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3-D kinematics of hummingbird flight


J Exp Biol. 2007 Jul 1;210(Pt 13):2368-82.

Three-dimensional kinematics of hummingbird flight.

Tobalske BW, Warrick DR, Clark CJ, Powers DR, Hedrick
TL, Hyder GA, Biewener AA.

Department of Biology, University of Portland, 5000 N.
Willamette Boulevard, Portland, OR 97203, USA.

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.