Design and performance of a rugged standard operative temperature thermometer for avian studies

The lack of a truly satisfactory sensor which can characterize the thermal environment at the spatial scale experienced by small endotherms has hinder ed study of their thermoregulatory behavior. We describe a general design f or a rugged, easily constructed sensor to measure standard operative temper ature, T-es. We present specific designs for adult dark-eyed juncos (Junco hyemalis) and hatchling mallards (Anas platyrhynchos). Sensor response was stable and repeatable (+/- 1.4%) over the course of several months. Over th e range of conditions for which validation data were available (variable ai r temperature and wind with negligible net radiation), sensors predicted th e mean net heat production of live animals to within +/- 0.023 W (equivalen t to +/-1 degreesC at T-es= 15 degreesC). The main limit on accuracy was sc atter in the data on metabolism and evaporative water loss in live animals. These sensors are far more rugged and easily constructed than the heated t axidermic mounts previously used to measure T-es. These characteristics fac ilitate the use of significant numbers of sensors in thermal mapping studie s of endotherms. (C) 2001 Elsevier Science Ltd. All rights reserved.