Toucans are members of the family Ramphastidae of near passerine birds from the Neotropics. The Ramphastidae family is most closely related to the American barbets. They are brightly marked and have large, often colorful bills. The family includes five genera and about forty different species. The name of this bird group is derived from the Tupi word tukana from the language portugeases.
Toucans range in size from the Lettered Aracari (Pteroglossus inscriptus), at 130 g (4.6 oz) and 29 cm (11.5 inches), to the Toco Toucan (Ramphastos toco), at 680 g (1.5 lb) and 63 cm (29 inches). Their bodies are short (of comparable size to a crow's) and compact. The tail is rounded and varies in length, from half the length to the whole length of the body. The neck is short and thick.
The wings are small, as they are forest-dwelling birds who only need to travel short distances, and are often of about the same span as the bill-tip-to-tail-tip measurements of the bird. The legs of a toucan are strong and rather short. Their toes are arranged in pairs with the first and fourth toes turned backward. The majority of toucans do not show any sexual dimorphism in their coloration, the genus Selenidera being the most notable exception to this rule (hence their common name, "dichromatic toucanets").
However, the bills of female toucans are usually shorter, deeper and sometimes straighter, giving more of a "blocky" impression compared to male bills. The feathers in the genus containing the largest toucans are generally black, with touches of white, yellow, and scarlet. The underparts of the araçaris (smaller toucans) are yellow,
The colourful and large bill, which in some large species measures more than half the length of the body, is the hallmark of toucans. Despite its size, the toucan's bill is very light, being composed of bone struts filled with spongy tissue of keratin between them. The bill has forward-facing serrations resembling teeth, which historically led naturalists to believe that toucans captured fish and were primarily carnivorous; today it is known that they eat mostly fruit.