The Cooling Power of Pigeon Legs

The rate of heat loss from legs and feet (HLEG) w a s studied in resting pigeons preheated to a body temperature (43-l°C) close to those recorded during flight. The experimental system was designed to allow the calculation of HLEG from whole-body cooling rates following exposure of the legs and feet to various combinations of wind speed (0-75 km h") 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~ wind at 25°C, HLE G corresponded to 240% of the resting heat production. HLEG w a s increased by higher wind speed and lower air temperature, but it became essentially independent of wind speed above 37-5 km h~'. The maximum values of HL E G 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.