Meeting Abstract
Higher temperatures associated with climate change in landscapes used by hummingbirds might increase thermoregulatory costs and alter foraging patterns resulting in increased daily energy expenditure (DEE). Because hummingbirds are key pollinators, changes in behavior or distribution could alter ecosystem dynamics. One response might be to move to higher elevation where reduced daytime temperature would allow better control of thermoregulatory costs. Moving to higher elevation might not be an energy-neutral transition as ecosystem shifts such as change in resource type/distribution, cooler nighttime temperature, decreased air density, and new competitive interactions could result in higher DEE. In this study we measured DEE in hummingbirds at different elevations as a first step in understanding energetic costs associated with high-elevation ecosystems. To do this we used doubly labeled water (DLW) to measure DEE in hummingbirds at two sites along an elevational gradient on the west slope of Andes Mts. in Ecuador. We studied 2 hummingbird species (mass 7-8.7g) at our low-elevation site (~1300m, LE) and 1 species (9.40-9.70g) at higher elevation (~1900m, HE). Mean CO2 production was 17.4-20.5 mL CO2 g-1h-1 at LE, and 21.7-24.6 mL CO2 g-1h-1 at HE. HE DEE was ~6-30% higher depending on species compared. DLW does not segregate energy costs, but many factors could promote higher DEE at HE. Also, torpor is used more frequently at LE, which might make the difference in DEE smaller. Potential taxonomic differences between species also cannot be ignored.
