J027041 Cyclic variation in wing-morphing of a hovering hummingbird

Hummingbirds are the only species in birds capable of performing continuous hovering flight. However, the precise aerodynamic force generating mechanisms, which should be associated with the dynamic wing-morphing, still remains unclear. In this study, targeting at hummingbird Amazilia amazilia, we aim at conducting a systematic analysis of flapping-wing kinematics and dynamic configuration of the wings during hovering flight. With use of a filming system consisting of four synchronized digital high-speed video cameras operating at 2000 frames per second, we recorded a sequence of hovering with sufficiently high resolution. With the video images, characteristic points on the right wing of the hummingbird were tracked. Additionally, we conducted the flapping experiment to evaluate the effect of the wing-morphing on lift generation. Two time-variant wing deformation parameters were obtained: wing surface area and spanwise twist. We found that the wing area shows a variation up to 20% within a wingbeat cycle. Our results indicate that the time variation of the angles between adjacent primary feather shafts is the main cause of the variation of the wing area. The wing twist shows asymmetric variation during upstroke and downstroke, and this asymmetry is prominent for the inboard part of the wing. The hummingbird-inspired flapper experiment shows it is generating sufficient aerodynamic force to support the original hummingbirds weight based on which it is modeled.