ИСТИНА

Basal metabolic rate (BMR) is a widely examined energetic trait, which is often considered to be an indicator of competitive ability of an animal. Several studies have shown that BMR is a very flexible physiological trait and can vary under the influence of many endogenous and environmental factors. To test whether BMR could be a characteristic feature of an individual, we estimated the repeatability of mass-specific BMR in natural population of Pied Flycatcher (Ficedula hypoleuca) in Moscow region (55º44´ N, 36º51´ E) using our long-term (1992–2007) data-set on Pied Flycatchers. In some years BMR of the same Pied Flycatcher males was measured twice within the reproductive season: 1) shortly after arrival to the breeding area in late April or early May, when males perform advertising behaviour; 2) in the middle of the chick-rearing period in June. Males showed highly significant BMR increase from advertising period until chick-rearing period. As a consequence, BMR repeatability (R) within the same year did not significantly differ from zero (n=81). However, repeatability estimate of BMR measured in the same period of a season was R=0.37±0.09 between consecutive years (n=79), R=0.60±0.15 for 2 years interval (n=25) and R=0.85±0.14 for 3 years interval (n=5). This is a first report of BMR repeatability in free-living animals over a period of more than one year. The repeatability value is often regarded as an upper estimate of heritability. Therefore, our findings of stable intra-individual variation of BMR during such considerable time intervals assume the potential for direct selection on this energetic trait.