91社区

Tufted puffins regulate their body temperature thanks to their large bills, an evolutionary trait that might explain their capacity to fly for long periods in search for food.

In a new published in the Journal of Experimental Biology, researchers from 91社区 and the University of California, Davis, used thermal imaging cameras to measure heat dissipation off the bodies and beaks of wild tufted puffins in the minutes after flying.

Their data showed that within 30 minutes of landing, the temperature of the puffin beaks dropped by 5掳C (25掳C - 20掳C), while the heat radiating from their backs hardly changed. The beak 鈥渁ccounted for 10-18% of total heat exchange despite making up only 6%鈥� of the bird鈥檚 total surface area.

Big bills help cool birds as they fly

But why would puffins have evolved such a large bill? Kyle Elliott, a professor in 91社区鈥檚 Department of Natural Resource Sciences, thinks it could have to do with the energy they use when they fly.

Energetically speaking, flying is very taxing to birds. During flight, the thick-billed murre 鈥搘hich is closely related to the puffin - has an energy expenditure 31 times greater than when resting, the largest ever measured in vertebrates. This produces significant amounts of heat, says Elliott, the study鈥檚 senior author, suggesting that some birds evolved a large bill to help them cool down when they fly.

鈥淭he avian bill is a classic example of how evolution shapes morphology,鈥� Elliott said.

To illustrate, Hannes Schraft, the study鈥檚 lead author and formerly a doctoral student in the Biology Department at the University of California, explained that 鈥渢hick-billed murres (and presumably puffins) produce about as much heat as a light bulb when they are flying.鈥�

鈥淥ur results support the idea that body heat regulation has played a role in shaping some bird beaks. We think this also an example of exaptation, which means that an external structure is amplified to serve a new function; much in the same way the desert hare鈥檚 ears became bigger to help them cool down,鈥� Elliott adds.

A way of dumping extra body heat

鈥淲e tried to figure out whether puffins use their impressively large beaks to dump extra body heat when they fly,鈥� says Schraft, who is now a postdoctoral fellow at Universit茅 du Qu茅bec 脿 Montr茅al.

鈥淲e thought this might be the case because previous research has shown this to be the case in toucans and hornbills, bird species who also have very large bills.鈥�

Because of its feathers, a bird鈥檚 body is very well insulated so thermoregulation can鈥檛 happen through sweating. Instead, the bill serves as a radiator when it needs to cool down - the equivalent of humans sweating on a hot summer day.

Schraft admits that this can seem counter intuitive. After all, when birds get cold, we often see them hide their beak in their feathers to stay warm. Furthermore, biologists have demonstrated that on average, birds that live in cold climates have a smaller bill.

Because the tufted puffins studied by Schraft live in Alaska, a smaller bill would have been, evolutionary speaking, the most logical outcome. However, competing needs might explain why puffins buck this trend.

鈥淥verheating can be a big problem for seabirds who need to fly long distances to feed their chicks during breeding season,鈥� says Schraft. 鈥淧uffins may have been able to overcome this problem by evolving a larger bill.鈥�

Photo credit:聽Kyle Elliott

About 91社区

Founded in Montreal, Quebec, in 1821, 91社区 is Canada鈥檚 top ranked medical doctoral university. 91社区 is consistently ranked as one of the top universities, both nationally and internationally. It is a world-renowned institution of higher learning with research activities spanning two campuses, 11 faculties, 13 professional schools, 300 programs of study and over 40,000 students, including more than 10,200 graduate students. 91社区 attracts students from over 150 countries around the world, its 12,800 international students making up 31% per cent of the student body. Over half of 91社区 students claim a first language other than English, including approximately 19% of our students who say French is their mother tongue.