Thermoregulatory physiology of the Crested Pigeon Ocyphaps lophotes and the Brush Bronzewing Phaps elegans

The metabolic physiology of the Crested Pigeon (Ocyphaps lophotes) and the Brush Bronzewing (Phaps elegans) is generally similar to that expected for birds of their size, but the Crested Pigeon has a number of characteristics which would aid survival in hot and dry regions. Body temperature increased similarly for the Crested Pigeon (from 38.8 °C to 41.5 °C) and the Brush Bronzewing (39.3 °C to 41.4 °C) over ambient temperatures (Tas) from 10 °C to 35 °C. Both species became hyperthermic (body temperature, Tb>42 °C) at Ta=45 °C. Basal metabolic rate of the Crested Pigeon (0.65 ml O2 g-1 h-1 at 40 °C) was ~71% of that predicted for a columbid bird, while BMR of the Brush Bronzewing (0.87 ml O2 g-1 h-1 at 20 °C to 40 °C) was ~102% of predicted. Total evaporative water loss increased exponentially with Ta for both species, from 12 mg H2O g-1 h-1 at 45 °C. It was similar and low for both species at Ta30 °C. Ventilatory minute volume matched oxygen consumption, such that oxygen extraction efficiency did not change with Ta and was similar for both species (~20%). Expired air temperature was considerably lower than Tb for both species at Ta