Thermoregulation in the Brown Noddy ( Anous stolidus)

1. 1. Oxygen consumption ( V ̇ O 2 ), body temperature ( T b), respiratory frequency ( f) and total evaporative water loss were measured in Brown Noddies exposed to air temperatures ( T a) between −0.2 and 41.9°C, in a climatic chamber. 2. 2. The thermoneutral zone of T a was approx. 22–37°C and the V ̇ O 2 in the thermoneutral zone (1.031 ml/g h) was 77–80% of predicted values. 3. 3. The body temperature was characterized by its lability: even within the thermoneutral zone, there was a significant correlation with T a. 4. 4. Exposure to low T a resulted in shivering and a maximal increase in V ̇ O 2 of 129%. The minimal thermal conductance of the tissues and plumage below the lower critical T a was 86% of the predicted value. 5. 5. At high T a, thermal polypnea and open-beak panting were observed but the birds did not gular flutter. In some birds evaporative heat loss exceeded concurrent metabolic heat production. 6. 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.