Subcutaneous fat accumulation in Norwegian owls and raptors

Abstract

The mean subcutaneous fat deposition (MFS) found in dead diurnal raptors and owls collected in Norway in 1987-92 was compared to detect possible overall and intra- and interspecific seasonal differences. In general, the relative fat deposition rate was correlated with body size (P < 0.001), and was highest in winter (P = 0.01) and in females (P = 0.02) . After correcting for the size effect, species-specific differences were still present (P = 0.000), but the effect of sex disappeared (P = 0.34) . We propose that the relative rate of fat deposition in northern Palaearctic owls and raptors reflects adaptations to resist starvation balanced against the demands for high agility and low flying costs. This trade-off probably varies between breeding and non-breeding seasons, sexes, and species with different migratory and hunting habits .