The Cooling Power Of Pigeon Legs

The rate of heat loss from legs and feet (ḢLEG) was studied in resting pigeons preheated to a body temperature (43·1 °C) close to those recorded during flight. The experimental system was designed to allow the calculation of ḢLEG from whole-body cooling rates following exposure of the legs and feet to various combinations of wind speed (0–75 km h−1) and air temperature (5–25°C). The pigeons remained hyperthermic when their hindlimbs were kept insulated, but their bodies cooled markedly as a result of exposure of the legs and feet. With a 12·5kmh−1 wind at 25°C, ḢLEG corresponded to 240% of the resting heat production. HLEG was increased by higher wind speed and lower air temperature, but it became essentially independent of wind speed above 37·5 km h−1. The maximum values of ḢLEG were 4–6 times as large as the resting heat production and could account for 50–65 % of the total heat produced during flight. It is concluded that in a non-aquatic bird the legs and feet can play a major role in whole-body thermoregulation, both at rest and during flight.