Metabolic rate and body temperature of an African sun bird, Nectarinia chalybea: daily rhythm and the effect of ambient temperature

  • Belle Leon
  • Susan W Nicolson


The oxygen consumption (VO2) of the lesser double-collared sunbird, Nectarinia chalybea, was measured at ambient temperatures (Ta) from 7 to 35°C. The diel variation in body temperature (Tb) and wet thermal conductance (C) was also determined. The sunbirds (mean mass 8.36 g ± S.E. 0.21 g) showed a pronounced diel cycle of VO2 with a mean reduction of 50% at night. Basal metabolic rate was estimated to be 3.23 ml O2/g.h, which is 88% of the predicted value for a passerine bird of this size. There was a mean reduction in Tb of 3.6°C at night. Both day and night values of Tb decreased with decreaSing Ta, as did individual values of C. Winter breeding in the south-west Cape is energetically stressful for lesser double-collared sunbirds, but they have the physiological capacity to reduce their energy expenditure substantially at night.

S. Afr. J. Zool. 1997, 32(2)

Author Biographies

Belle Leon
Department of Physiology, University of Cape Town Medical School, Observatory, 7925 South Africa
Susan W Nicolson
Department of Zoology, University of Cape Town, Rondebosch, 7701 South Africa

eISSN: 2224-073X