The distribution of the Great Grey Owl is holarctic, i.e. the species occurs in both Eurasia and North America. It is estimated that about 600 pairs of Great Grey Owls breed in Finland. The Great Grey Owl is specialized in the hunting of voles, so the variations in the population of the species follow the variation of vole populations. The Great Grey Owl is large and can break a snow cover that could carry the weight of a human as it attacks a vole.
In owls, the female is usually larger than the male. A Great Grey Owl male usually weighs less than one kilogram and a female weighs up to two kilograms. The hoots of a Great Grey Owl carry only a few hundred meters. The species usually breeds in old nests of birds of prey but breeding in rotting trees is also relatively common. From time to time, the owl also accepts a nest box. If you happen to walk by a Great Grey Owl’s nest, be vigilant as the species defends its nest aggressively. Most of the adult Great Grey Owls in the Nordic countries are sedentary, but young individuals sometimes move more after the voles. According to Finnish ringing data, the longest transitions have been over 900 kilometres. Occasionally, there may be lot of Great Grey Owls on roadside fields, which makes them particularly vulnerable to traffic deaths. According to Finnish ringing data, the age record of the Great Grey Owl is 16 years.
Text: Jukka Jokimäki & Marja-Liisa Kaisanlahti-Jokimäki
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