Metabolic rate and specific dynamic action of the Red-legged Honeycreeper, a nectar-feeding Neotropical passerine.

Rate of oxygen consumption (VO(2)) and carbon dioxide production (VCO(2)) were measured in the Red-legged Honeycreeper (Cyanerpes cyaneus, mean body mass 14.0+/-0.1g) at ambient temperatures (T(a)) between 15 degrees C and 35 degrees C to determine the basal metabolic rate (BMR). VO(2) in response to the light-dark cycle and the specific dynamic action (SDA) effect was also investigated. BMR was estimated to be 2.mLO(2) g(-1)h(-1), 10% lower than expected according to the Aschoff-Pohl relationship for passerines and 12% higher than expected following Mckechnie and Wolf's (2004) equation. Below 25 degrees C, VO(2) was linearly related to T(a). Body temperature averaged 40.2 degrees C and was not affected by T(a) over the range of temperature tested. The SDA was demonstrated at 20 degrees C by a two fold increase in VO(2) compared to pre-feeding levels. The honeycreepers showed a marked light-dark VO(2) cycle, with a mean reduction of 46% at night. During the night, birds rely on their body reserves as deduced from the respiratory quotient (RQ) values. Honeycreepers show a metabolic rate higher than predicted by allometry, marked diel fluctuations in their metabolic rates and a moderate SDA effect despite of the simplicity of nectar as food.