ИСТИНА

Pied Flycatcher fledgling’s resting metabolic rate (RMR) was found to be higher in offspring of conspicuous males than in offspring of pale ones (KERIMOV, IVANKINA, 1999). Recent study showed that: (1) this relation was not influenced by variation in fledgling’s growth rates; (2) RMR of offspring was positively correlated to basal metabolic rate (BMR) of their fathers (BUSHUEV et al., 2003). To clear the nature of similarity in parent’s and offspring’s energetics we conducted two cross-fostering experiments exchanging clutches between nests. In 2003, fledgling’s RMR was positively correlated with BMR of their own fathers, and not with BMR of their foster parents, suggesting heritable variation in metabolic rate. However, next year experiment didn’t support this result. The relation between male colour type and BMR revealed during the latter year was opposite to previously found long-term dependence, according to which BMR of conspicuous males was higher than that of pale ones. Violation of the general pattern in 2004 occurred due to dramatic increase of BMR in pale males that was possibly caused by unusually cold weather during the breeding period. Thus, under certain conditions, the environmental effect of male’s BMR variation can completely mask the effect of heritability of energetic traits.