Meeting Abstract
The wings of flapping fliers must be strong enough to resist the aerodynamic and inertial loads placed on them while also maintaining an aerodynamically appropriate shape for producing the requisite forces during flapping and gliding flight. The balance of these pressures differs among species with different flight styles and ecologies and wing morphology is expected to vary accordingly. In addition to 2D shape traits, such as aspect ratio, 3D attributes of wing morphology including camber and thickness may also vary significantly among species, and contribute to structural and aerodynamic function. North American raptors (Falconiformes) display a range of flight and hunting styles and vary in body mass by more than an order of magnitude, providing an opportunity to explore how wing morphology scales with body size, how it varies with flight behavior, and what constrains it. We collected 3D shape data from 200 individuals encompassing 19 raptor species, as well as two species of New World vultures (Coragyps atratus and Cathartes aura) using a laser scanner (NextEngine, Inc.) and analyzed 2D and 3D shape variables from the wing scans using custom programs in MATLAB and R. We hypothesized that if structural stiffness was the paramount pressure, wing thickness should be best predicted by bending load (proportional to mass*wing length). Conversely, if wing thickness is constrained by the aerodynamics of the wing, it should be best predicted by 2D attributes such as wing length and chord. We found that, in phylogenetically corrected and uncorrected models, wing thickness is better predicted by 2D attributes of wing shape (PGLS, r2=0.97, p<0.001) than by bending load (r2=0.66, ΔAIC=244.9, p<0.01) or body mass (r2=0.71, ΔAIC=173.4, p<0.01), suggesting that 3D wing shape, at least in the Falconiformes, is aerodynamically, rather than structurally constrained.
