Meeting Abstract
Flight imposes numerous mechanical and evolutionary constraints on those animals that possess the ability; hence bird flight has been a focus of biomechanical studies for decades. 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. New open-source software, Argus, and the availability of ruggedized consumer grade cameras permit 3D reconstructions of movement of wild animals in natural settings. We used three GoPro Hero4 Black cameras to film (240 fps) wild Blue Jays (Cyanocitta cristata) approaching and departing a bird feeder 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. For example, one bird approached in a side-slip glide and relied on the last three wing beats to slow its velocity and reposition its body before landing. In this event, the second to last wing beat demonstrated an upward wing stroke plane angle of 7 degrees from horizontal, suggesting a reversed net thrust vector, and coinciding with the greatest deceleration in the approach. The naturally occurring behavioral variation among flight events provides not just a view into mechanics of flight in field conditions, but also the opportunity to examine the full variation of mechanical solutions to flight in the wild.
