Meeting Abstract
Vertical flight is particularly challenging for birds, bats, and insects because of simultaneous and large increases in the costs to overcome gravity and drag, particularly at high speeds of ascent. We analyzed vertical flight performance for four male Anna’s Hummingbirds (Calypte anna) ascending over a 2 meter distance. Birds flew using a horizontal stroke plane and a vertical body axis, reaching stroke amplitudes as high as 190o. Mass-specific aerodynamic power at maximal climbing speed was about 60 W/kg, a value similar to that obtained in earlier maximal load-lifting studies. Near the top of the flight trajectory, birds stopped flapping and folded their wings against the body to effect a smooth deceleration towards a feeder. The first derivative of the tau function (i.e., the visual distance to target divided by the instantaneous velocity), averaged 0.75, in accordance with previous studies of hummingbirds during horizontal deceleration towards flowers. We conclude that hummingbirds transiently reach maximal aerodynamic performance during vertical ascent, but can then precisely decelerate, without flapping, using visual cues to effect a controlled braking within 170 ms.
