Meeting Abstract
Warming climates will likely cause organisms to adjust their energy budgets to accommodate temperature-related changes in direct (e.g. thermoregulatory) and indirect (e.g. foraging, flying) costs. Our goal is to determine which aspects of the daily energy budget (e.g. thermoregulation, daytime activity costs, nighttime costs) change in response to environmental variation. This will help us understand the strategies species might use to balance their energy budget over the short term to survive environmental extremes. Energy-budget management is particular challenging for hummingbirds because they have high metabolic rates and store little fat. The lack of significant energy storage by hummingbirds makes their energy budget relatively simple compared to other endothermic systems. We modeled energy budgets for two populations of broad-billed hummingbirds (Cynanthus latirostris) that vary significantly in their daily energy expenditure and live in habitats with different thermal profiles, topography, and vegetative structure. Our analyses show that the difference in daily energy expenditure was due primarily to thermoregulatory costs. High thermoregulatory costs appear to be balanced by a decrease in activity and concurrent use of more favorable microclimates. Decreased activity could reduce foraging and social interactions resulting in differential fitness across sites.
