Meeting Abstract

102.2  Tuesday, Jan. 7 08:15  Thermal Physiology, Climate, and Altitude Zonation in Andean Birds CHAPPELL, M.A.*; LONGONO, G.A.; JANKOWSKI, J.E.; ROBINSON, S.K.; Univ. of California, Riverside; Univ. of California, Riverside; Univ. of British Columbia, Vancouver; Univ. of Florida, Gainesville chappell@ucr.edu

Tropical bird communities along the eastern slope of the Andes are characterized by striking altitude limits on species distributions. Over habitats ranging from hot, humid lowland forest up to cool highland cloud forest and alpine grasslands, numerous bird species are restricted to narrow altitude ranges, often encompassing 1000 m or less. Range limits may result from abiotic or biotic factors, or a combination of the two. We used measurements of thermal physiology and weather data to explore the possible role of an important abiotic factor, ambient temperature, in determining altitude limits for a sample of about 200 bird species from southeastern Peru. We used data from respirometry to test if thermal conductance and body temperature differed across altitudes (400 – 3000 m). Birds (3- 300 g) were mist-netted and measured at night under conditions appropriate for eliciting minimal thermal conductance (ambient temperature 10 °C, body temperature > 35 °C). Both thermal conductance and body temperature decreased as altitude increased. We combined these results with weather data to estimate the energy costs of thermoregulation across altitudes. Thermoregulatory costs were compared to basal metabolic rate (BMR) to see if they exceeded several potential limits that might prevent species from occupying particular altitudes. We found little indication that thermal constraints could account for altitude range limits in our sample of Peruvian birds.