A group of American scientists recently made an amazing discovery about how migratory birds harvest energy in an amazing way to survive flights across continents.
Using a wind tunnel and a flock of birds, a team led by scientists from the University of Massachusetts Amherst was able to discover that migratory birds burn huge amounts of protein at the start of their flight. This turns on its head the traditional theory that migratory birds increase their protein intake towards the end of their journey.
The scientists also found that birds, many of which fly more than 1,000 miles non-stop twice a year to get from breeding grounds to wintering grounds, fuel themselves by burning fat at a constant rate as they fly. that they can burn off a fifth of their muscle mass and build it back up again in a matter of days.
“Birds are amazing animals,” says Corey Eloy, lead author of the paper and research fellow at the University of Massachusetts Amherst, where he completed his Ph.D. From Canada to South America. How is this possible? How do they fuel their flight?”
For a very long time, biologists assumed that birds fueled such feats by burning fat stores. Indeed, blubber is an important part of the secretive mix of migratory birds. “The birds in our tests burned fat at a constant rate throughout the flight,” says Eloy. “But we also found that they burned protein at a very high rate early in the flight, and that the rate at which they burned protein decreased.” . as the duration of the flight increases.
“This is a new insight,” explains Alexander Gerson, associate professor of biology at the University of Massachusetts Amherst and senior author of the paper. “Nobody has ever been able to measure this level of protein burning in birds before.”
“We learned that birds burn protein, but not as fast and not as early in the flight,” continues Gerson. “Moreover, these little songbirds can burn 20% of their muscle mass and then fully recover in a matter of days.” . “
To make the breakthrough, Eloy was aided by bird range operators from the Long Point Observatory in Ontario, located along the northern shore of Lake Erie.
Each autumn, millions of birds congregate near the observatory on their way to their wintering grounds, including the Blackpool warbler, a small songbird that migrates thousands of miles.
And after capture, 20 birds of the woodland warbler type (black warbler) and 44 birds of the yellow warbler (yellow warbler), a species of songbirds that migrate over shorter distances. Using fog nets, Eloy and his colleagues took the birds to Western University’s Center for Advanced Bird Research, which has a specialized wind tunnel built specifically for observing birds in flight.
Eloy measured lean and fat body mass before the flight, then when the sun went down as birds migrate at night, left them in the wind tunnel.
The scientists observed the birds to determine when they decided to rest. At this point, the team would collect the birds and measure their body weight, fat content, and leanness again, and compare the new data with their pre-flight measurements.
“One of the biggest surprises was that each bird still had a lot of fat when it decided to end its flight,” says Eloy. “But their muscles were lean. It appears that protein, not fat, is the limiting factor in determining how far birds can fly.”
Scientists still don’t fully understand why birds burn such huge stores of protein so early in flight, but potential answers open up a wide range of future avenues of research.
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