Phenotypic flexibility in the basal metabolic rate of laughing doves: responses to short-term thermal acclimation.

Many birds exhibit considerable phenotypic flexibility in maintenance energy requirements, and up- or downregulate basal metabolic rate (BMR) over time scales of days to weeks during thermal acclimation. However, the extent to which individual birds can reverse the direction of BMR adjustments over short time scales remains unknown. In this study, we examined metabolic responses to short-term thermal acclimation in laughing doves Streptopelia senegalensis. In 30 wild-caught doves (mean body mass=92.6 g) divided into three experimental groups of 10 birds each, initial BMR averaged 0.760+/-0.036 W. Thereafter, each group was acclimated to one of three acclimation air temperatures (T(acc)=10, 22 or 35 degrees C) for 21 days, during which time the doves were housed in individual cages. Following the first acclimation period (acclimation I), BMR (W) was significantly lower and was negatively and linearly related to T(acc) [BMR=0.714-0.005T(acc)]. Acclimation I BMR varied from 0.546+/-0.039 W in doves acclimated to T(acc)=35 degrees C to 0.665+/-0.058 W at T(acc)=10 degrees C. A second acclimation period of a further 21 days (acclimation II) revealed that the direction of BMR adjustments could be reversed within individuals, with acclimation II BMR again negatively and linearly related to T(acc). The slope of the relationship between BMR and T(acc) following acclimation II was not significantly different to that following acclimation I. BMR exhibited consistent inter-individual variation, with a low but significant repeatability of 0.113. The within-individual BMR variation of up to 26% that we observed in laughing doves reveals that BMR is a highly flexible trait in this species, and reiterates the need to take phenotypic plasticity into account in comparative analyses of avian energetic parameters.