A team of scientists led by researchers from the University of Massachusetts Amherst (USA) It was solved recently with the help of a wind tunnel and a flock of birds. migratory birds their strength for such long uninterrupted journeys.. Flying several thousand kilometers twice a year from breeding ground to wintering ground, these birds work by burning a staggering amount of protein and a lot of fat that build their body mass, including muscle. early stages of flight.
This subverts the generally accepted belief. He hypothesized that migratory birds only increase their protein consumption at the end of their journey.because they’ll have to use every ounce of their muscle to flap their wings, not to burn fat.
“Birds are wonderful animals,” says Cory Elowe, lead author of the paper and a postdoctoral researcher in biology at UMass Amherst. “They are extreme endurance athletes; A bird weighing 15 grams can fly 100 hours nonstop from Canada to South America. How can they withstand such a long journey?”
Burning proteins from the start of flight
For a long time, biologists assumed that birds perform such skills by burning their fat stores. And indeed, oil is an essential part of the secret formula of migratory birds. “The birds we studied in our tests burned fat at a constant rate throughout their flight,” says Elowe. “But also We found that they burned a fairly high percentage of protein early in their flight.and the longer the flight time, the lower the protein burning rate,” he added.
“This is a new perspective on the subject,” says Alexander Gerson, associate professor of biology at UMass Amherst and lead author of the paper. “No one has ever measured how protein is burned before” in such migratory flights of birds.
“We knew that birds burn protein, but not at this speed and this early in their flight.” Gerson continues. “Also, these little birds can burn up to 20% of their muscle mass and regain it in a matter of days.”
To make this breakthrough, Elowe enlisted the help of bird groupers from the Long Point Bird Observatory in Ontario, along the northern shore of Lake Erie. Every autumn, millions of birds gather near this observatory on their journey to their wintering grounds, including the black warbler, a small songbird that travels thousands of kilometers on its migration.
Using a wind tunnel
After capturing 20 striped warblers and 44 crowned warblers, a shorter-range migratory bird, Elowe and colleagues transported these animals to Earth. Advanced Bird Research Center at Western University, which has a dedicated wind tunnel It was specially built to watch flying birds.
Elowe measured the birds’ fat and lean body mass before flight, and then dropped them into the wind tunnel as the sun went down. Because birds naturally migrate at night, Elowe and his colleagues stayed awake for 28 hours, observing when a bird would decide to rest. At this point, the researchers would take the bird and measure the fat and lean body mass content again, comparing the data with the pre-flight measurements.
“One of the biggest surprises was that when each bird decided to end its flight, there was still a lot of oil left.”says Elowe. “But their muscles had weakened. It seems like protein, not fat, is the limiting factor in how far birds can fly.”
Researchers still don’t know exactly why birds deplete such large stores of protein so early in their journey.however, it opens up a wide range of possible answers for future research avenues.
“How is it possible to burn your muscles and internal organs and then rebuild them as quickly as these birds,” Gerson said. she wonders. “What insights can these birds produce about the evolution of metabolism?”
Elowe wonders about shivering: Non-migratory birds that spend the winter in cold regions warm up by shivering. “It’s also an endurance achievement,” says Elowe. “Do birds feed on the winter cold the same way? And as the world warms, what method of dealing with the cold, shivering or migrating might be the best option for survival?” she wonders.
Reference work: https://www.pnas.org/doi/10.1073/pnas.2216016120
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