Meeting Abstract
Studies of landing in birds have focused on perch landings involving short flights within a controlled laboratory. However, birds demonstrate the ability to land under a diverse set of conditions, including the ability to land on water, a fluid substrate. Landing on water enables birds to dissipate the energy of collision through skimming after impact. In this study, we examined the relationship between distance skimmed and impact speed, impact angle, and mean approach angle (the mean trajectory angle from a given landing). Landing mallards were recorded in the wild with a three-camera array (GoPro HERO4 Black) with 4k resolution at 30 fps. The array was calibrated with a 0.94 m wand and an audio synchronization through Argus 3D tracking software. Filming was conducted with wind speeds less than 3.3 m/s, in the months of October through May, 2017-2019. From 177 digitized landings, a diverse range of kinematics was documented, with impact speeds of 5.02 ± 1.36 m/s (mean ± SD) [range, 1.76 m/s, 8.48 m/s], impact angles of 14.8 ± 10° [0.6°, 59.9°], and mean approach angles of 8.6 ± 6.3° [-0.4°, 36.7°]. After impact, mallards skimmed a distance of 2.17 ± 1.36 m [0 m, 6.04 m]. Impact speed, impact angle, and mean approach angle are all significantly correlated to the distance skimmed after impact. However, a general linear regression model utilizing those kinematic features only accounts for approximately 25% of the variation seen in the distance skimmed, with impact speed accounting for the greatest portion (22%). This low value for the sum of the coefficients suggests much of the variation observed is the result of other factors including rotational movements of the body on impact, which may change the drag profile of the duck at the air-water interface.
