![]() ![]() The "stealthy hunting hypothesis" holds that owls fly inaudibly so that prey can’t hear them coming and have less time to escape. The sound-dampening structures didn't evolve by chance. Silent flight is clearly crucial for many owls' survival, and two long-held hypotheses attempt to explain this ability. These structures together streamline the air flow and absorb the sound produced. Those smaller streams of air are further dampened by a velvety texture unique to owl feathers and by a soft fringe on a wing's trailing edge. Comb-like serrations on the leading edge of wing feathers break up the turbulent air that typically creates a swooshing sound. Additionally, the structure of their feathers serves as a silencer. They have large wings relative to their body mass, which let them fly unusually slowly-as slowly as two mph for a large species like the Barn Owl-by gliding noiselessly with little flapping. “Owls have a suite of unique wing and feather features that enable them to reduce locomotion-induced sound,” says Krista Le Piane, a graduate student at the University of California, Riverside who recently presented her work on the evolution of silent owl flight at the Animal Behaviour Society conference in Ontario, Canada. Even large species like the Barn Owl or Great Horned Owl can fly virtually silently-a quality that has long fascinated scientists. When most birds fly, the air turbulence created by wing flapping produces sound, and, typically, the larger and faster a bird is, the noisier its flight. It won't be long before these downy juveniles grow into their adult feathers and gain the amazing ability shared by many owls around the world: to fly almost soundlessly through the trees. Each beat of their still-fuzzy wings whirred like a fan blade slicing the air as they slowly and awkwardly flapped up to a nearby tree branch. As we carefully approached, first one, then the other, flew noisily upwards. A few evenings ago, while walking through the forest at dusk, my daughter stopped us in our tracks with a loud "shush.” As we stopped to listen, she pointed towards a mewing sound on the trail just ahead of us-and there, two fledgling Barred Owls perched on a wooden railing. ![]()
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