Toucan

Toucans (/ˈtuːkæn/, UK: /-kən/) are members of the Neotropical near passerine bird family Ramphastidae. The Ramphastidae are most closely related to the American barbets. They are brightly marked and have large, often-colorful bills. The family includes five genera and over forty different species. Toucans are arboreal and typically lay 2–21 white eggs in their nests. They make their nests in tree hollows and holes excavated by other animals such as woodpeckers—the toucan bill has very limited use as an excavation tool. When the eggs hatch, the young emerge completely naked, without any down. Toucans are resident breeders and do not migrate. Toucans are usually found in pairs or small flocks. They sometimes fence with their bills and wrestle, which scientists hypothesize they do to establish dominance hierarchies. The name of this bird group is derived from the Tupi word tukana, via Portuguese. The family includes toucans, aracaris and toucanets; more distant relatives include various families of barbets and woodpeckers in the suborder Pici. The toucan family has five extant genera as follows: 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 the 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 purple, with touches of white, yellow, and scarlet, and black. The underparts of the araçaris (smaller toucans) are yellow, crossed by one or more black or red bands. The toucanets, have mostly green plumage with blue markings. The colorful 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. This deep light-weight construction is the most efficient in terms of strength/weight ratio - like a bridge truss as compared to a beam - so would explain the depth of the bill in the absence of any adaptive penalties associated with a deeper bill as compared with a more compact bill of equal length, which would have to be heavier. 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. Researchers have discovered that the large bill of the toucan is a highly efficient thermoregulation system, though its size may still be advantageous in other ways. It does aid in their feeding behavior (as they sit in one spot and reach for all fruit in range, thereby reducing energy expenditure), and it has also been theorized that the bill may intimidate smaller birds, so that the toucan may plunder nests undisturbed (see Diet below). The beak allows the bird to reach deep into tree-holes to access food unavailable to other birds, and also to ransack suspended nests built by smaller birds.