Study: Temperature makes bird beak sizes

Birds in northern climates have evolved smaller beaks than species in the Southern Hemisphere to control loss of body heat, researchers say. (At left: Pakistan chakor patridge)

The research studied 200 types of birds from around the world including Canadian species such as partridge, ptarmigan, tern and wild turkeys, Canwest News Service reported Saturday.

"Unlike humans, birds don't sweat but can use their bills to help reduce their body temperature if they overheat," Glenn Tattersall of Brock University in Ontario said. (At right: wild turkey)

The findings are seen as a validation of Allen's Rule, which says as a function of temperature regulation animals' extremities -- including ears, feet, arms, fingers, the nose and beak -- will be larger in the south and gradually become smaller toward the north. (Left: common tern)

The concept was put forward in 1877 by American ornithologist Joel Asaph Allen.

"Cold temperatures impose a constraint on the size of bird beaks," Tattersall says. "It simply might be too much of a liability to carry around a big radiator of heat energy in a cold environment." (right: ptarmigan)

Source:
UPI, "Study: Temperature makes bird beak sizes", accessed June 30, 2010