Was It Designed?

The Owl’s Feather

◼Flight engineers look with envy upon the nocturnal owl. Why? Because of its silent flight. “No other birds fly with such stealth,” says the National Geographic Web site. What is the owl’s secret?

Consider: The air that rushes over the feathers of most birds creates a turbulence that can be quite noisy. With the owl, on the other hand, it is different. Its trailing feathers have fringes that break up the sound waves that are generated as air flows over the top of the wing at the downstroke. The downy feathers found elsewhere on the owl’s body help absorb the remaining sound.

Aircraft designers would like to tap into the secret of the owl’s virtually silent flight. Quieter planes would mean that airports with stringent noise limits could allow flights to take off and land at later hours of the night​—and earlier hours of the morning. Some improvements are already being planned. “We are just now coming along,” says Geoffrey Lilley, professor emeritus of aeronautics at England’s University of Southampton. He adds that it could be decades before such a quiet plane could be designed.

What do you think? Was the owl’s noise-reducing trailing feather a product of chance? Or was it designed?

[Picture on page 23]

Compare an owl’s feather on the left with a hawk’s on the right

[Picture Credit Lines on page 23]

Long-eared owl: © Joe McDonald/​Visuals Unlimited; barn owl sequence: © Andy Harmer/​Photo Researchers, Inc.; feather comparison: Courtesy of Eike Wulfmeyer/​Wikimedia/​GFDL