Owl Feathers – Mechanics of Silent Flight
Music; Ambience: Tattered rope swinging, Clean rope swinging
JM: The silent flight of an owl has captivated people for years. Now biologists are studying owl feathers in the hopes of learning more about their stealth ability. I’m Jim Metzner, and this is the Pulse of the Planet. Kim Middleton is a raptor biologist at the Peregrine Fund in Boise, Idaho.
KM: “The feathers on an owl all help contribute to allowing the bird to fly silently. The only hard surfaces on an owl that are not covered in feathers is the very tip of the beak and its talons. So that when an owl flies through the air there is no hard surface for the air to hit and the noise to be created”
JM: Owl feathers are unusual in having tattered edges, something like serrated knife blade.
KM: “This soft texture and tattered edges helps the feather to move through the air without creating a huge turbulent wake, which is what causes the sound to be created. This soft surface and the tattered edges breaks up that turbulence into many many many small turbulences, which kinda counteract each other.”
JM: Kim Middleton says you can observe this phenomenon by comparing the sounds made by swinging two pieces of rope – one that is frayed and one that is unfrayed.
KM: “Yeah, that’s the rope with the uniform woven surface. It has well defined edge. This rope has been unraveled part of the way and each individual fiber in the rope has been separated and it will create less sound.”
JM: Pulse of the Planet is presented with support provided by the National Science Foundation. I’m Jim Metzner.