SEGRE, P.S.*; DIAL, K.P.; Univ. of Montana; Univ. of Montana: �Half a Wing� in Motion: the ontogeny and wing kinematics of WAIR in chukars

Before attaining full flight capabilities, most juvenile precocial birds proficiently negotiate their three-dimensional terrestrial environments in order to survive. These juveniles are in a dynamic transitional morphological state as they develop their musculature, plumage, and coordination. Although their wings are not yet capable of flight, their forelimbs produce significant aerodynamic forces just days after hatching. Using four, synchronized high-speed video cameras, we studied how developing chukar chicks employ wing-assisted incline running (WAIR: a recently described locomotor style involving simultaneous use of flapping wings and legs) in order to reach an elevated refuge and then return to lower ground using a controlled flapping descent. These distinctive locomotor tasks require an alteration of the wingbeat kinematics. We offer the first 3-D analysis of the ontogenetic development of wing movements (e.g., angle of attack, angle of incidence, stroke plane, and surface area) during WAIR and controlled descents. These data quantitatively illustrate the functional plasticity of wings during different locomotor tasks. The variance of wingbeat kinematics during ontogeny steadily decreases from day one until 20 days post-hatching, an age coincident with the ability to sustain forward flapping flight. The external wing morphology of these chicks share features with recently discovered theropod specimens with feathered forelimbs, suggesting living birds may provide insight into possible locomotor strategies and capabilities of feathered dinosaurs possessing �half a wing�. (Supported by NSF)