Metabolic Rates and Life Histories in Birds

Abstract
It has been argued that metabolic rate is an important variable in the evolution of life-history variation: high metabolic rates relative to body size are associated with high fecundity and short life-spans. We present here the first analysis in birds of the relationship between life-history variation and metabolic rate, controlling for the effects of body size. Our results from 325 species belonging to 18 different orders do not support the prediction that metabolic rate is positively correlated with the rate of offspring production and neonatal growth. Further, no evidence is found for the predicted negative association between metabolic rate and life-span. We conclude that there is no empirical evidence, based on the available data, that metabolic rate differences are associated with life-history variation in birds independently of body weight and phylogenetic association.