The Cooling Power of Pigeon Wings

The rate of heat loss through the stretched wings (Ḣwings) was studied in resting pigeons preheated to a body temperature (43.7°C) within the range of those recorded during flight. The experimental system was designed to allow the calculation of Ḣwings from the increase in whole-body cooling rates resulting from exposure of the wings to various wind speeds (0–50 km h−1) at 23°C. The maximum value of Ḣwings was 3.8 W, less than twice the heat production of a resting pigeon. This indicates that the contribution of the wings to heat dissipation during flight may not be nearly as important as has been supposed. At low windspeeds (0–12.5 km h−1), Ḣwings corresponded to about 40% of the resting rate of heat production, and this value is discussed in connection with the various wing postures observed in hyperthermic birds.