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
Long-eared owls in Eurasia have vertical striping like that of the Eurasian eagle-owl while long-eared owls in North America show a more horizontal striping like that of great horned owls. Whether these are examples of mimicry either way is unclear but it is known that both "Bubo" owls are serious predators of long-eared owls. The same discrepancy in underside streaking has also been noted in the Eurasian and American representations of the grey owl. A few other related species overlap minimally in range in Asia, mainly in east Asia and the southern reaches of the Eurasian eagle-owl’s range. Three fish owls appear to overlap in range, the brown ("Ketupa zeylonensis") in at least northern Pakistan, probably Kashmir and discontinuously in southern Turkey, the tawny ("K. flavipes") through much of eastern China and the Blakiston's fish owl in the Russian Far East, northeastern China and Hokkaido. Fish owls are distinctively different looking, possessing more scraggy ear tufts that hang to the side rather than sit erect on top of the head, generally have more uniform, brownish plumages without the contrasting darker streaking of an eagle-owl. The brown fish owl has no feathering on the tarsus or feet and the tawny has feathering only on the upper portion of the tarsi but the Blakiston’s is nearly as extensively feathered on the tarsi and feet as the eagle-owl. Tawny and brown fish owls are both slightly smaller than co-occurring Eurasian eagle-owls and Blakiston’s fish owls are similar or slightly larger than co-occurring large northern eagle-owls. Fish owls, being tied to the edges of freshwater where they hunt mainly fish and crabs, also have slightly differing, and more narrow, habitat preferences.