Meeting Abstract

P3.80  Wednesday, Jan. 6  The Ontogeny of Lift and Drag Production in Birds HEERS, A.M.*; TOBALSKE, B.W.; DIAL, K.P.; University of Montana; University of Montana; University of Montana amheers@mac.com

Flight performance in developing birds may be limited by a number of factors, including muscular output, neuromuscular control, physiological processes, and/or wing morphology. In order to assess how external wing morphology – namely surface area, camber, and feather structure – influences lift and drag production during avian development, we prepared dried, spread wings of chukar (Alectoris chukar) in different age classes (day 6 through adult) and revolved the wings as a propeller. The propeller was mounted on a force plate, which allowed lift and drag to be measured. At natural angular velocities (recorded in vivo during 65° wing-assisted incline running, WAIR) and under identical flow conditions (same Re), coefficients of lift and drag and lift to drag ratios increased with age, revealing that external wing morphology limits aerodynamic performance in immature birds. While lift thus appears to play an increasingly important role in older birds, drag may be directed relatively vertically during WAIR and thereby contribute to weight support and propulsion, especially in younger birds. Given certain similarities between the wings of immature chukars and those of various fossilized theropods, these findings have profound implications for understanding the evolution of avian forelimb function and for extrapolating locomotor performance to extinct fossil forms. NSF Grants IOS 0923606 and IOS 0919799.