In its capacity to remove body heat the bill is comparable to that of elephant ears. The ability to radiate heat depends upon air speed: if this is low only 25% of the adult bird's resting heat production to as much as four times this heat production. In comparison, the bill of a duck and the ears of elephant can shed only about 9% of resting heat production. The bill normally is responsible for 30 to 60% of heat loss. The practice of toco toucans of placing their bills under their wings may serve to insulate the bill and reduce heat loss during sleep. It has been observed that "complexities of the vasculature and controlling mechanisms needed to adjust the blood flow to the bill may not be completely developed until