The toucan uses its enormous bill as a heat-exchange surface to help regulate body temperature.
Toucans are tropical American birds in the family Ramphastidae. Their bills look heavy, but they are built from a lightweight honeycomb structure covered in keratin. This design allows the bird to carry a large bill without the mass suggested by its size.
Blood vessels in the bill can move warm blood toward the surface, where heat is released to the surrounding air. By adjusting blood flow, a toucan can use the bill as a radiator. This function supplements, rather than replaces, normal cooling behaviours such as panting.
The bill also helps with feeding, fruit handling, display, and defense. Toucans are not the only birds with large bills; hornbills and shoebills are separate groups with different anatomy and geographic ranges.