Oxygen consumption, evaporative water loss and body temperature in the Sooty Tern, Sterna fuscata

Abstract

Reports were scanned in black and white at a resolution of 600 dots per inch and were converted to text using Adobe Paper Capture Plug-in.1.The oxygen consumption, total evaporative water loss, and deep-body temperature of Sooty Terns were measured at air temperatures within the range 10°C - 45°C. 2. At air temperatures from 10°C to 30°C, the cloacal temperatures were relatively constant, the temperature of the fledglings tending to exceed that of the adults. At air temperatures of 35°C and higher, the birds became hyperthermic. 3. The thennoneutral temperature was approximately 30°C. The heat production of the terns was lower than the predicted value for non-passerine birds of their weight. 4 . Thermal polynea was observed at the higher air temperatures, but at an air temperature of 44°C - 45°C, only one bird was able to dissipate heat in excess of heat production, by evaporative cooling. 5. The calculated thermal conductance was constant at air temperatures of 10-30°C, but the conductance increased at higher temperatures. 6. It was concluded that Sooty Terns are not especially proficient at evaporative cooling, in spite of the thermal demands of their tropical environment. They appear to rely also on a rather low level of heat production, air movement and behavioral mechanisms of temperature regulation.Supported by NSF Grant GB-23230 and GB 29287X Island Ecosystems IRP/IBP Hawaii, and from the Primo Foundatio