WIERSMA, P.*; MUNOZ-GARCIA, A.; WILLIAMS, J.B.; Ohio State Univ.; Ohio State Univ.; Ohio State Univ.: Do basal metabolic rates of tropical birds suggest a low pace of life?
The effects of extrinsic factors on life-history trade-offs may result in a slow to fast �pace of life� continuum. Tropical and temperate climates are supposed to generate contrasting extremes along this continuum, with typically long lifespans, slow reproduction and low energy metabolism in the tropics. As part of an integrated, multidisciplinary project, comparing life-history parameters and physiological trades between tropical and temperate birds, we measured basal metabolic rates (BMR) of a range of tropical species. Supposedly, tropical birds have lower energetic demands as a result of a less demanding environment (e.g., favourable thermal conditions, high food availability, long breeding season). This would give rise to lower BMR values, according to the idea that BMR reflects the size of the exercise and digestive organs. We caught birds in 2004 and 2005 around Gamboa, Panama, mostly in low-land, secondary rainforest. A first comparison between our data and published allometric relationships did not reveal a difference between tropical and temperate bird species lighter than 138 g. In addition, we measured Total Evaporative Water Loss (TEWL) and body temperature (Tb) as components of heat loss and BMR. Furthermore, variation in BMR will be linked to variation in habitat preference and life-styles (as defined by, e.g., diet and foraging mode).
