Meeting Abstract
Owls have silent flight, an adaptation for nocturnal hunting. One wing and feather structure thought to contribute to their ability to fly silently is a “velvety” dorsal surface on their flight feathers. This dorsal surface is derived from the elongated pennulae of feather barbules. How the velvet surface functions to reduce noise during flight is unclear. The aerodynamic noise hypothesis is that the elongated pennulae reduce aerodynamic noise caused by turbulence on the dorsal surface of the wing. By contrast, the structural noise hypothesis posits that the pennulae instead reduce noise produced by feathers sliding past one another during flight. We tested the structural noise hypothesis by measuring the sound produced by two feathers sliding past each other. According to the structural noise hypothesis, manipulating the pennulae (with hairspray) would result in an increase in structural sound produced, whereas manipulating feathers from other birds (that lack elongated pennulae) would have no such effect. Adjacent flight feathers were rubbed together at different speeds under three treatments: no treatment, hairspray, and hairspray removed. Our results have implications for ‘bio inspired’ silent flight.
