Tuesday, July 27, 2010

Big Beaks are Cool

Bird beaks can tell us a lot about the eating strategies of a bird.  Beaks have evolved to accommodate the foods of preference as seen at Wikipedia.  The beak is technically the keratinized tissue on the outer part of the mouth (think hard lips), while the whole mouth structure is referred to as the bill.  A good discussion of bill development is at birdchannel.com.
It turns out that beaks may also play a role in controlling some bird's temperature.  Toucans, the Jimmy Durante* of the bird world, were shown in a 2009 study to use their huge beaks for temperature regulation.  The scientists used infrared thermal imaging to measure the surface temperature of the bill of toucans which were in a wide range of ambient temperatures.
“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.  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,” the scientist adds.  Previous studies have determined that the beak is laced with an intricate network of blood vessels that have the ability to control the amount of blood reaching it.

“Bird bills are not 'dead tissues,' incapable of playing a role in heat balance, but are active contributors to thermoregulation.  Birds do not sweat, so must cope with other mechanisms to deal with elevated temperatures.
Now new studies by the same scientists suggest that bird beak size has evolved to adapt to the temperature of their habitat.  According to Science Daily, Dr Glenn Tattersall and associates examined 214 species across a broad range of beak types and climates.
"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.
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."
Arctic Tern- Wikipedia
One theory is that larger bills evolve for shedding more heat in warm latitudes.  These investigators feel it is more likely that big heat shedding beaks are a liability in cold climes.  In other words, you are not likely to find hot "lips" in the arctic. 

* Too young for Jimmy Durante? click here to see him.


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