Year of Award
Doctor of Philosophy (PhD)
Organismal Biology, Ecology, and Evolution
Department or School/College
Division of Biological Sciences
Bret W. Tobalske
Art Woods, Zac Cheviron, Stacey Combes, Bo Cheng
University of Montana
Birds morph their wings during a single wingbeat, across flight speeds, and among flight modes. Such morphing may allow them to maximize aerodynamic performance, but this assumption remains largely untested. We tested the aerodynamic performance of swept and extended wing postures of 13 raptor species in three families (Accipitridae, Falconidae, and Strigidae) using a propeller model to emulate mid-downstroke of flapping during takeoff and a wind tunnel to emulate gliding. Based on previous research, we hypothesized that 1) during flapping, wing posture would not affect maximum ratios of vertical and horizontal force coefficients (CV:CH), and that 2) extended wings would have higher maximum CV:CH when gliding. Contrary to each hypothesis, during flapping, extended wings had, on average, 31% higher max CV:CH ratios and 23% higher CV than swept wings across all biologically relevant attack angles (α), and, during gliding, max CV:CH ratios were similar for both postures. Swept wings had 11% higher CV than extended wings in gliding flight, suggesting flow conditions around these flexed raptor wings may be different from those in previous studies of swifts (Apodidae). Phylogenetic affiliation was a poor predictor of wing performance, due in part to high intrafamilial variation. Mass was only significantly correlated with extended wing performance during gliding. We conclude wing shape has a greater effect on force per unit wing area during flapping at low advance ratio, such as take-off, than during gliding.
Van Oorschot, Brett Klassen, "AERODYNAMICS AND ECOMORPHOLOGY OF FLEXIBLE FEATHERS AND MORPHING BIRD WINGS" (2017). Graduate Student Theses, Dissertations, & Professional Papers. 10962.
© Copyright 2017 Brett Klassen Van Oorschot