Flexibility of basal metabolic rate in arctic breeding kittiwakes (Rissa tridactyla)

Information on body mass, basal metabolic rate (BMR) and body composition w ere obtained From adult female kittiwakes (Rissa tridactyla) breeding on Sv albard (79 degreesN). While body mass, BMR and body composition was stable during the incubation period, both body mass and BMR decreased significantl y during the chick-rearing period. Both whole-body and mass-specific BMR de creased during this period indicating that the reduction in BMR must be due to an altered metabolic intensity. Body composition analyses revealed that while most organs masses changed in parallel to total body mass, the liver showed a disproportional decrease. In a subsample of individuals, a signif icant relationship was also found between liver mass and BMR. The results s uggest that BMR is not a species-specific character, but rather a flexible physiological parameter. with liver mass being an important determinator.