Meeting Abstract

P3-142   -   Air temperature effects on the physiology of work in mid-elevation tropical birds Oliver, KD*; Martin, TE; Wolf, BO; University of New Mexico, Albuquerque, NM; University of Montana, USGS Montana Cooperative Wildlife Research Unit, Missoula, MT; University of New Mexico, Albuquerque, NM kristenoliver@unm.edu http://kristenoliver.org

The effect of temperature on breeding birds is of increasing interest as global air temperatures continue to rise. According to the heat dissipation limit theory, birds and many other endotherms may face limits to activities in a warming climate. If activities such as foraging and feeding nestlings decrease due to limits on heat dissipation, then reproductive success may also decline. We are interested in understanding how increasing air temperature affects sustainable workloads and do these affects vary with species, and body size. With these questions in mind, we surveyed a tropical mid-elevation (1500-1900m) community of birds in Mount Kinabalu National Park in Borneo, Malaysia where air temperatures range from 15-21°C. We used flow-through respirometry to measure resting metabolic rate, basal metabolic rates, evaporative water loss, and body temperature in 12 species of birds. We also used a hop-flutter wheel to measure exercise metabolic rates. We took measurements in species across a range of body sizes (6g -140g) at air temperatures ranging from 16°C - 30°C. We found that regulation of body temperature, evaporative water loss, dry heat loss and metabolic rate vary with body size and air temperature during work. Larger species show increased dependence on their ability to evaporatively cool with increasing air temperature. Smaller species demonstrate similar trends but exhibit higher body temperatures than large species and depend on evaporative cooling at the highest air temperatures. These data suggest that heat dissipation may limit workloads at higher air temperatures in some species. The 30g Mountain Wren-babbler (Napothera crassa), for example, reached lethal limits during workloads at 30°C.