How Do Barn Owls Fly So Silently?

The secret to an owl’s stealthy flight lies in the shape of its feathers.

With their striking eyes and swiveling heads, owls have long been a subject of fascination. They’re also forbidding predators. When hunting, owls swoop silently from the sky. To show just how impressive a feat this is, BBC Earth set up an experiment comparing owl flight to that of a pigeon and Peregrine Falcon.

Filmed with a slow-motion camera, the birds are shown swooping through a studio flight path outfitted with six hypersensitive microphones. The Barn Owl produces virtually no sound, while the pigeon (not surprisingly) and Peregrine Falcon (more so) register heavy flapping noise.

Owls are able to fly so silently for a combination of reasons, says Scott Weidensaul, an owl expert and contributing editor at Audubon. Owl feathers have a leading edge shaped like a comb and a trailing edge with a fringe; these funnel air smoothly over the wing and dampen the sound. An owl’s enormous wings, relative to its body size, also provide greater lift and enable it to fly slowly—as few as two miles per hour. “They’re buoyant in flight and moth-like,” Weidensaul says, further enhancing their ability to sneak up on small mammals. 

Peregrine Falcons, on the other hand, have evolved nearly the opposite flight strategy. Their wings are angled to be more aerodynamic, enabling them to dive at high speeds. Falcons make considerable noise as they fly up to 200 miles per hour, but that doesn’t matter since they’re faster than their prey.

Not all owls fly with the same ease as a Barn Owl. “The more nocturnal the owl, the more dependent it is on silent flight,” says Weidensaul. And that’s why the Barn Owl and Great Grey Owl are a particularly good model for engineers. In order to make wind turbines, computer fans, and airplanes more efficient, researchers have begun to model them after owls’ wings. 

Recently, for example, the University of Cambridge designed a coating to mimic the structure of an owl’s wing and tested it on turbine blade in a wind tunnel. The blade proved just as aerodynamic but notably quieter—not as silent as its avian inspiration, but a step in the right direction.