Oversized Beak Keeps Toucan Cool

It turns out there’s more to a toucan’s bill than pretty colors and a penchant for Fruit Loops.

Originally described as “grossly monstrous” by the Comte de Buffon, the toucan's beak was theorized by Charles Darwin to be related to sexual selection. The toucans with the biggest bills were thought to have the most success attracting a mate and reproducing, the same explanation used for the extravagant plumes on peacocks.

​However, scientists now have evidence that the long beak of a toucan regulates heat distribution, acting as a thermal radiator of sorts. Glenn J. Tattersall of Brock University and Denis V. Andrade and Augusto S. Abe of Sao Paulo State University studied the toco toucan (Ramphastos toco), the largest member of the toucan family that also has the largest bill relative to body size of any bird.

Using infrared thermography and thermal imaging cameras, the team monitored the toucans’ response in a temperature-controlled chamber. Below a temperature of about 60 degrees Fahrenheit, the beak was somewhat colder than ambient temperature, meaning that the blood vessels between the bony core of the bill and its hornlike covering were constricted.

Conversely, as temperatures increased above 70 degrees, blood flow increased, making the bill warmer and helping the bird cope with the extra heat load.

In a recent paper published in Science researchers note:

Our results indicate that the toucan’s bills 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 ... Given the rapid radiation of bill structures and diversity of beak morphologies of birds, thermal constraints from bill heat loss may prove to be a common feature among many avian fauna.