ScienceTake | A Bird’s Secret to Soaring
Soaring birds have a special trick to beat air turbulence.
Video by Erica Berenstein on Publish Date October 20, 2014. Photo by Simon Walker/Oxford University.
When an aircraft hits turbulence, bad things can happen. At the very least, passengers may feel an unpleasant lurch in their stomachs.
But soaring birds, however they may feel, seem better able to deal with sudden gusts, said Graham K. Taylor, a mathematical biologist at the University of Oxford.
And the way they do it, he and his colleagues Kate V. Reynolds and Adrian L.R. Thomas have found, is by momentarily pulling in their wings — a maneuver called a wing tuck.
The behavior has long been observed in big soaring birds like eagles and vultures. But the three scientists recently reported in The Journal of the Royal Society Interface that they have documented the maneuver in “a level of detail that’s completely unprecedented” and shown that the tuck is different from regular wing flapping.
They collaborated on this work with a steppe eagle named Cossack, whom they have studied for about 10 years. Cossack wore an advanced recording device to track the details of his flight, like speed, turns and altitude.
Cossack flew 45 times for the experiment, during which the researchers recorded 2,594 wing tucks. They correlated the telemetry data with the video and with weather data.
As they expected, the wing tucks occurred in response to gusts. Each time, Cossack pulled in his wings and dropped into free fall for a moment, recovering quickly. There was no upstroke, so the move was not considered a flapping of the wings.
The researchers are careful with their conclusions because they studied only one bird. While they can’t conclude that the wing tuck evolved as a damping mechanism, like shock absorbers, that may be the case — and it certainly seems to be an inevitable result of having hinged wings. After a gust, when there is a sudden drop in the wind pushing up against the wings, Cossack, and presumably other birds like him, pull their wings in.
One exception might be albatrosses, which have a mechanism for locking their wings during soaring, which limits muscular effort. If he gets a chance, Dr. Taylor may look into the way albatrosses cope with turbulence.