Meeting Abstract

126.1  Tuesday, Jan. 7 13:30  Extending the U: Power estimates of Cliff Swallow low-speed flight and hovering in the field JACKSON, BE*; HEDRICK, TL; Skidmore College; Univ. North Carolina, Chapel Hill bjackson@skidmore.edu

Most of our understanding of animal locomotion biomechanics comes from examining a limited set of behaviors in laboratory settings. For example, the costs and mechanisms of bird flight have been described from wind-tunnel studies and indicate a U-shaped curve for flight power versus speed. However, most experimental or theoretical curves treat low speed flight (< ca. 3 ms^-1) as a black box, either because our understanding of wing function at low speeds is limited, or because most birds refuse to fly at low speeds in laboratory settings. We recorded Cliff Swallows (Petrochelidon pyrrhonota) in the field approaching, departing, and hovering near nests with three synchronized high-speed cameras, and used a new structure-from-motion rapid camera calibration technique designed for the field to measure three-dimensional kinematics of the birds’ bodies and wings. Our kinematics-based analysis indicates that the power required for such flight is substantially higher than published power curves at more moderate flight speeds, but well within the likely capacity of the flight muscles. The birds met the high power requirements with geometrically maximal stroke amplitudes, high wingbeat frequencies, high angles of attack, and increased lift coefficients compared to cruising flight speeds. However, power was statistically invariant across these low speeds (0-3 ms^-1). This suggests that the left edge of the U-shaped power curve, at least in cliff swallows, may be a dramatically high plateau rather than a smooth continuation of the U. Such findings, along with our other quantitative field investigations of swallow flight behavior provide substantial new insight into the biomechanics of avian flight. Supported by Office of Naval Research MURI (ONR N000141010952).