The Toco Toucan, the largest member of the toucan family, possesses the largest beak relative to body size of all birds. Its bill has a network of superficial blood vessels supporting the horny ramphoteca at the tip of the upper bill, providing a significant surface area for heat exchange. The capacity of the toco toucan to regulate heat distribution by modifying blood flow was shown using infrared measurements on different regions of the bird's body. It appears that toucan's bill is, relative to its size, one of the largest thermal windows in the animal kingdom, rivaling elephants’ ears in its ability to radiate body heat.

http://en.wikipedia.org/wiki/Toucan