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Science 17 January 2003:
Vol. 299. no. 5605, pp. 402 - 404
DOI: 10.1126/science.1078237

Reports

Wing-Assisted Incline Running and the Evolution of Flight

Kenneth P. Dial

Flapping wings of galliform birds are routinely used to produce aerodynamic forces oriented toward the substrate to enhance hindlimb traction. Here, I document this behavior in natural and laboratory settings. Adult birds fully capable of aerial flight preferentially employ wing-assisted incline running (WAIR), rather than flying, to reach elevated refuges (such as cliffs, trees, and boulders). From the day of hatching and before attaining sustained aerial flight, developing ground birds use WAIR to enhance their locomotor performance through improved foot traction, ultimately permitting vertical running. WAIR provides insight from behaviors observable in living birds into the possible role of incipient wings in feathered theropod dinosaurs and offers a previously unstudied explanation for the evolution of avian flight.

Flight Laboratory, Avian Studies Program, Division of Biological Sciences, University of Montana (UM), Missoula, MT 59812, USA. E-mail: kdial{at}selway.umt.edu


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