BREWER, Michael/L*; CHEVIRON, Zac/A; BRUMFIELD, Robb/T; ROBERTS, Stephen/P ; University of Nevada, Las Vegas; Louisiana State University; Louisiana State University; University of Nevada, Las Vegas: Altitudinal variation of wing shape in the Andean passerine Zonotrichia capensis

A challenge common to both engineered and biological volant forms is flight at high altitudes, where the density of air is low relative to that at sea level and thus compromises the lift capacity of airfoils. However, little is known about the role of high altitudes/hypodense atmospheres as selective forces shaping the morphology or aerodynamic properties of biological flyers. This research focuses on population-level variation in flight-related morphology of the passerine Zonotrichia capensis sampled over a relatively large altitudinal gradient along the Western Peruvian Andes. Collections were made at three elevational zones: low (0-1800 m), mid (2100-2400 m) and high (3000-4200 m). Body mass, wing loading, and aspect ratio did not differ significantly among the altitudinal groups. Low elevation birds had significantly shorter wingspans than either medium or high elevation birds. Thin-plate Spline/Relative Warp Analysis was used to compare wing planform shape independently of size. Relative warp 1 showed variation in the distal half of the wing and in the trailing edge at the wing base. High and low elevation birds were not significantly different from each other, yet mid elevation birds were significantly different than those from both high and low elevations. The leading edges of wings from mid elevation birds possessed greater aft sweep and a relatively less elliptical wing tip. Furthermore, wings from mid elevation birds showed an increased curvature at the transition of the trailing edge and the wing root. These findings suggest that, for this species, selective pressures on flight morphology maybe more strongly influenced by habitat type, and possibly predation risk, than by atmospheric pressure.