Birds reduce their heating bills in cold climates

June 23, 2010
This is a toco toucan, Ramphastos toco. Credit: Glenn Tattersall

The evolution of bird bills is related to climate according to latest research by the University of Melbourne, Australia and Brock University, Canada.

By examining bill sizes of a diverse range of bird species around the world, researchers have found that birds with larger bills tend to be found in hot environments, whilst birds in colder environments have evolved smaller bills.

The study led by Dr Matt Symonds of the Department of Zoology at the University of Melbourne and Dr Glenn Tattersall of the Department of Biological Sciences at Brock University provides evidence that maintaining body temperature in a bird's natural environment may have shaped the evolution of bird bills.

The size and shape of these distinctive structures are usually explained by their role in feeding and mate attraction. However, previous research shows bird bills have a third, less appreciated function, as organs of heat exchange.

Dr Glenn Tattersall says we know, from our studies that birds like toucans and geese can lose a large amount of their through their bills.

"Unlike humans they don't sweat but can use their bills to help reduce their body temperature if they overheat."

"We then wondered whether this function had evolutionary consequences, and sought to compare bill sizes across a whole range of species," says Dr Tattersall.

The 214 species examined comprised diverse groups including toucans, African barbets and tinkerbirds, Australian parrots, grass , Canadian gamebirds, penguins, gulls and terns.

"Across all species, there were strong links between bill length and both latitude, altitude and environmental temperature," Dr Matt Symonds says. "Species that have to deal with colder temperatures have smaller bills."

"This suggests that there is an evolutionary connection between the size of the birds' bills and their role in heat management," he says.

Although it's possible that large bills have evolved to help shed heat loads and prevent overheating in hot climates, we think it's more likely that cold temperatures impose a constraint on the size of bird beaks," Dr Tattersall says.

"It simply might be too much of a liability to carry around a big radiator of heat energy in a cold environment."

The research validates a 133-year-old ecological theory called Allen's rule, which predicts that animal appendages like limbs, ears, and tails are smaller in cold climates in order to minimize heat loss.

Dr Symonds says Allen's rule has never been tested with this large a group of animals and was more anecdotal.

"This is the first rigorous study of its kind to test this theory and to show that bird bills have evolved in this manner."

Explore further: Australian expert rejects bird flu fears

More information: The paper is published online this week in the journal American Naturalist and will be in the journal's August 2010 edition.

Related Stories

Australian expert rejects bird flu fears

November 3, 2005

A bird medicine specialist says the risk of human bird flu infection is small in Australia and people may still safely eat chicken and keep pet birds.

Study: We really do like larger bills

January 31, 2006

A University of Iowa money study explores our preference for big bills over small ones -- and explains our marked reluctance to part with a larger bill.

Big-brained birds survive better in nature

January 10, 2007

Birds with brains that are large in relation to their body size have a lower mortality rate than those with smaller brains, according to new research published in the journal Proceedings of the Royal Society B: Biological ...

Who can cool his body fast? Toucan

July 23, 2009

(AP) -- The toucan's colorful bill gives new meaning to the phrase cool dude. Indeed, that gigantic schnoz turns out to be a radiator the rain forest dweller uses to lose body heat. The bill of the Toco Toucan makes up about ...

Recommended for you

Scientists debate boundaries, ethics of human gene editing

December 1, 2015

Rewriting your DNA is getting closer to reality: A revolutionary technology is opening new frontiers for genetic engineering—a promise of cures for intractable diseases along with anxiety about designer babies.

Which came first—the sponge or the comb jelly?

December 1, 2015

Bristol study reaffirms classical view of early animal evolution. Whether sponges or comb jellies (also known as sea gooseberries) represent the oldest extant animal phylum is of crucial importance to our understanding of ...

Trap-jaw ants exhibit previously unseen jumping behavior

December 1, 2015

A species of trap-jaw ant has been found to exhibit a previously unseen jumping behavior, using its legs rather than its powerful jaws. The discovery makes this species, Odontomachus rixosus, the only species of ant that ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.