Meeting Abstract

105.4  Wednesday, Jan. 7  Hummingbird courtship displays reveal limits to avian flight performance CLARK, CJ; UC Berkeley cclark@berkeley.edu

Courtship displays are a common feature of breeding behavior. While the information these displays convey between suitors and potential mate remains debated, the remarkable behaviors that result can be used to study the limits of locomotor performance. I provide an example of this paradigm based on the kinematics of the display dive of the Annas Hummingbird. I filmed diving male Annas Hummingbirds with a combination of high-speed and conventional video cameras. The dive consisted of five distinct stages based on stereotypical wing and tail kinematics. After powering the initial stage of their dive with flapping wings, males fold their wings and bound, at which point they reach an average maximum velocity of 27.3 m/s (385 body lengths /s). This suggests they have a body drag coefficient of less than 0.3. They then spread their wings to pull up, reaching centripetal accelerations of nearly 9 G, and concomitant torques. This acceleration appears to be higher than those attained by diving raptors, and may be limited by the torque the shoulder can withstand.