Eurasian eagle-owl
The Eurasian eagle-owl is a member of the genus "Bubo", which may include either 22 or 25 extant species. Almost all the larger owl species in the world today are included in "Bubo". Based on an extensive fossil record and a central distribution of extant species on that continent, the "Bubo" appears to have evolved into existence in Africa, although early radiations seem to branch from southern Asia as well. Two genera belonging to the scops owls complex, the giant scops owls ("Otus gurneyi") found in Asia and the "Ptilopsis" or the white-faced scops owl found in Africa, although firmly ensconced in the scops owl group, appear to share some characteristics with the eagle-owls. The "Strix" is also related to the "Bubo" and is considered a "sister complex", with the "Pulsatrix" possibly being intermediate between the two. The Eurasian eagle-owl appears to represent an expansion of the genus "Bubo" into the Eurasian continent. A few of the other species of "Bubo" seem to have been derived from the Eurasian eagle-owl, making it a "paraspecies", or they at least share a relatively recent common ancestor. The Pharaoh eagle-owl, distributed in the Arabian Peninsula and sections of the Sahara Desert through North Africa where rocky outcrops are found, was until recently considered a subspecies of the Eurasian eagle-owl. It appears that the Pharaoh eagle-owl differs about 3.8% in mitochondrial DNA from the Eurasian eagle-owl, well past the minimum genetic difference to differentiate species of 1.5%. Smaller and paler than Eurasian eagle-owls, the Pharaoh can also be considered a distinct species largely due to its higher pitched and more descending call and the observation that Eurasian eagle-owls formerly found in Morocco ("B. b. hispanus") apparently did not breed with the co-existing Pharaoh eagle-owls. On the contrary, the race still found together with the Pharaoh eagle-owl in the wild ("B. b. interpositus") in the central Middle East has been found to interbreed in the wild with the Pharaoh eagle-owl, although genetical materials have indicated "interpositus" may itself be a distinct species from the Eurasian eagle-owl, as it differs from the nominate subspecies of the Eurasian eagle-owl by 2.8% in mitochondrial DNA. The Indian eagle-owl was also considered a subspecies of Eurasian eagle-owl until recently, but its smaller size, distinct voice (more clipped and high-pitched than Eurasians), and the fact that it is largely allopatric in distribution (filling out the Indian subcontinent) with other Eurasian eagle-owl races has led to it being considered a distinct species. The mitochondrial DNA of the Indian species also appears considerably distinct from the Eurasian species. The Cape eagle-owl ("B. capensis") appears to represent a return of this genetic line back into the African continent, where it leads a lifestyle similar to northern eagle-owls albeit far to the south. Another offshoot of the northern "Bubo" group is the snowy owl. It appears to have separated from other "Bubo" at least 4 million years ago.
Eurasian eagle-owl
The male selects breeding sites and advertises their potential to the female by flying to them and kneading out a small depression (if soil is present) and making staccato notes and clucking noises. Several potential sites may be presented, with the female selecting one. Like all owls, Eurasian eagle-owls do not build nests or add material but nest on the surface or material already present. Eurasian eagle-owls normally nest on rocks or boulders, most often utilizing cliff ledges and steep slopes, as well as crevices, gullies, holes or caves. Rocky areas that also prove concealing woodlots as well as, for hunting purposes, that border river valleys and grassy scrubland may be especially attractive. If only low rubble is present, they will nest on the ground between rocks. Often, in more densely forested areas, they’ve been recorded nesting on the ground, often among roots of trees, under large bushes and under fallen tree trunks. Steep slopes with dense vegetation are preferred if nesting on the ground, although some ground nests are surprisingly exposed or in flat spots such as in open spots of the taiga, steppe, ledges of river banks and between wide tree trunks. All Eurasian eagle-owl nests in the largely forested Altai Krai region of Russia were found to be on the ground, usually at the base of pines. This species does not often use other bird’s nests as does the great horned owl, which often prefers nests built by other animals over any other nesting site. The Eurasian eagle-owl has been recorded in singular cases using nests built by common buzzards ("Buteo buteo"), golden eagle, greater spotted ("Clanga clanga") and white-tailed eagles ("Haliaeetus albicilla"), common ravens ("Corvus corax") and black storks ("Ciconia nigra"). Among the eagle-owls of the fairly heavily wooded wildlands of Belarus, they more commonly utilize nests built by other birds than most eagle-owls, i.e. stork or accipitrid nests, but a majority of nests are still located on the ground. This is contrary to the indication that ground nests are selected only if rocky areas or other bird nests are unavailable, as many will utilize ground nests even where large bird nests seem to be accessible. Tree holes being used for nesting sites are even more rarely recorded than nests constructed by other birds. While it may be assumed that the eagle-owl is too large to utilize tree hollows, when other large species like the great grey owl have never been recorded nesting in one, the even more robust Blakiston's fish owl nests exclusively in cavernous hollows. The Eurasian eagle-owl often uses the same nest site year after year.
In Engadin, Switzerland, the male eagle-owl hunts until the young are 4 to 5 weeks old and the female spends all her time brooding at the nest. After this point, the female gradually resumes hunting from both herself and the young and thus provides a greater range of food for the young. While it may seem contrary to the species’ highly territorial nature, there is one verified cases of polygamy in Germany, with a male apparently mating with two females, and cooperative brooding in Spain, with a third adult of undetermined sex helping a breeding pair care for the chicks. The response of Eurasian eagle-owls to humans approaching at the nest is quite variable. The species is often rather less aggressive than some other owls, including related species like the spot-bellied eagle-, great horned and snowy owls, many of the northern "Strix" species and even some rather smaller owl species, which often fearlessly attack any person found to be nearing their nests. Occasionally, if a person climbs to an active nest, the adult female eagle-owl will do a distraction display, in which they feign an injury. This is an uncommon behaviour in most owls and most often associated with small birds trying to falsely drawl the attention of potential predators away from their offspring. More commonly, the female flies off and abandons her nest temporarily, leaving the eggs or small nestlings exposed, when a human approaches it. Occasionally, if cornered both adults and nestlings will do an elaborate threat display, also rare in owls in general, in which the eagle-owls raise their wings into a semi-circle and puff up their feathers, followed by a snapping of their bills. Apparently eagle-owls of uncertain and probably exotic origin in Britain are likely to react aggressively to humans approaching the nest. Also, aggressive encounters involving eagle-owls around their nest, despite being historically rare, apparently have increased in recent decades in Scandinavia. The discrepancy of aggressiveness at the nest between the Eurasian eagle-owl and its Nearctic counterpart may be correlated to variation in the extent of nest predation that the species endured during the evolutionary process.