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First published online March 9, 2004
Journal of Experimental Biology 207, 1345-1352 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.00889

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Take-off mechanics in hummingbirds (Trochilidae)

Bret W. Tobalske^1,*, Douglas L. Altshuler² and Donald R. Powers³

¹ Department of Biology, University of Portland, 5000 North Willamette Boulevard, Portland, OR 97203, USA
² Bioengineering 138-78, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA
³ Biology Department, George Fox University, 414 N. Meridian Street, Newberg, OR 97132, USA

View larger version (49K): [in a new window]   Fig. 1. Kinematic events during an autonomous take-off in a male rufous hummingbird (Selasphorus rufus; body weight=30.7 mN). (A–F) Selected frames from 1000 Hzvideo illustrating body and wing posture; letters and timing (ms) for each frame correspond directly to those on the graph below. Vectors represent reaction forces produced by the hindlimbs on the perch; white scale bars, 10 mN. This sequence lasts 150 ms, and two wingbeats were completed prior to the end of take-off, defined as the start of the first downstroke after end of leg thrust.

View larger version (15K): [in a new window]   Fig. 2. Relative timing of kinematic events and peak ground-reaction forces during autonomous (N=6), escape (N=6) and aggressive (N=4) take-off in the rufous hummingbird (Selasphorus rufus) and autonomous take-off in the zebra finch (Taeniopygia guttata; N=1).

View larger version (22K): [in a new window]   Fig. 3. Selected kinematic and mechanical variables in the rufous hummingbird, Selasphorus rufus, as a function of take-off treatment. (A) Peak vertical and horizontal ground-reaction forces (N) and peak accelerations (m s–2). Vertical forces are net after subtracting g. (B) Velocity (m s–1) at the end of leg thrust and take-off. (C) Wingbeat frequency (Hz; inverse of wingbeat duration) during the first and second wingbeat in the take-off. N=6 hummingbirds for autonomous and escape and N=4 for aggressive; error bars represent ± S.D.

View larger version (15K): [in a new window]   Fig. 4. Scaling of velocity at end of take-off in 17 bird species including, in order of increasing body mass: rufous hummingbird (Selasphorus rufus); zebra finch (Taeniopygia guttata); dark-eyed junco (Junco hyemalis); house finch (Carpodacus mexicanus); diamond dove (Geopelia cuneata); American robin (Turdus migratorius); European starling (Sturnus vulgaris); western scrub jay (Aphelocoma californica); northern flicker (Colaptes auratus); ringed turtle-dove (Streptopelia risoria); European migratory quail (Coturnix coturnix); American crow (Corvus brachyrhynchos); rock dove (Columba livia); black oystercatcher (Haematopus bachmani); ring-necked pheasant (Phasianus colchicus); herring gull (Larus argentatus); wild turkey (Meleagris gallopavo). Regression lines from reduced-major axis regression of log-transformed data. (A) Species data, with open circle representing rufous hummingbird; y=0.25x–0.21, r=0.68. (B) Independent contrasts. Open circle represents contrast that includes rufous as daughter taxon; y=0.26x, r=0.65.