Dietary biology of the Eurasian eagle-owl
Throughout the western Mediterranean region, the Eurasian Eagle-Owl is something of a specialist on a single prey species: the European rabbit. The rabbit historically reached extremely high densities in Iberian scrub, i.e. more than 40 per every 1 square hectare (2471 square acres). In central Spain, up to 73.1% of the prey that were recorded for Eurasian eagle-owls, by number, can be rabbits. Where still available, they are also the main prey in Portugal and central France. However, following the devastation of the wild rabbit due to rabbit haemorrhagic disease, the local eagle-owls have frequently had to adapt to other, often smaller, prey. On the other hand, given the now much reduced numbers of rabbits, the eagle-owls still regularly select rabbits, seemingly out of proportion to their commonality. Although large mature wild rabbits commonly weigh , the eagle-owls usually hunt smaller specimens, often with an average weight around , with young rabbits usually selected in spring and summer and subadults selected in the autumn and winter. This is largely due to the behaviour of rabbits, with younger rabbits being forced to distribute following weaning, being less cautious in behaviour and occupying less primary habitat, thus being forced out of the confines of their burrows more regularly than mature adults. However, the estimated average weight of rabbits taken can be variable, reported from as little as in a study from Spain to as much as in the Netherlands.
Ural owl
The Ural owl ("Strix uralensis") is a medium-sized nocturnal owl of the genus "Strix", with up to 15 subspecies found in Europe and northern Asia.
The Ural owl is smaller than the great grey owl, and much larger than the tawny owl, which it superficially resembles. Distinguishing features apart from the size are the pale, buffish grey-brown plumage, with copious dark brown streaking on the back of the head and underparts. It has a round head with plain buffish-grey facial discs, orange-yellow bill and small black eyes. The tail is long and wedge-shaped, with dark barring on the upper tail, and the wings are rounded. Flight is direct and purposeful, recalling that of the common buzzard. Sexes are similar, with no seasonal variation. Length can range and wingspan from . Weight in males is and in females is .