THERMOREGULATION IN THE BROWN NODDY (ANOUS-STOLIDUS)

1. Oxygen consumption (V-O2), body temperature (T-b), respiratory freq uency (f) and total evaporative water loss were measured in Brown Nodd ies exposed to air temperatures (T-a) between -0.2 and 41.9 degrees C, in a climatic chamber. 2. The thermoneutral zone of T-a was approx. 2 2-37 degrees C and the V-O2, in the thermoneutral zone (1.031 ml/g h) was 77-80% of predicted values. 3. The body temperature was characteri zed by its lability: even within the thermoneutral zone, there was a s ignificant correlation with T-a. 4. Exposure to low T-a resulted in sh ivering and a maximal increase in V-O2 of 129%. The minimal thermal co nductance of the tissues and plumage below the lower critical T-a was 86% of the predicted value. 5. At high T-a, thermal polypnea and open- beak panting were observed but the birds did not gular flutter. In som e birds evaporative heat loss exceeded concurrent metabolic heat produ ction. 6. The features of thermoregulation in adult Brown Noddies are compared with those of the hatchling and also with thermoregulation in the related Sooty Tern.