A new study offers some clues about how small aquatic birds survive in extremely cold climates.
Staying warm is hard work for aquatic birds. Heat loss is around twenty times greater in water than in air, so aquatic birds have to increase their resting metabolism to generate heat on the water. Heat loss is an even greater issue for small birds, so it was assumed that small birds would have to increase their metabolism in water even more than large birds do.
But according to a study by researchers at the University of Wyoming, that's not always the case. The researchers studied the metabolism of Cassin's auklets, a small sea bird found throughout the Northern Pacific Ocean. They found that auklets do increase their metabolism on the water, but not as much proportionately as some larger birds do.
In fact, ducks, auks, cormorants, and small penguins responded quite differently to air and water temperatures, perhaps reflecting very different demands during evolutionary history.
The research is published in the May/June 2011 issue of the journal Physiological and Biochemical Zoology.
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