Friday, September 18, 2020

Flying high, flying straight – The Hindu

Flying high, flying straight - The Hindu

How long can Andean condor birds soar without flapping?

At 15 kg, Andean condors (Vultur gryphus) are the world’s heaviest soaring birds, with a wingspan of 10 feet. Condors spend 99% of all flight time in soaring/gliding flight. The ability to soar for hours with minimal flapping was seen in birds that were not adults. Documenting every single wingbeat of the birds, researchers have found that and Andean condors can sustain soaring for long hours without flapping their wings. Studying individual wingbeats for over 216 hours of flight, researchers found that they flap their wings for only 1% of their flight time. Even this flapping was specifically during take-off and when close to the ground; over 75% of flapping flight was associated with take-offs. Writing in the journal Proceedings of the National Academy of Sciences, a team led by E.L.C. Shepard from Swansea University, U.K., notes that one bird flew for over five hours without flapping, covering a distance of about 172 km. It is predicted that condors can soar long distances by flapping for about 2 seconds per kilometre. Since flapping imposes an economic cost, the overall flight effort of condors is constrained by the requirements for take-off. Even the wandering albatross (Diomedia exulans), which weighs about 9.4 kg and flaps minimally, spends 1.2-14.5% of its flight (outside take-off) in slow, flapping flight, they write. Currents of warm rising air and streams of air pushed upward by ground features such as mountains and wind gusts help these birds soar without flapping their wings. Ability to ride air currents allows them to travel long distances with minimal exertion.

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