ИСТИНА

The relationship between metabolic rate (MR) and body mass (M) is expressed by the allometric equation MR=a*M^b, where a is the allometric coefficient and b is the scaling exponent (the slope in a log-log plot). Debates about variation in the scaling of metabolic rate with body mass have been going on for more than half a century, although it has been widely accepted that the scaling exponent is 3/4 ("3/4-power law" or Kleiber's law). Most studies of allometry in metabolic rates have been done on an interspecific level, because large body mass range is required for reliable regression analysis. Intraspecific metabolic scaling is usually reported for animals with long-term growth (such as invertebrates of different taxa, fishes, reptiles). Birds as a class are the most unstudied group of vertebrates with respect to intraspecific scaling. Using our long-term data we overcame the problem of narrow body mass range by means of large sample sizes. We studied the relationship between body mass and whole-organism nighttime resting metabolic rate in two separated Pied Flycatcher (Ficedula hypoleuca) populations and one Great Tit (Parus major) population. All estimates were highly significant. The scaling exponent was close to unity (b=1.11, SE=0.08, n=1035 in Moscow Region, 1992—2010; b=0.95, SE=0.14, n=348 in Tomsk Region, 2008—2009) in adult Pied Flycatchers, close to 2/3 (b=0.67, SE=0.04, n=953 in Moscow Region, 2000—2005) in 13—15 day old Pied Flycatcher chicks, and between 2/3 and 3/4 (b=0.71, SE=0.04, n=792 in Moscow Region, 1992—2000) in adult Great Tits. The result is in contrast with estimates for other species: all studies in nestlings found the scaling exponent to be close to unity. Different intrinsic and extrinsic factors (sex, age, moult, Drost’s colour type, period, season, ambient temperature) were taken into account. Ecological consequences of different scaling exponents in the studied species are discussed.