Might the hum of hummingbird wings also serve as a form of communication? It's unknown how well the birds can hear the sound of humming while in flight, but it's possible that this might play a role in how the birds interact with each other, Hightower said. – Why do birds sing the same song over and over?īut how does the hum of fast-moving wings sound to a hummingbird? In some species of hummingbirds, males generate high-pitched mating calls by vibrating their tail feathers, the study authors wrote. "A hummingbird wing is similar to a beautifully tuned instrument," Scholte said. This make the hum sound pleasant to humans - unlike the more irritating whine of a mosquito or the buzzing of a fly, according to Scholte. Variability in the way air moves over feathers and the wing's overall shape add overtones and nuance to the sound. At the speed that hummingbird wings move, these actions and air pressure differences during wingbeats account for the hummingbirds' humming sound. By comparison, hummingbird wings, which trace a "U" shape in the air as they flap, produce lift on both the downstroke and upstroke, the study authors found. In most flying birds, the "whoosh" that you hear is the sound of their downstroke - the only wingbeat to generate lift. "During the downstroke they're creating more lift, and then during the upstroke they're creating a little bit less lift," he said. Gravity is constantly pulling the hummingbirds down, but the force the birds generate from wing flaps to offset gravity's pull varies a little with every beat, Hightower explained. (Image credit: Sorama and Robert McMorran, USFWS) (opens in new tab)Īnother piece of the puzzle was the amount of aerodynamic force generated by the hummingbirds' wings during upstrokes and downstrokes, which the scientists measured using pressure plates, said lead study author Ben Hightower, a researcher who conducted these experiments when he was a doctoral candidate at Stanford's School of Engineering. High-speed cameras synched with microphone arrays to capture an acoustic "map" of the birds as they flew.
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