70.3 Saturday, Jan. 5 The effect of elevation on hummingbird flight energetics: metabolic cost of flight in a changing environment GROOM, DJE*; TOLEDO, MCB; WELCH, KC; University of Toronto; Universidade de Taubate; University of Toronto email@example.com
Global climate change is projected to impact species diversity and range. In particular, many species will move to higher elevations in an effort to track their environmental niche. However, for all organisms, moving upwards poses its own set of challenges. This is strikingly problematic for flying animals, as flight becomes difficult at elevation due to changes in air density and oxygen availability. Previous studies have demonstrated that highland hummingbirds are generally larger and have larger wings relative to body size compared to lowlanders, which allows them to fly at lower air densities and temperatures. We seek to elucidate the metabolic cost of flight for hummingbirds at different elevations, and how aerobic capacity changes with elevation and size. We hypothesize that elevation, and consequently low oxygen availability, exerts a metabolic constraint on hovering flight by limiting maximal aerobic output. As a result, species found at higher elevations will have a comparable hovering metabolic rate to similarly sized lowlanders. However, the metabolic rate of highlanders will rise more rapidly under increasing power output challenges than lowland species. This would indicate that hummingbirds have a metabolic limitation to the elevation they can inhabit. Hummingbirds were captured at three sites (0m, 1000m, and 1800m asl) in the Atlantic Forest in the state of Sao Paulo, Brazil by mist netting. Metabolic rate was assessed during normal hovering flight and during sustained weight lifting. Weight lifting is used to increase the power requirements of flight, independent of oxygen availability. Information regarding metabolic capacity will allow us to understand the implications of elevation on energetic performance.