Still frames from one of the study videos showing heat being radiated from the bill of a toucan.
Credit: Glenn Tattersall
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."
