Bird age: 12 months
Bid Weight: 1 146 lbs
The toco toucan has conspicuously contrasting plumage with a mainly black body, a white throat, chest and uppertail-coverts, and red undertail-coverts. What appears to be a blue iris is actually thin blue skin around the eye. This blue skin is surrounded by another ring of bare, orange skin. The most noticeable feature, however, is its huge bill, which measures from 15.8 to 23 cm (6+1⁄4 to 9 in) in length, which is yellow-orange, tending to deeper reddish-orange on its lower sections and culmen, and with a black base and large spot on the tip. It looks heavy, but as in other toucans it is relatively light because the inside largely is hollow. The tongue is nearly as long as the bill and very flat. This species is the largest toucan and the largest representative of the order Piciformes. The total length of the species is 55–65 cm (21+1⁄2–25+1⁄2 in). Body weight in these birds can vary from 500 to 876 g (1 lb 1+5⁄8 oz to 1 lb 14+7⁄8 oz), with males averaging 723 g (1 lb 9+1⁄2 oz) against the smaller female, which averages 576 g (1 lb 4+3⁄8 oz). Among standard measurements, the wing chord is 22 to 26 cm (8+1⁄2 to 10 in), the tail is 14.1 to 17.9 cm (5+9⁄16 to 7+1⁄16 in) and the tarsus is 4.8 to 6.5 cm (1+7⁄8 to 2+9⁄16 in). Other than the size difference, there are no external differences between the sexes. Juveniles are duller and shorter-billed than adults. Its voice consists of a deep, coarse croaking, often repeated every few seconds. It also has a rattling call and will bill-clack.
The bill is the largest relative to body size of all birds providing 30 to 50% of its body surface area, although another Neotropical species, the sword-billed hummingbird, has a longer bill relative to its body length. It was called by Buffon a “grossly monstrous” appendage.
Diverse functions have been suggested. Charles Darwin suggested it was a sexual ornament: “toucans may owe the enormous size of their beaks to sexual selection, for the sake of displaying the diversified and vivid stripes of colour with which these organs are ornamented”. Further suggestions have included aid in peeling fruit, intimidating other birds when robbing their nests, social selection related to defense of territory, and as a visual warning.
Research has shown that one function is as a surface area for heat exchange. The bill has the ability to modify blood flow and so regulate heat distribution in the body, allowing it to use its bill as a thermal radiator. In terms of surface area used for this function, the bill relative to the bird’s size is amongst the largest of any animal and has a network of superficial blood vessels supporting the thin horny sheath on the bill made of keratin called the rhamphotheca.
In its capacity to remove body heat the bill is comparable to that of elephant ears. The ability to radiate heat depends upon air speed: if this is low only 25% of the adult bird’s resting heat production to as much as four times this heat production. In comparison, the bill of a duck and the ears of elephant can shed only about 9% of resting heat production. The bill normally is responsible for 30 to 60% of heat loss. The practice of toco toucans of placing their bills under their wings may serve to insulate the bill and reduce heat loss during sleep. It has been observed that “complexities of the vasculature and controlling mechanisms needed to adjust the blood flow to the bill may not be completely developed until adulthood.