding grounds, BBC Nature reported Wednesday.
"Scaled for body size," the scientists report, "this is the one of the longest round-trip migratory journeys of any bird in the world.
The team reports its findings in the Royal Society journal Biology Letters.
"Think of something smaller than an [American] robin, but a little larger than a finch raising young in the Arctic tundra and then a few months later foraging for food in Africa for the winter," said one of the lead researchers, Prof Ryan Norris from the University of Guelph in Ontario, Canada.
The species is of particular interest to scientists, because it has one of the largest ranges of any songbird in the world; with breeding grounds in the eastern Canadian Arctic, across Greenland, Eurasia and into Alaska.
Prior to this work though, it was not clear where the birds spent the winter.
Heiko Schmaljohann, from the Institute of Avian Research in Wilhelmshaven, Germany, was a member of the team that carried out this study.
He and his colleagues visited the wheatears' breeding grounds in Alaska and Canada and fitted 46 birds with the satellite tracking devices.
"The [trackers] weigh 1.4g, including a harness that loops around the birds' legs," he told BBC Nature.
These data loggers recorded the bird's position twice a day for 90 days. Four trackers that the team managed to retrieve revealed that individual wheatears spent the winter in northern parts of sub-Saharan Africa.
The Alaskan birds travelled almost 15,000km (9,000 miles) each way - crossing Siberia and the Arabian Desert, and travelling, on average, 290km per day.
"This is the longest recorded migration for a songbird as far as we know," said Dr Schmaljohann.
Although the Canadian birds did not travel as far - approximately 3,500km - they had to cross the northern Atlantic Ocean.
"That's a very big barrier for a small songbird," Dr Schmaljohann explained.