An eagle fitted with its own ‘black box’ flight recorder has revealed the soaring bird’s secret weapon against turbulence.

By rapidly collapsing its wings when encountering strong gusts of wind, the captive steppe eagle named Cossack was able to stay aloft in conditions that would have grounded fixed-wing aircraft.

Scientists believe other soarers including different eagle species, vultures and kites are likely to employ the same technique.

Cossack was sent on 45 experimental flights over the Brecon Beacons in Wales wearing a miniature rucksack packed with scientific instruments.

The 75g ‘black box’, which did not interfere with flying, both tracked his position with GPS and recorded measurements of acceleration, rotation rate and airspeed.

Scientists found that, faced with windy conditions, Cossack collapsed his wings in response to especially strong gusts instead of holding them out stiffly like a fixed-wing aircraft.

During each “wing tuck” his wings were – for a split second – folded beneath his body so that he was effectively falling. The wing tucks occurred up to three times a minute in some conditions.

Study leader Graham Taylor, from Oxford University’s Department of Zoology, said: “Soaring flight may appear effortless but it isn’t a free ride. Soaring may enable a bird to travel long distances but it also puts an enormous strain on its flight muscles.

“The nature of rising air masses, such as thermals, is that they create lots of turbulence and buffeting that jolts a bird’s wings and could knock it out of the sky.

“Our evidence suggests that wing-tucking is a direct response to a substantial loss of lift that occurs when a bird flies through a pocket of atmospheric turbulence.

“We think that, rather like the suspension on a car, birds use this technique to damp the potentially damaging jolting caused by turbulence.”

A number of theories have been put forward to explain why birds perform wing tucks, but none had been tested until now.

Prof. Taylor believes the lessons learned from Cossack could be useful to human aviation.

“While we won’t see large aircraft adopting collapsible wings, this kind of technique could potentially be used to keep micro air vehicles aloft even in very windy conditions,” he said.

The research is published in the Journal of the Royal Society Interface.

Sign up to our free newsletters

Get the best updates straight to your inbox:
Please select at least one mailing list.

You can unsubscribe at any time by clicking the link in the footer of our emails. We use Mailchimp as our marketing platform. By subscribing, you acknowledge that your information will be transferred to Mailchimp for processing.