Meeting Abstract
Male hummingbirds produce loud sounds with their tail-feathers for females during a ‘dive display’ in which the male ascends then dives toward the female at high speed. As he performs this maneuver he spreads his tail feathers, which produce a loud tonal sound via aeroelastic flutter. The physical acoustics of this display is complex and depends both on the physical acoustics of feather flutter and on male behavior. We sought to understand how the male controls both the loudness and frequency of the sound he emits and of the sound the female receives. Wind tunnel experiments show that loudness depends on receiving angle (sound field is a directional, dipole-like, pattern), and that loudness and sound frequency depend on airspeed. Therefore, sound the female receives depends on elements of the male’s chosen trajectory: his speed, angle and distance from her as well as a Doppler shift in the sound. We tested a series of predictions about the sound field using an “acoustic camera”, which spatially maps sound sources onto visual frames.
