from: Cosmos Magazine
SYDNEY: The toucan's brightly coloured bill isn't all for show, says a new study, which suggests the curious feature may function as an efficient way for the bird to stay cool in the steamy Amazon Rainforest.
The research, detailed today in the U.S. journal Science proposes that - much like elephants' ears - the toucan's beak may operate as a thermal radiator, releasing body heat when the bird needs to cool down
"By altering blood flow to the bill's surface, toucans can conserve body heat when it is cold, or cope with heat stress by increasing blood flow," said study lead author Glenn Tattersall of Brock University in Ontario, Canada.
Bills, bills, bills
These highly social residents of the Amazon rainforest (Ramphastos toco) have bills that make up approximately one-third of their total body length so researchers wondered if they had a hidden purpose.
"Birds do not sweat, so must cope with other mechanisms to deal with elevated temperatures," said Tattersall.
The researchers monitored captive toucans with infrared thermal imaging cameras (much like the ones currently being used in airports to scan travellers for swine flu), while the birds were exposed to a range of air temperatures from 10 to 35°C. They observed that the bill's surface temperature changed quickly as its environment warmed or cooled.
"The difference between bill temperature and air temperature was an indication of heat loss. A large difference indicated high heat loss, a small difference meant there was little blood flow, and therefore little heat loss," he said.
Critical temperature
According to Winston Lancaster, a functional morphologist at California State University in Sacramento, U.S., regulation of body heat is critical for warm-blooded animals like birds and mammals.
Although they have a range of body temperatures over which they can function, the normal resting temperature is near the upper limit of this range, meaning that physical activity can lead to rapid overheating.
"This is particularly critical for birds as flight is such an energetically demanding activity… Of course, it can be especially critical for tropical birds," said Lancaster. "This study will likely inspire someone to examine the beaks of other tropical birds for this function, such as storks, hornbills, spoonbills and flamingos."
Ty Hoffman, an expert on thermoregulation at Phoenix College, in Arizona, commented that the significance of the study lies in the amount of heat the toucan's bill is able to release. The study reported adult toucans could release up to four times the amount of heat their bodies produce when they are at rest.
"These results not only help us to better understand what has been a bit of a puzzle - why toucans would have such enormous bills - but they suggest that there might be a thermoregulatory function for similarly odd structures found in other animals," said Hoffmann.
Tattersall said that the results might overturn the idea that the size and shape of bird bills are primarily driven by diet.
He added the findings might also be extrapolated to certain species of dinosaur, which have bony plates thought to be thermal radiators for heat exchange.