Meeting Abstract
P3.74 Monday, Jan. 6 15:30 Using an endotherm energetic model to predict hovering metabolic rates of hummingbirds POWERS, SD*; POWERS, DR; TOBALSKE, BW; WETHINGTON, SM; George Fox Univ, Newberg, OR; George Fox Univ, Newberg, OR; Univ. of Montana, Missoula, MT; Hummingbird Monitoring Network, Patagonia, AZ seandpowers@gmail.com
Hummingbirds provide a unique opportunity to understand the response of small endotherms to climate change. They inhabit a broad range of ecosystems and because of their small size operate at the limits of endothermic physiology (i.e. energy expenditure is carefully managed). Increased thermoregulatory costs and changes in energy resources likely tied to climate change might profoundly impact daily energy expenditure. Since hummingbirds are key pollinators in many important ecosystems understanding the impact of climate change on metabolic costs is crucial. Our goal was to model heat generation in hovering hummingbirds in order to predict hovering metabolic rate (HMR) over a range of environmental temperatures (endotherm model; Porter et al., 1994; Porter and Kearny, 2009). To model HMRs we used infrared thermography (IRT) to measure surface body temperatures. From these IRT measurements we calculated the HMR needed to maintain core body temperatures of hummingbirds during hovering. To validate the model we did a sensitivity analysis using linear regression with observed HMR. We found that the relationship between predicted and observed values was not significant (F = 0.002, p = 0.997). The slope of this relationship (m = 0.425) also indicated the endothermic model was not in agreement with the observed values. Our results demonstrate two problems. First is how the extra heat generated by the flight muscles contributes to the determination of surface body temperatures. Second is the integration of IRT measurements with the endotherm model. To do this we need to better understand the role plumage plays in heat dissipation. We plan further experiments to explore these issues.
