ENERGY EXPENDITURE AND ITS COMPONENTS IN FREE-LIVING ARABIAN BABBLERS (TURDOIDES SQUAMICEPS)

Abstract

We determined the energy budget of the Arabian babbler (Turdoides squamiceps; Timaliidae), including the efficiency of energy use, using published data on resting metabolic rate (RMR), existence energy (EE), and field metabolic rate (FMR) of this desert passerine. Resting metabolic rate of the babblers was 0.65 kJ g^-1 d^-1 and EE was 1.10 kJ g^-1 d^-1. Therefore, RMR was approximately 59% of existence energy, and the efficiency of utilization of metabolizable energy for maintenance was 0.59. The heat increment of feeding (HIF) for maintenance for a diet of insects was 0.41, that is, 41% of the metabolizable energy consumed was used for food utilization. FMRs in summer and winter were similar and averaged 1.65 kJ g^-1 d^-1,breeding was 2.02 kJ g^-1 d^-1. The difference between either summer or winter FMR and EE in non-breeding babblers, 0.55 kJ g^-1 d^-1, was due to activity, mainly foraging, and may have included thermoregulatory costs in free-living birds. Breeding babblers required 0.37 kJ g^-1 d^-1 more than non-breeding birds; HIF for the increased energy intake was 19% of total energy expenditure. In general, energy expenditure of Arabian babblers was similar to that of other desert bird species but lower than that of non-desert species.