LONDON, Feb. 15 (UPI) -- Tiny songbirds have been tracked in epic migrations as they travel 18,640 miles from sub-Saharan Africa to their arctic breeding grounds, researchers say.
Miniature tracking devices have revealed the impressive migration of the diminutive bird, known as the northern wheatear, which weighs 0.8 ounces, or 25 grams. Each tracking device weighs 1.4 grams.
"Scaled for body size," researchers report in the British Royal Society journal Biology Letters, "this is the one of the longest round-trip migratory journeys of any bird in the world."
Researchers tagged the wheatears in Alaska and Canada with the tracking devices that recorded the bird's position twice a day for 90 days.
Four trackers the researchers retrieved revealed that individual wheatears spent the winter in northern parts of sub-Saharan Africa.
"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," researcher Ryan Norris from the University of Guelph in Ontario, Canada, told the BBC.
The birds were tracked almost 9,000 miles each way, crossing Siberia and the Arabian Desert, and traveling an average of 180 miles a day.
"It seems that bird migration is limited [only] by the size of the Earth," research team member Heiko Schmaljohann, from the Institute of Avian Research in Wilhelmshaven, Germany, said.
"If the planet was larger, they would probably migrate even further."