Meeting Abstract
Many winged seeds autorotate and produce aerodynamic forces to effectively reduce their rate of descent. Isolated animal wings, however, have not yet been studied in this regard. We report that wings from Anna’s Hummingbirds and ten species of insects can spin around their center of mass and achieve descent speeds in a vertical wind tunnel similar to those reported for winged seeds. Sequential feather removal from hummingbird wings showed no effect on descent speed when the secondaries were removed, but substantially improved performance when only the last five primaries were present. Even wings with only the outer primary present showed stable autorotation, albeit with degraded performance. Manipulative experiments on hummingbird wings loaded at their base with approximately half of the bird’s body mass descended only twice as fast as the unloaded wings and rotated at frequencies similar than those exhibited by hovering hummingbirds. We show that whole dead insects can also autorotate depending on their fixed wing posture. Finally, we present a scaling law for aerodynamic performance during autorotation of animal wings.
