Specialized feathers of the owl enable near-silent flight by altering air turbulence and absorbing noise.

Introduction

Owls are known as silent predators of the night, capable of flying just inches from their prey without being detected. The quietness of their flight is owed to their specialized feathers. When air rushes over an ordinary wing, it typically creates a “gushing” noise as large areas of air turbulence build up. But the owl has a few ways to alter this turbulence and reduce its noise.

The Strategy

First, the leading edge of the owl’s wing has feathers covered in small structures that project out from the wing. One hypothesis is that these serrations break up the flowing air into smaller flows that are more stable along the wing. Furthermore, this change in airflow patterns also appears to reduce the noise of the flowing air. The wing’s serrated leading edge appears to be most effective at reducing noise when the wing is at a steep angle—which would happen when the owl is close to its prey and coming in for a strike.

Detail view of the stiff curved serrations on the leading edge of an owl wing feather
Image: Radd Icenoggle / Copyright © - All rights reserved

A close view of the leading edge of an owl's outer wing feather shows the stiff serrations that help create a smooth flow of air above the wing. Photo © Radd Icenoggle, used with permission.

detail of feathers on an owl wing showing the leading and trailing edges
Image: Radd Icenoggle / Copyright © - All rights reserved

While stiff serrations break up air flow on the leading edge of owl wing feathers, softer serrations on the trailing edge (upper left) help to tame turbulence in the feathers' wake. Photo © Radd Icenoggle, used with permission.

These smaller airflows then roll along the owl’s wing toward the trailing edge, which is comprised of a fine fringe. This fringe breaks up the air further as it flows off the trailing edge, resulting in a large reduction in aerodynamic noise. Then, any remaining noise that would be detectable by the owl’s prey is absorbed by velvety down feathers on the owl’s wings and legs. These soft feathers absorb high frequency sounds that most prey, as well as humans, are sensitive to. All together, these feather features enable owls to remain unheard when they fly.

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The Potential

Aspects of owl feather aerodynamics have already been employed in wind turbines and the Shinkansen train aerofoil. They could similarly improve efficiency and minimize noise for the wings of airplanes and the blades of helicopters and drones. Fan blades for home and industrial use could also make use of these strategies.

Owl feather strategies could also be used to create different aerodynamic effects for fabric-based wings, such as kites, parachutes, gliders, banners and more.

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Last Updated September 21, 2019