Meeting Abstract
Flight imposes numerous mechanical and evolutionary constraints on those animals that possess the ability, which may also imply kinematic constraints. Most of our understanding derives from laboratory studies, often of birds in wind-tunnels performing steady flight, or in other artificial scenarios. However, flight evolved and is routinely performed in wild and variable settings where successful take-offs and landings are critical, and variation in kinematics may be expected. We used three GoPro Hero4 Black cameras to film (240 fps) wild Blue Jays (Cyanocitta cristata) approaching and departing bird feeders in Farmville, VA, U.S.A. After calibrating the three-dimensional volume with a wand of known length, correcting for lens distortion, and synchronizing the videos using the audio tracks, we were able to reconstruct the 3D positions of ten points on the birds’ bodies and wings within the filming volume (~ 1 x 1 x 3 m). We calculated several kinematic factors, which varied among flights, but from which basic mechanical hypotheses can be examined. Consistently performed rapid pitch-up maneuvers have been linked to energy dissipation in past controlled experiments. However, our field observations on just 5 flights show extensive variation in angle of attack and stroke plane angles used while landing. For example, the wing stroke plane angle during the last wing beat prior to landing ranged from positive 7 degrees (upward) to negative 40 degree (downward). This variation suggests that even within a species there are multiple kinematic solutions to the mechanical problem of landing, and the optimal solution likely depends on variation in approaching speeds and angles (outside of our filming volume), behavioral input, or regular variation between individuals of the same species.
