Why Do Toucans Have Big Beaks? Light, Hollow and Cool

Reaching fruit: the classic explanation

Toucans eat mostly fruit, and many of the best fruits grow at the tips of branches. A toucan is a fairly heavy bird, so it cannot perch on the thinnest twigs. With a long bill, it can sit on a sturdy branch and reach out to pick fruit that smaller-billed birds of the same size could not get.

The bill also works like a pair of tongs. A toucan grasps a fruit at the tip, then tosses its head back to throw the food into its throat. The cutting edges of the bill are finely serrated, which helps it grip slippery fruit and tear off pieces of larger fruits. Read more about the diet in what do toucans eat?.

A long bill is also useful for reaching into tree holes and the hanging nests of other birds, where toucans take eggs and chicks. This may help explain why some small birds react to toucans as if they were predators.

A built-in radiator

For a long time the size of the toucan bill seemed out of proportion to its food. In 2009, a team led by Glenn Tattersall of Brock University in Canada, working with Brazilian biologists Denis Andrade and Augusto Abe, published a study in the journal Science on the toco toucan, the largest toucan.

Using infrared cameras, they showed that the bill acts as a controllable radiator. The bill has a dense network of blood vessels just beneath its surface. When the bird is warm, it widens these vessels, the bill heats up and body heat flows out into the air. When the bird is cool, the vessels narrow and the bill stays cool, saving heat.

The researchers found that the bill, which makes up about 30–50% of the bird’s total surface area, could release anywhere from a small share to a large majority of the toucan’s resting heat production, depending on temperature and air flow. Relative to body size, it is one of the largest heat-exchange organs known in any animal, compared by the authors to the ears of an elephant.

This also helps explain a familiar sleeping posture. A resting toucan turns its head and tucks its bill under its wing or along its back, which may help reduce heat loss through the bill on cool nights.

Why the beak is so light

A bill that large would be a burden if it were solid. Instead, the toucan bill is a lightweight structure that materials scientists have studied in detail. A 2005 study by Yasuaki Seki, Matthew Schneider and Marc Meyers at the University of California, San Diego, described it as a sandwich design.

The outside is a thin shell of keratin, the protein that also makes up hair, nails and feathers, arranged in overlapping layers like tiny tiles. Inside is a light, foam-like core of thin bony struts surrounding air spaces. Together they make a bill that is stiff and strong but has a very low weight for its size, much like a modern lightweight panel used in engineering.

This is why toucans can fly and balance easily despite the size of their bills, as explained in can toucans fly?.

Display, courtship and recognition

The bright colors of toucan bills are no accident. Each species has its own pattern of colors and markings, from the orange bill with a black tip of the toco toucan to the rainbow bill of the keel-billed toucan of Central America. These patterns probably help toucans recognize their own species.

Bills also seem to play a role in social life. Toucans in pairs and groups touch, tap and gently “fence” with their bills, and pairs often preen each other. Males of some species may use their bills in courtship displays, and the bill may help signal status to rivals at fruiting trees.

Do toucans have teeth?

The jagged edges of a toucan bill look a little like teeth, but they are not. Like all living birds, toucans have no true teeth. The serrations are part of the keratin covering and simply help the bird grip food. Other birds have similar tooth-like edges, as explained in do birds have teeth?.

Myths about toucan beaks

Myth: a toucan’s beak is heavy. It is the opposite. The bill is built of a thin keratin shell over a foam-like bony core and is very light for its size.

Myth: toucans use their beaks to crack nuts like parrots. Toucans have relatively weak bites compared with parrots and mostly eat soft fruit. Their bill is a reaching and grasping tool, not a nutcracker.

Fact: there is probably no single reason for the big beak. Most biologists think several advantages, including feeding, heat control and display, together explain why toucans evolved such remarkable bills.