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.
Northern goshawk
Outside of the accipitrid group, heavy predation on different varieties of raptorial birds by northern goshawks can continue unabated. Many types of owl are taken and in Europe, the northern goshawk is the second most prolific predator of owls behind the Eurasian eagle owl ("Bubo bubo"). In Bavaria, Germany, the long-eared owl ("Asio otus") was the second most common prey species for nesting goshawks. In the Białowieża Forest of Poland, fairly high numbers of the tawny owl ("Strix alucco") were taken. In all, some 18 species of owl have been recorded in the diet, ranging in size from the Eurasian ("Glaucidium passerinum") and northern pygmy owls ("Glaucidium gnoma") at and , respectively, to all the large northern "Strix" owls including adults and even the great horned owl. Whether adults have ever been killed as prey though is unknown but goshawks have been known to kill great horned owls that they've found near their nests. In addition, about eight species of falcon have been identified in the foods of goshawks. Adult falcons of small species such as kestrels and merlins ("Falco columbarius") can be overpowered quite easily if they can manage to surprise the prey. Larger falcons have turned up in the diet as well, including the prairie falcon ("Falco mexicanus") and the saker falcon ("Falco cherrug"), although possible only nestlings of these species. Brief aerial skirmishes between goshawks and peregrine falcons ("Falco peregrinus") have been described but neither species is known to have killed one another in the wild. In Schleswig-Holstein, Germany, at least four small passerines species were recorded as nesting close to active goshawk nest, due to the incidental shelter that the fierce goshawks inadvertently provides from smaller raptors which are their main predators. Such raptors, including Eurasian kestrels, Eurasian sparrowhawks and long-eared owls, not only avoid goshawk activity where possible but also were found to have lower nest productivity any time they nested relatively close to goshawks per the study. A similar phenomenon, with goshawks inadvertently providing shelter to small passerines, has been recorded in North America as well.
Competition for northern goshawks can also come from mammalian carnivores. Martens, and to a lesser extent other weasels, are presumably one of their more major competitors as their diet often consists of similar prey primarily during spring and summer, tree squirrels and woodland birds, but little has been studied in terms of how the two types of predator effect each other. Most recorded interactions have been predatory, as the goshawk has been recorded preying on a dozen species, from the least weasel ("Mustela nivalis") to the stone marten ("Martes foina"). Northern goshawks have also been recorded as feeding on much bigger predators such as the red fox ("Vulpes vulpes"), the raccoon dog ("Nyctereutes procyonoides") and the striped skunk ("Mephitis mephitis"), but it is not clear whether these were actual kills, as many may be encountered as already dead carrion. Domestic carnivores are sometimes eaten, including dogs and cats, the latter of which has reportedly been taken alive by goshawks. The red fox is a surprisingly considerable competitor for resources with northern goshawks. It was found in Norway that goshawk numbers were higher when voles were at peak numbers, not due to voles as a food source but because foxes were more likely to eat the rodents and ignore grouse, whereas during low vole numbers the foxes are more likely to compete with goshawks over grouse as prey. A decrease of the fox population of Norway due to sarcoptic mange was found result in an increase of grouse numbers and, in turn, northern goshawks. In some areas, red foxes have been found to steal up to half of the goshawks’ kills.