Birds of paradise.

• Author: Hardman, Chris
• Position: Tropical bird's energy use and metabolism

PEOPLE ARE ATTRACTED to the tropical regions of the Americas for the beautiful weather and relaxed lifestyle. High humidity and blazing sun encourages us all to take it slow. In a recent study, scientists have found that the birds in the tropics have a slower pace of life as well. By comparing tropical and temperate birds' basal metabolic rate (BMR)--the amount of energy spent to breathe and live while at rest--scientists discovered that the tropical birds use less energy to maintain normal bodily functions than their temperate cousins.

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"We found that tropical birds have a slow pace of life which is reflected in how much energy they spend to stay alive," says professor Joseph Williams of Ohio State University. "This is the first time this has been confirmed in birds." Williams is co-author, with fellow Ohio State researcher Popko Wiersma, of a study published online in the journal Proceedings of the National Academy of Sciences.

In a unique experiment, researchers mist-netted 69 species of birds in the tropical lowland forests of Gamboa, Panama, and measured their basal metabolic rate when the birds were resting. For the temperate species, the team tracked the BMR of thirteen species of birds living near Columbus, Ohio. The data showed that the tropical species used about eighteen percent less energy to maintain normal bodily functions than the temperate species.

"Lower energy use fits with the life history of these tropical birds, which is different than those living in temperate climates," says Wiersma. Typically, tropical birds live long lives and produce a small number of offspring that develop slowly and mature late in life. Temperate birds follow an opposite pattern; they have shorter lives and produce large numbers of offspring that develop and mature quickly.

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