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First published online June 15, 2007
Journal of Experimental Biology 210, 2368-2382 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.005686
Three-dimensional kinematics of hummingbird flight
1 Department of Biology, University of Portland, 5000 N. Willamette
Boulevard, Portland, OR 97203, USA
2 Department of Zoology, Oregon State University, 2002 Cordley Hall,
Corvallis, OR 97331, USA
3 Department of Integrative Biology, University of California, Berkeley,
3060 Valley Life Sciences Building # 3140, Berkeley, CA 94720, USA
4 Biology Department, George Fox University, 414 N. Meridian Street,
Newberg, OR 97132, USA
5 Department of Biology, University of North Carolina, Chapel Hill, NC 27599
USA
6 Concord Field Station, Department of Organismic and Evolutionary Biology,
Harvard University, Old Causeway Road, Bedford, MA 01730, USA
* Author for correspondence (e-mail: tobalske{at}up.edu)
Accepted 24 April 2007
Hummingbirds are specialized for hovering flight, and substantial research has explored this behavior. Forward flight is also important to hummingbirds, but the manner in which they perform forward flight is not well documented. Previous research suggests that hummingbirds increase flight velocity by simultaneously tilting their body angle and stroke-plane angle of the wings, without varying wingbeat frequency and upstroke: downstroke span ratio. We hypothesized that other wing kinematics besides stroke-plane angle would vary in hummingbirds. To test this, we used synchronized high-speed (500 Hz) video cameras and measured the three-dimensional wing and body kinematics of rufous hummingbirds (Selasphorus rufus, 3 g, N=5) as they flew at velocities of 0-12 m s-1 in a wind tunnel. Consistent with earlier research, the angles of the body and the stroke plane changed with velocity, and the effect of velocity on wingbeat frequency was not significant. However, hummingbirds significantly altered other wing kinematics including chord angle, angle of attack, anatomical stroke-plane angle relative to their body, percent of wingbeat in downstroke, wingbeat amplitude, angular velocity of the wing, wingspan at mid-downstroke, and span ratio of the wingtips and wrists. This variation in bird-centered kinematics led to significant effects of flight velocity on the angle of attack of the wing and the area and angles of the global stroke planes during downstroke and upstroke. We provide new evidence that the paths of the wingtips and wrists change gradually but consistently with velocity, as in other bird species that possess pointed wings. Although hummingbirds flex their wings slightly at the wrist during upstroke, their average wingtip-span ratio of 93% revealed that they have kinematically `rigid' wings compared with other avian species.
Key words: Rufous hummingbird, Selasphorus rufus, kinematics, flight
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