Time of feeding and possible associated thermoregulatory benefits in bronze mannikins Lonchura cucullata

Birds with a small body size have a high surface area to volume ratio, and this means that they have a high rate of heat loss to the environment. Birds may employ behavioural strategies in order to counter this heat loss. The adjustment of feeding patterns in the short term is probably the least documented of all of these strategies. Feeding results in the specific dynamic effect (SDE) which increases the metabolic rate of animals after a feeding bout. This increase in metabolic rate has been reported to possibly substitute for thermoregulatory costs in a variety of endotherms, including house wrens (Troglodytes aedon) and a variety of finch species. The thermoneutral zone was described for bronze mannikins, Lonchura cucullata (T(lc)=33.7 degrees C), and the bronze mannikins' post-absorptive physiology was described within this thermoneutral zone. Bronze mannikin mean basal metabolic rate (0.043+/-0.0038 S.E. ml O(2) min(-1) g(-1)), daytime resting metabolic rates (0.0549+/-0.0088 S.E. ml O(2) min(-1) g(-1)), and diurnal metabolic responses were described. The SDE in bronze mannikins was demonstrated within the thermoneutral zone, and was quantified. The mean magnitude of the SDE was 26.42% of mean total metabolism of post-absorptive birds. The magnitude of this SDE was independent of meal size and bird body mass. Assuming a 100% substitution, the presence of the SDE may afford bronze mannikins a maximum thermoregulatory energy saving of approximately 71.76 J g(-1) over a 300-min period.