ZIMMERMAN, B.B.*; TOBALSKE, B.W.: Effect of Flight Distance on Take-Off Mechanics in Zebra Finch

Flap-bounding is a flight style that is expected to offer an aerodynamic advantage over continuous flapping at fast flight speeds but not during hovering or slow flight. Therefore, we hypothesized that birds that exclusively flap-bound should maximize take-off velocity to avoid slow flight speeds, regardless of target flight distance. To test this prediction, we studied take-off in zebra finch (Taenopygia guttata, n = 6), a small flap-bounding species (14.8 g), as they flew distances from 2 to 10 m within a variable-length flight corridor. Horizontal and vertical ground reaction forces were obtained (5000 Hz) from a machined, instrumented, force perch, and synchronized high-speed video (1000 Hz) was used to measure wing and body kinematics. Generally consistent with our hypothesis, flight distance did not have a significant effect on the majority of the variables examined. However, as flight distance increased, horizontal velocity at the end of the jumping phase of take-off increased, and vertical velocity decreased. The percent contribution of leg thrust to horizontal velocity at the end of the jumping phase of takeoff also decreased significantly with an increase in target flight distance. Thus, the wings contributed proportionally more to take-off velocity as the target flight distance increased. Overall, average horizontal flight velocity at the end of take-off was 2.0 m/s. The minimum speed for which flap-bounding is predicted to be aerodynamically advantageous to a zebra finch is 6.0 m/s; clearly, a zebra finch must use additional wingbeats after take-off to reach this velocity. (supported by Murdock 99153)