Oxygen consumption, ventilation and respiratory heat loss in a parrot,Bolborhynchus lineola, in relation to ambient temperature

Abstract

1. Bolborhynchus lineola, a parrot of the humid tropics, has an unusually narrow thermoneutral zone (TNZ) (28–30 °C) and a total (wet) conductance 40% greater than predicted based upon its mass. 2. Within thermal neutrality mean tidal volume was 1.22 ml/breath and respiratory frequency was 28.6 breaths/min. These values are, respectively, 2.11 and 0.68 times allometrically predicted values (Lasiewski 1972). The mean rate of oxygen consumption in the TNZ during simultaneous measurement of other respiratory parameters was 1.87 ml O2/min and mean inspiratory minute volume equaled 34.3 ml/min (1.12 times the predicted value). 3. Mean oxygen extraction efficiency in the TNZ was 27.2%, 1.25 times the predicted value for a nonpasserine bird of 55.7 g and 1.66 times the predicted value for a similarly sized mammal. Maximum extraction efficiencies were about 53% at 27 °C and the highest mean value, 40.0%, was measured at that temperature. Mean oxygen extraction efficiency at allTa's belowTlc were higher than within TNZ or above it. 4. Total respiratory heat loss accounted for 9% of total heat production atTlc and only 3% of total heat production at 5 °C. Elevated oxygen extraction efficiencies belowTlc help to reduce respiratory heat loss. 5. Normal respiratory responses of resting birds to changes in ambient conditions can best be measured in totally unrestrained animals because respiratory frequency and oxygen consumption, and therefore oxygen extraction efficiency, are very labile and any disturbance masks normal responses.