The Eurasian eagle-owl is one of the largest living species of owl. This bird has distinctive ear tufts, with upper parts that are brown-black to tawny-buff to pale creamy gray. A narrow buff band, freckled with brown or buff, often runs up from the base of the bill, above the inner part of the eye and along the inner edge of the black-brown ear tufts. The facial disc is tawny-buff, speckled with black-brown, so densely on the outer edge of the disc as to form a "frame" around the face. The chin and throat are white with a brownish central streak. The feathers of the upper breast generally have brownish-black centers and reddish-brown edges except for the central ones which have white edges. The chin and throat may appear white continuing down the center of the upper breast. The lower breast and belly feathers are creamy-brown to tawny buff to off-white with a variable amount of fine dark wavy barring, on a tawny-buff ground color. The tail is tawny-buff, mottled dark grey-brown with about six black-brown bars. The bill and feet are black. The eyes are most often orange in color.
Eurasian eagle-owls are found in much of Europe, Asia, and the Middle East. These birds live in many habitats but mostly in mountain regions, coniferous forests, steppes, and other relatively remote places. They are often found in areas where cliffs and ravines are surrounded by a scattering of trees and bushes. Grassland areas such as alpine meadows or desert-like steppe can also host them so long as they have the cover and protection of rocky areas. Eurasian eagle-owls can also be found living in mountainous areas and at sea-level and may nest amongst rocky sea cliffs.
Eurasian eagle-owls are largely nocturnal, with their activity focused in the first few hours after sunset and the last few hours before sunrise. During the day they may roost singly or in pairs in trees or in rock crevices. Eurasian eagle-owls communicate with the help of vocalizations that are used at different times. They are mainly heard during the colder months from late fall through winter; vocal activity in October-December mainly has territorial purposes and from January to February being primarily oriented towards courtship and mating purposes. The territorial song, which can be heard at a great distance, is a deep resonant ooh-hu with emphasis on the first syllable for the male, and a more high-pitched and slightly more drawn-out uh-hu for the female. A mated pair may often perform an antiphonal duet. Other calls include a rather faint, laughter-like OO-OO-oo and a harsh kveck-kveck. Intruding eagle-owls and other potential dangers may be met with a "terrifying", extremely loud hooo. Annoyance at close quarters is expressed by bill-clicking and cat-like spitting, and a defensive posture involves lowering the head, ruffling the back feathers, fanning the tail and spreading the wings.
Eurasian eagle-owls are monogamous and often mate for life. Pairs usually engage in courtship rituals annually, most likely to re-affirm pair bonds. Calling for the purposes of courtship starts in January and February. During these courtship rituals males tend to bow and hoot loudly. Courtship may involve bouts of "duetting", with the male sitting upright and the female bowing as she calls. There may also be mutual bowing, billing and fondling. The male selects breeding sites and shows them to the female by flying to them and kneading out a small depression (if soil is present) and making staccato notes and clucking noises. The female selects one breeding site. Eurasian eagle-owls do not build nests or add material but nest on the surface or material already present. They normally nest on rocks or boulders, most often utilizing cliff ledges and steep slopes, as well as crevices, gullies, holes or caves. Pairs often use the same nest site year after year. Laying generally begins in late winter. The clutch size is usually 1-2, rarely 3 to 4 eggs. The eggs are laid at intervals of three days and are incubated only by the female. During the incubation period, the male brings food at the nest. The first egg hatches after 31 to 36 days of incubation. Like all owls that nest in the open, the downy owlets are often a mottled grey with some white and buff, which provides camouflage. They open their eyes at 4 days of age. The owlets grow rapidly and are able to consume small prey whole when they are three weeks old. They can walk well at five weeks of age and by seven weeks are taking short flights. Normally, they are cared for 20-24 weeks and become independent between September and November. They become reproductively mature and are ready to breed at 2 to 3 years of age.
The main threat to Eurasian eagle-owls is human activity. These birds are highly sensitive to disturbance, particularly during incubation, which may cause adults to abandon eggs and even small young. Eurasian eagle-owls also suffer from human persecution and poisoning, widespread urbanization, as well as collisions with vehicles and wires.
According to the IUCN Red List, the total Eurasian eagle-owl population size is around 100,000-499,999 mature individuals. In Europe, the breeding population is estimated to number 18,500-30,300 pairs, which equates to 36,900-60,600 mature individuals. Currently, Eurasian eagle-owls are classified as Least Concern (LC) on the IUCN Red List, but their numbers today are decreasing.
Due to preying upon various small mammals, Eurasian eagle-owls control the populations of these species; this way they prevent a possible spread of disease throughout the range and maintain the health of the ecosystem.