Why Toucans have such large beaks
A team of scientists appears to have discovered why the toucan (Thiago Filadelpho) has such a large beak. It has the largest bill of any bird relative to the size of its body - making up about one-third of its total body length. This has puzzled scientists for centuries, and various concepts have been forthcoming about the reason. Charles Darwin thought it might be to attract mates. Others thought it might have something to do with peeling fruit, nest predation or visual warnings.
According to a report from the BBC, however, one team might of scientists might just have the answer. Writing in the journal, Science, the researchers say that the toucan uses its enormous beak to stay cool.
Infrared cameras were used to show how this remarkable bird manages to transfer heat from its body into its bill, thus helping to regulate its body temperature.
The researchers - from Brock University, Canada, and Universidade Estadual Paulista, Brazil, looked at the toco toucan (Ramphastos toco), which has the biggest bill of all. Dr Glenn Tattersall of Brock University, the lead author of the paper, said: “We used infrared thermal imaging technology to assess the surface temperature of the bill of toucans while they were encountering a range of air temperatures from 10C to 35C. This allowed us to measure the exact temperature of the bill.”
The scientists found that as the surroundings got warmer, the toucan’s bill would rapidly heat up, effectively acting as a radiator to draw heat away from the bird’s body, and - in cooler temperatures - little heat would radiate from the bill, allowing the the bird to conserve its warmth. This was particularly noticeable at night, apparently. At sunset, birds would pump out heat from their beaks within minutes, lowering their body temperature as they slept.
The toucan’s bill has a network of blood vessels that can increase or restrict the flow of blood. “By altering blood flow to the bill’s surface,” said Dr Tattersall, “toucans can conserve body heat when it is cold or cope with heat stress by increasing blood flow. Essentially, the large surface area of the bill, and the fact it is not insulated, means that the blood flowing through is able to release heat into the bill, thus cooling the bird. This blood-derived heat in the bill is then dissipated into the air.”
It’s known that other animals also use parts of their bodies to regulate their body temperature. Elephants and rabbits, for example, radiate heat from their ears to cool down, but the size of the toucan’s bill means that, relatively, it has one of the largest of what’s described as a “thermal window” amongst animals.
“Bird bills are not ‘dead tissues’, incapable of playing a role in heat balance,” explained Dr Tattersall, “but are active contributors to thermoregulation. Birds do not sweat, so must cope with other mechanisms to deal with elevated temperatures.”
This doesn’t necessarily mean that there aren’t other functions for the toucan’s beak, say the researchers, who now plan to look at other birds to see whether their bills too are involved with temperature regulation.
