Seasonal phenotypic flexibility in body mass, basal thermogenesis, and tissue oxidative capacity in the male Silky Starling (Sturnus sericeus)

Background Acclimatization to winter conditions is an essential prerequisite for the survival of small birds in the northern temperate zone. Changes in photoperiod, ambient temperature and food availability trigger seasonal physiological and behavioral acclimatization in many passerines. Seasonal trends in metabolic parameters are well known in avian populations from temperate environments; however, the physiological and biochemical mechanisms underlying these trends are incompletely understood. In this study, we used an integrative approach to measure variation in the thermogenic properties of the male Silky Starling (Sturnus sericeus) at different levels or organization, from the whole organism to the biochemical. We measured body mass (M b), basal metabolic rate (BMR), energy budget, the mass of selected internal organs, state 4 respiration and cytochrome c oxidase (COX) activity in the heart, liver and muscle.