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.
Dietary biology of the Eurasian eagle-owl
Jirds, jerboas, gerbils and hamsters, particular the genera "Allactaga", "Ellobius", "Gerbillus", "Meriones", and "Pygeretmus", start to become noticeable in the diet in the more arid portions of this species’ range, i.e. from Asia Minor to the Middle East and Central Asia. Relatively large species such as Tristram's jird ("Meriones tristrami") and the Euphrates jerboa ("Allactaga euphratica") are often amongst the more prominent species to be hunted. In western Kazakhstan, the primary foods are the great jerboa ("Allactaga major") and northern mole vole ("Ellobius talpinus") while on the Buzachi and Mangyshlak Peninsulas of the Kazakh Caspian Sea, the primary foods were the Libyan jird ("Meriones libycus"), great gerbil ("Rhombomys opimus") and small five-toed jerboa ("Allactaga elater"). All told, in the peninsular Kazakh regions of the Caspian Sea, jirds, jerboas and gerbils made up about 92% of the food. In the Tibetan Plateau of China, the tundra vole ("Microtus oeconomus") is the leading prey species, making up 53.1% of the prey. In Mongolia, two rather small rodents, the Mongolian five-toed jerboa ("Allactaga sibirica"), at 23.6% of the prey, and the Campbell's dwarf hamster ("Phodopus campbelli"), at 14.5% of the prey, make up a majority of the prey by number. In the Transbaikal, the Chinese striped hamster ("Cricetulus barabensis") was the main prey species, making up 43.8% of the diet.
What all primary rodent prey species share is that they are either nocturnal or crepuscular and are often common to abundant in openings of woods and rocky environments. The reason Eurasian eagle-owls take rats, which associate rather closely with humans, much more regularly than they take house mice ("Mus musculus") is not their larger size (many other rodents regularly taken by eagle-owls are as small or smaller than a house mouse) but the rat's ability to flourish along the edges of crop fields, refuse dumps, roadsides and abandoned buildings and fields, whereas the mice are more closely tied to active human habitations. A single refuse dump can host several thousand rats and eagle-owl territories that include dumps can locally expect higher productivity due to the abundance of this food source. Squirrels are readily predated but, being diurnal, are largely unavailable to this and other owls. When they are captured, it is presumably around dawn or dusk from their tree hole, in species such as the widespread red squirrel ("Sciurus vulgaris"), or burrow entrance, in the case of ground squirrels, most regularly recorded as prey in Asia Minor and the Central Asia. A few specimens of the woolly flying squirrels ("Eupetaurus cinereus"), the largest of the world's flying squirrels and one of the rarest, were the only identified foods for Eurasian eagle-owls in northern Pakistan alongside some European hares. Although not common in the diet, a few species of marmot have been taken and may be an important aspect of the prey biomass. In Europe, adult-sized alpine marmots, ("Marmota marmota") have been killed. However, the average weight of Tarbagan marmots ("Marmota sibirica") taken in Mongolia was only and that of alpine marmots in Engadin, Switzerland was only . These obviously comprising young marmots as adults have average weights from , from spring low weights to pre-hibernation weights during autumn hypophagia. Other than marmots, the largest rodent known to be hunted by Eurasian eagle-owls is the introduced aquatic rodents, the muskrat ("Ondatra zibethica"), which in one study estimated to average when taken, and the nutria ("Myocastor coypus"), equal in size to the large marmots.