On our Central America cruise one of the bird species most sought-after are members of the family Ramphastidae: the toucans, toucanets, and araçaris. They are brightly marked and are renowned for thier large, colorful bills. The family includes five genera and about forty different species. The name of this bird group is derived from the Tupi language of South America.
Both the largest and smallest of the toucans are found in South America, and 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). Some of the species we see regularly on our Panama and Costa Rica cruise are the small emerald toucanet and yellow-eared toucanet, fiery-billed araçari, collared araçari, and among the largest, the keeled-bill toucan and the chestnut-mandibled toucan.
In all toucans their bodies are short (about the size of a crow) and compact, the tail rounded and varies in length, from half the length to the whole length of the body. A structural complex probably unique to toucans involves the modification of several tail vertebrae. The rear three vertebrae are fused and attached to the spine by a ball and socket joint. Because of this, toucans may bring their tail forwards until it touches the head. This is the posture in which they sleep, often appearing simply as a ball of feathers, with the tip of the tail sticking out over the head. The legs of a toucan are strong and relatively short with their toes arranged in a zygodactyl pattern (same as woodpeckers, in pairs with the first and fourth toes turned backwards).
There is no discerable sexual dimorphism in toucans, however, the bills of female toucans are usually shorter, deeper and sometimes straighter. The feathers in the genus Ramphastos containing the largest toucans such as the chestnut-mandibled toucan and keel-billed toucan that we see on our Costa Rica and Panama cruise, are generally black, with touches of white, yellow, and scarlet. The underparts of the araçaris (small toucans) are yellow, crossed by one or more black or red bands. The toucanets have mostly green plumage with blue markings.
The colorful, giant bill, which in some large species measure more than half the length of the body, is the hallmark of toucans. Despite its size it is very light, being composed of bone struts filled with spongy tissue of keratin between them. The beaks of toucans have always been of interest because of their extraordinary shape, color and size, once being called “grossly monstrous” by Buffon in the 18th century. The beaks definitely aid in their feeding behavior as it allows an individual to perch in one spot and reach for all fruit in range, thereby reducing energy expenditure. Another theory mentions that the bill may be for intimidation of smaller birds so that the toucan may plunder nests undisturbed. However, the latest research has discovered that the large bill of the toucan is a also a highly efficient thermoregulation system. It appears toucans can regulate heat distribution by modifying blood flow. Apparently, the toucan's bill is, relative to its size, one of the largest thermal windows in the animal kingdom, out-doing elephants’ ears in its ability to radiate body heat.
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 toucans are primarily frugivorous (fruit eating), but are opportunistically omnivorous and will take prey such as insects, small lizards as well as smaller birds, taking as well eggs and nestlings. This probably provides a crucial addition of protein to their diet. However, in their range, toucans are the dominant frugivores, and as such play an extremely important ecological role as vectors for seed dispersal of fruiting trees.
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