COLUMBUS , Ohio In the steamy tropics, even the birds find the pace of life a bit more relaxed, research shows.

Tropical birds expend less energy at rest than do birds living in more northern climates, according to a study published online this week in the Proceedings of the National Academy of Sciences.

"We found that tropical birds have a slow pace of life which is reflected in how much energy they spend to stay alive," said Joseph Williams, co-author of the study and associate professor of evolution, ecology and organismal biology at Ohio State University.

"This is the first time this has been confirmed in birds."

The findings of a slower pace of life in tropical birds correspond to other aspects of the lives of tropical birds, such as their longer life and slower growth.

"Lower energy use fits with the life history of these tropical birds, which is different than those living in temperate climates," said co-author Popko Wiersma, a postdoctoral researcher at Ohio State . Tropical birds live longer, lay fewer eggs and their chicks grow slower than those of temperate birds.

The researchers traveled to Panama where they captured 69 species of tropical birds and measured their basal metabolic rate (BMR) the minimum amount of energy they expend at rest, solely to maintain their vital bodily functions. This was the largest data set ever collected of metabolic rates of tropical birds.

They compared these measurements with the BMRs of 59 species of temperate birds.

They found that tropical birds used about 18 percent less energy, as measured by BMR, when compared with temperate birds.

To further test this association, the researchers also compared BMRs in related species pairs. These were birds from the same genus or family, such as flycatchers or swallows, in which one of the pair lived its life in the tropics and one lived in temperate zones.

Even here, the tropical
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Contact: Popko Wiersma
Wiersma.6@osu.edu
614-292-3393
Ohio State University
22-May-2007