Meeting Abstract

9.4  Thursday, Jan. 3  How do feathers produce aerodynamic sounds? Testing the ‘flag’ model CLARK, C. J.*; FEO, T. J.; UC Berkeley; UC Berkeley cclark@berkeley.edu

Birds produce a variety of sounds with their feathers. Many of these sounds are aerodynamic, generated by air flowing over individual or combinations of feathers. Although often called whistles, Clark and Feo (in review) suggested that Anna�s Hummingbirds’ tail-feathers do not whistle, and proposed a ‘flag’ model to explain how feathers produce sounds. The model makes several predictions. First, feathers flutter when producing sounds, rather than remaining static. Second, sound production only occurs above a set critical velocity. Third, above the critical velocity, the frequency (pitch) of the sound is set by the resonant frequency of the feather�s vane, and is insensitive to air velocity. Fourth, smaller feathers produce higher-pitched sounds. We test this model using rectrices (tail-feathers) of several species of Bee hummingbirds, which vary in size and shape, and appear to create a diversity of sounds during sexual displays.