CLARK, Christopher J.; TOBALSKE, Bret; POWERS, Don; Univ. of California, Berkeley; University of Portland; John Fox University: Forward flight kinematics of rufus hummingbirds (Selasphorus rufus) with and without their tails

Birds use their tails to generate aerodynamic forces. Recent theoretical work has begun to identify potential uses of these forces. In forward flight, there are two possible uses of these aerodynamic forces: 1) supplemental lift production during slow flight, and 2) transient, stabilizing forces to control body position. However, the relative importance of these uses to flying birds has not been tested empirically. Because hummingbirds are capable of hovering without their tail, we predict that hummingbirds do not use their tails to produce additional lift in forward flight. We also predict that absence of the tail decreases stability, particularly at higher speeds. We tested these hypotheses by filming the kinematics of four wild, female rufus hummingbirds (Selasphorus rufus). We filmed the birds flying in a wind tunnel at 0, 2, 4, 6, 8, 10, and 12 m/s using three synched high-speed cameras, two filming at 500 fps and one at 250 fps. Each bird was filmed flying with its entire tail, with the proximal half of its tail, and with no tail. We present the differences in forward flight kinematics of rufus hummingbirds before and after manipulations. This work was supported by Murdock grant 2001208.