An amazing scientific discovery of how birds feed during mass migrations across continents

A team of American scientists recently made a surprising discovery about the surprising way migratory birds muster the energy to endure flights across continents.

With the help of a wind tunnel and a flock of birds, the team, led by scientists from the University of Massachusetts Amherst, was able to discover that migratory birds burn huge amounts of protein early in their flights. This turns the traditional theory on its head, which assumed that migratory birds increase their protein intake towards the end of their journeys.

Scientists also discovered that the birds, many of which make non-stop flights twice a year for more than 1,000 miles to get from their breeding range to their wintering range, fuel themselves by burning fat at a steady rate during their flights, and that they can burn a fifth of their muscle mass and rebuild again within a matter of time. days.

“Birds are amazing animals,” says Corey Eloy, lead author of the paper and a postdoctoral researcher in biology at the University of Massachusetts Amherst, where he earned his Ph. "From Canada to South America. How is that possible? How do they fuel their flight?"

For a very long time, biologists assumed that birds fueled such feats by burning fat reserves. Indeed, fat is an important part of the secretive mix of migratory birds. "The birds in our tests burned fat at a steady rate throughout their flights," says Eloy. "But we also found that they burn protein at a very high rate very early in their flights, and that the rate at which they burn protein diminishes as the duration of the flight increases."

"This is new insight," explains Alexander Gerson, associate professor of biology at the University of Massachusetts Amherst and senior author of the paper. "Nobody has been able to measure protein burn to this extent in birds before."

"We learned that birds burn protein, but not at this rate, and not so early in their flights. Moreover, these little songbirds can burn 20% of their muscle mass and then completely rebuild in a matter of days," Gerson continues.

To make the breakthrough, Eloy had help from bird range operators at Long Point Bird Observatory, in Ontario, along the north shore of Lake Erie.

Each fall, millions of birds congregate near the observatory on their journey to wintering grounds, including the blackpool warbler, a small songbird that travels thousands of miles on migration.

After capturing 20 blackpoll warblers and 44 yellow-rumped warblers, a species of songbird that migrates shorter distances, using fog nets, Eloy and his colleagues transported the birds to the Advanced Bird Research Facility at UCLA. Western, which has a specialized wind tunnel built specifically for observing birds in flight.

Eloy measured fat and lean body mass before the flight, then, when the sun went down, because the birds migrate at night, they left them in the wind tunnel.

 The scientists watched the birds to determine when they decided to rest. At that point, the team would collect the birds and again measure their body mass fat content and leanness, 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 chose 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 the birds can fly."

Scientists still don't quite know why birds burn up such vast stores of protein so early in their flights, but potential answers open up a wide range of future research avenues.