ИСТИНА

The research was conducted in the north of Moscow Region (Russia) in 2001–2014. Mean clutch size of Long-eared Owls annually varied from 4.0 to 6.5 eggs, averaged 5.0±0.2 eggs over all years. The number of eggs in successful (5.2±0.3) and unsuccessful (4.3±0.3) nests differed significantly (Z=2.04; p≤0.05). The clutch size negatively correlated with the nesting start date (rs= –0.58; p≤0.05) and positively – with the rodent abundance in spring (rs=0.55; p=0.08). The annual fecundity of owls reached 1.1-4.7 chiсks per nest, averaged 2.9±0.4 chicks per nest over all years. Analysing only successful nests, i.e. with at least one nestling leaving the nest, the fecundity was higher (3.3±0.3) with interannual variation from 2.3 to 5.4 chicks per nest. The average number of chicks from successful nests positively correlated with the average temperature in May, when most fledglings leave their nests. The average survival rate of fledglings (69±4%) negatively correlated with the amount of precipitation in June (rs=–0.79; p≤0.05). The owls breeding success varied from 0 to 77% (averaged 42±8%) and negatively correlated with the temperature of the second half of April (rs=–0.56; p≤0.05). It could be explained by more intensive incubation which among other things reduced nests predation.