The toucans of the Amazon rainforest and the hornbills of Asian and African rainforests appear to be very similar but are not closely related - an example of convergent evolution.

Convergent evolution occurs when animals that are unrelated, yet occupy similar ecological niches, evolve similar characteristics in order to thrive in those niches.

Both toucans and hornbills live in the emergent trees of the rainforest.

The large bills of toucans and hornbills make them easy to identify. The birds use these bills to feed on fruits and berries.

It is hard to say why these beaks - which appear to make feeding awkward - evolved.

While they are useful for reaching berries on thin, weak twigs, which would not support the bird's weight, a long, slender beak would serve the same purpose.

While the beaks may look formidable-in some toucans the beak is longer than the bird's body-they do not deter a determined predator.

It is possible that these bills serve as a flag to aid in species and mate recognition.

They may also be used for heat regulation.


Toucans are 12 to 24 inches (30 to 60cm) long and make their nests in high natural tree holes, which they enlarge by removing rotten wood.

Gregarious birds, toucans move about in groups of a dozen or so.

They are weak fliers and merely glide short distances between trees. The tail, unlike that of most birds, moves up and down during flight.

When sleeping, the toucan lays its huge bill along its back, covering it with its tail.


Hornbills are larger-about 2 to 5 feet (60cm to 1.5m) long. The beak is similar to the toucan's, but bears a casque - a horny outgrowth along the top.

The hornbill's casque is usually a light, honeycomb structure with plenty of air spaces. It probably acts as a resonating chamber to amplify the bird's calls.

The Asian helmeted hornbill is an exception. It has a solid casque of ivory - red on the outside, yellow on the inside.

Hornbills have well-developed eyelashes - an unusual feature among birds.

They supplement their fruit and berry diet with insects, tree frogs, eggs and the nestlings of other birds.

Hornbills  move about in small groups.

They  fly well but noisily because of the air which rushes through the gaps in their wings between the primary feather quills. Other feathers, known as coverts, usually cover these gaps. In hornbills, these small feathers are greatly reduced.

The voices of hornbills are loud but unmelodious. The casqued hornbill of Africa sounds like a braying donkey.

Many hornbill species have long tail feathers. Young hornbills nesting in tree holes hold their tail feathers upright so they can fit in their nests.