Torpor in an African caprimulgid, the freckled nightjar Caprimuigus tristigma

Recent data Suggest that facultative hypothermic responses such as torpor are more important in the energy balance of birds from tropical and sub-tropical regions than previously thought. We used telemetric measurements of skin temperature (T-skin) for five individuals on 151 bird-nights to investigate the occurrence of torpor during winter in an 81 g African caprimulgid, the freckled nightjar Caprimulgus tristigma. We found that freckled nightjars have the capacity to enter torpor, with a minimum observed T-skin of 12.8 degrees C. During the torpor bouts we observed, complete rewarming typically occurred after sunrise, and coincided with the availability of solar radiation. There was considerable inter-individual variability in the frequency and depth of torpor bouts, with one female nightjar exhibiting particularly frequent and deep torpor. Our results confirm the ability to use torpor by a nocturnal aerial insectivore from the Afrotropics, and reiterate the variability in patterns of torpor that can exist within a population.