Intraspecific variation in the basal metabolism of birds

For a certain biological trait to evolve (or change) through natural selection, three fundamental prerequisites must be fulfilled. Firstly, variation in the trait must necessarily be capable of influencing the inclusive fitness of individuals. Secondly, t he between-individual variation should be consistent. Thus, the variation should not merely be a product of stochastic variations, either in the environment or at the individual level. The variation should be consistent, i.e. a high and significant repeat ability should be found. Thirdly, the trait must be heritable. The present project aims at studying these aspects for a physiological parameter claimed to show adaptive variation: the basal metabolic rate (BMR). To this end, repeatability and heritability of BMR will be studied in a laboratory population of a small p asserine bird (the Zebra Finch, Taneopygia guttata), while between-population variation in BMR and the physiological basis for such variations will be studied in wild populations of another passerine bird, the Snow Bunting (Plectrophenax nivalis ):