Bech, C., I. Langseth and G.W. Gabrielsen (1999). Repeatability of basal metabolism in breeding female kittiwakes Rissa tridactyla. Proc. R. Soc. Lond. B 266: 2161-2167.

We studied Kittiwakes (Rissa tridactyla) breeding near Ny-Ålesund (79°N, 12°E) on Svalbard. In 1997, the basal metabolic rates (BMR) of 17 breeding females were measured during the incubation and the chick-rearing period. The mean body mass of the Kittiwakes decreased, significantly, by 10%, between the incubation period and the chick-rearing period. At the same time, both whole-body and mass-specific BMR decreased significantly. There was a positive and significant relationship between the BMR-residuals from the incubation period and those from the chick-rearing period. Thus, the BMR of incubating female Kittiwakes was a significant predictor of their BMR during the chick rearing period. New BMR data were collected in 1998 from 10 of these females, measured about chick hatching date. Repeatability values were calculated using either a) data for eight individuals for which three BMR measurements existed or b) all the data from both years, yielding significant repeatabilities of 0.52 and 0.35, respectively. These values indicate that between 48 and 65% of the observed variation in BMR is due to intra-individual variability, while between-individual variability accounts for 35-52% of the variation in the BMR. This is the first report of a significant repeatability of the BMR of an endothermic organism across an elapsed time of more than a day.