Meeting Abstract
The breadth of environmental conditions that species tolerate and exploit may, in large part, determine their geographic extent. Intuitively, species that can tolerate only a narrow set of environmental variables are expected to have smaller geographic distributions than species that thrive in more diverse conditions. Exploring how some species compensate for environmental challenges, and what prevents others from reacting similarly, may shed light on what determines their range. Turkey vultures (Cathartes aura) span a broad geographic range in North, Central and South America exposing them to a range of environmental conditions including elevations from sea level to >3000 meters. Because air density decreases with increased elevation, flight at high elevation presents a challenge for animals. Compensation for life in lower density air will manifest either in wing morphology, flight speed or increased power input. While some high elevation fliers have been shown to have larger wings, relative to their lowland relatives, and thus decreased wing loading (body mass/wing area), there has been less focus on whether and how fliers respond behaviorally. We used 3-dimensional videography to track the flights of turkey vultures at two elevations (~120 m and 2200 m) to look for evidence that high elevation vultures tend to fly faster than low elevation conspecifics. We predicted that the high elevation birds would have a 12% faster airspeed, on average, relative to low elevation birds, assuming that they are geometrically similar. Preliminary data analysis indicates that high elevation vultures fly approximately 7% faster, suggesting partial behavioral compensation for the elevational gradient. Our study exemplifies how field studies can illuminate the relationship between biomechanical performance and ecology.
