Glenn Tattersall

A Brock researcher has co-authored a study showing that the evolution of bird bills is related to the climate in which they live.

Glenn Tattersall, a professor of Biological Sciences, studied the issue with Matt Symonds in the Department of Zoology at the University of Melbourne in Australia. They found that birds with larger bills tend to be found in hot environments, while birds with smaller bills live in cooler climates.

“A lot of questions have been based on the notion that bill size is strictly determined by food type or body size,” Tattersall said. “This is interjecting another idea: that the environment itself plays a role in the bill size of these birds.”

The study validates an ecological theory called Allen’s rule, which predicts that animal appendages like limbs, ears and tails are smaller in colder climates to minimize heat loss. Prior to this study, however, little emphasis has been placed on the possibility that bills would be subject to similar constraints.

To reach the conclusion, Tattersall and Symonds used existing data to study 214 species of birds, including penguins, toucans, gulls and terns. They chose mainly non-migratory birds, or birds with reasonably defined geographic ranges, Tattersall said.

The paper was published online this week in the journal American Naturalist and will be in the journal’s August 2010 edition. It is located at journals.uchicago.edu/action/showForthcomingToc?journalCode=an&