Instruct: Given a question, retrieve relevant documents that answer the question.
Query: Can a Eurasian eagle-owl kill a rabbit?
In the Iberian peninsula, the Eurasian eagle-owl is part of a complex guild of predators that have evolved to survive mostly on European rabbits. Among this guild, golden eagles (Aquila chrysaetos) were recorded per one study to rely on rabbits for 40% of the diet, the eagle-owl for 49% of the diet, the Spanish imperial eagle (Aquila adalberti) for 50% of the diet, the Bonelli's eagle (Aquila fasciata) for 61% of the diet and the Iberian lynx (Lynx pardinus) for 79% of the diet.[2] Elsewhere, the Spanish imperial eagle and eagle-owl are considered to outflank the golden and even the Bonelli's eagle as the most specialized avian predator of rabbits in the Iberian region.[13] Other predators, such as common buzzard (Buteo buteo), northern goshawk (Accipiter gentilis) black kite (Milvus migrans) Iberian wildcat (Felis silvestris tartessia), red fox, stone marten (Martes foina) and introduced Egyptian mongoose also prey heavily on rabbits in Spain, but are more generalized and less reliant than the above predators.[117][118][119][120] All these powerful predators do not generally compete directly for food but conflicts may ensue over the rights to territories and nesting sites amongst the birds. Being nocturnal in activity, however, the Eurasian eagle-owl does not tend to compete as directly as do the three eagle species and even these are discreetly segregated by habitat preferences, the goldens preferring open, steep cliffs, the Bonelli's favoring densely vegetated areas mixed with rocky spots and the imperial favoring relatively flat open woodlands.[121] Among these eagles, the golden eagle tends to have the most similar habitat preferences to the Eurasian eagle-owl and across a broad band of overlapping distribution, the two are considered nearly ecological equivalents by day and night. However, good-sized female golden eagles are up to twice as heavy as an average eagle-owl, so seem to have a considerable advantage in size and power.[2] Conversely, to support their large size and large territory needs, the golden eagle cannot survive on small and diverse prey nearly as successfully as the eagle-owl. Among the Iberian peninsula rabbit-eating guild, the species with wider ranges, the eagle-owl and the golden and Bonelli's eagles, have had some degree of success living off of alternate prey following the devastation of the rabbit population due to rabbit haemorrhagic disease. The two rabbit predators endemic to Iberia, the Iberian lynx and Spanish imperial eagle, have been devastated by the reduction and other causes and both are threatened species today.[122][123][124][125]
The great size, bulky, barrel-shaped build, erect ear tufts and orange eyes render this as a distinctive species. Other than general morphology, the above features differ markedly from those of two of the next largest subarctic owl species in Europe and western Asia, which are the great grey owl and the greyish to chocolate-brown Ural owl (Strix uralensis), both of which have no ear tufts and have a distinctly rounded head, rather than the blocky shape of the eagle-owl’s head.[4][14] The snowy owl is obviously distinctive from most eagle-owls, but during winter the palest Eurasian eagle-owl race (B. b. sibiricus) can appear off-white. Nevertheless, the latter is still distinctively an ear-tufted Eurasian eagle-owl and lacks the pure white background colour and variable black spotting of the slightly smaller species (which has relatively tiny, vestigial ear tufts that have only been observed to have flared on rare occasions).[5][14] The long-eared owl has a somewhat similar plumage to the eagle-owl but is considerably smaller (an average female eagle-owl may be twice as long and ten times heavier than an average long-eared owl).[28]
In Spain, long-term governmental protection of the Eurasian eagle-owl seems to have no positive effect on reducing the persecution of eagle-owls. Therefore, Spanish conservationists have recommended to boost education and stewardship programs in order to protect eagle-owls from direct killing by local residents.[98]
Discreet habitat preferences may coincidentally spare many owls, as owls from the genera Strix, Glaucidium, Aegolius and the 320g (11oz) northern hawk-owl (Surnia ulula) tend to restrict both nesting and their hunting forays to more enclosed areas of woodland than habitats inhabited by the eagle-owls.[112][132] Meanwhile, Asio, Otus, Athene and barn owls owls tend to hunt in more open habitats than the edges favored by eagle-owls.[2] However, habitat preferences are never enough to spare any of these genera from predation by the great eagle-owl. In the Italian Alps, despite differing habitat preferences and partially overlapping prey, several tawny owls were killed by eagle-owls.[133] Woodland nesting owl species tend to nest in tree hollows, many of which are too small for an eagle-owl to access, so are somewhat less likely to be picked off at their nests. Open-country owls that tend to nest in open-access nesting sites like short-eared owls and little owls may be somewhat more vulnerable at the nest. The great numbers of long-eared owls taken, since it often nest in dense, protective thickets, are probably adult or immature owls attempting to hunt. In Europe, Eurasian eagle-owls are generally the only owls to regularly nest in rocky habitats. This is not the case in arid desert-like regions, where limited nesting options frequently force diverse owls to use rocky areas as nesting sites.[3][112] However, the cliffs and other rocky areas preferred by Eurasian eagle-owls are also utilized by several species of diurnal raptor in Eurasia. In Spain, golden eagles, Bonelli's eagles and peregrine falcons (Falco peregrinus) most often nest on cliffs. Large scavenging birds such as cinereous vultures (Aegypius monachus), bearded vultures (Gypaetus barbatus), Eurasian griffons (Gyps fulvus), Egyptian vulture (Neophron percnopterus) and common ravens also often nests on the same Iberian cliffs. While the two eagles nested at great distances from one another (they are known to be territorial towards each other), the eagle-owl nesting within 2 to 3km (1.2 to 1.9mi) of the other species. In these cliff nests, the only considerable predatory interaction was the eagle-owls appearing to predate the peregrine falcons.[134] In the Tibetan Plateau, upland buzzards (Buteo hemilasius) also seem to favor similar habitats and both the eagle-owl and buzzard take similar prey there.[50] In general, the eagle-owl can nest closer to diurnal raptors because, as a nocturnal animal, it will not actively compete for territories as it would with other members of its own species.[2]
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.[6] 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.[4][14]
Equally or even more so than the great horned owl, the Eurasian eagle-owl is a threat to any smaller type of raptor it encounters, whether other owls or diurnal birds of prey. All told, more than 20 species of accipitrid, 15 species of owl and 9 species of falcon have been found amongst their prey. The Eurasian eagle-owl is the primary predator of other birds of prey throughout Eurasia, not even the prolific raptor-killing northern goshawk (Accipiter gentilis) equals the sheer number of raptors taken.[79][126][127] Up to 6% of the overall food by number and 36% by prey biomass for Eurasian eagle-owls can be comprised by other raptorial birds.[2][79] The primary raptorial prey taken by Eurasian eagle-owls in Europe are two species: the 300g (11oz) long-eared owl and the 776g (1.711lb) common buzzard.[2][95] Both are taken in such large numbers that they rank in the top five most regularly hunted bird species in Europe. In Luxembourg, the long-eared owl and common buzzard were the fourth and fifth most regularly hunted prey species.[96] Other high rankings have included the long-eared owl being the fourth most regular prey species in Bavaria and the buzzard being the third most regular prey species in a study from the Czech Republic.[75][128] While migrating, long-eared owls appear to select areas to move through partially based on whether or not eagle-owls are detected, thus eagle-owls have a very serious influence on the behaviour of this prey.[15] Despite the large numbers taken of both of these, the more scarce eagle-owl does not seem to have a serious deleterious effect on their overall population, especially compared to anthropogenic factors.[2][126]
In the lower Himalayas of northern Pakistan and Jammu and Kashmir, along with the brown fish owl, the Eurasian eagle-owl at the limit of its distribution may co-exist with at least two to three other eagle-owls.[6] One of these, the dusky eagle-owl (B. coromandus) is smaller, with more uniform tan-brownish plumage, untidy uniform light streaking rather than the Eurasian’s dark streaking below and an even less well-defined facial disc. The dusky is usually found in slightly more enclosed woodland areas than Eurasian eagle-owls.[4][14] Another is possibly the spot-bellied eagle-owl (Bubo nipalensis), which is strikingly different looking, with stark brown plumage, rather than the warm hues typical of the Eurasian, bold spotting on a whitish background on the belly, and somewhat askew ear tufts that are bold white with light brown crossbars on the front. It is possible that both species occur in some parts of the Himalayan foothills but they are not currently verified to occur in the same area, in part because of the spot-bellied’s preference for dense, primary forest.[14] Most similar, with basically the same habitat preferences and the only one verified to co-occur with the Eurasian eagle-owls of the race B. b. turcomanus in Kashmir is the Indian eagle-owl (B. bengalensis).[4] The Indian species is smaller with a bolder blackish facial disc border, more rounded and relatively smaller wings and partially unfeathered toes. Far to the west, the pharaoh eagle-owl (B. ascalaphus) also seemingly overlaps in range with the Eurasian, in at least the country of Jordan. Although also relatively similar to the Eurasian eagle-owl, the pharaoh is distinguished by its smaller size, paler, more washed-out plumage and the diminished size of its ear-tufts.[4][14]
The diet is generally more diverse than any other co-existing owl but often focuses predominantly on a particular range of prey species, with two to four species often making up the majority of the diet.[15] Studies conducted over the course of years has shown that the regional diet often changes dramatically from year to year. This is partially driven by the cyclical population trends of much of their prey as well as by habitat changes, which are often due to human activities.[2][15] The primary prey species varies by region but is comprised mainly by small mammals such as voles, rats, mice, rabbits and hares.[3] In Europe, the five main prey species are, in order of extent of reporting and numeric abundance in dietary studies: the brown rat (Rattus norvegius), which has now occupied edge habitats (although generally associated with man) in almost every part of Europe excluding the colder north; the common vole (Microtus arvalis), often the most abundant native, small mammal in wild portions of Europe;[16] the European hedgehog (Erinaceus concolor), which occupies wooded edges across western Europe alongside the eagle-owls; the European water vole (Arvicola amphibius), a unique, large vole occupying the wetland edges often hunted by eagle-owls; and the European rabbit (Oryctolagus cuniculus), which has a very close relationship with the eagle-owls found throughout the Iberian Peninsula and the massifs of France.[2][17][18] As the distribution of the Eurasian eagle-owls moves west (and south), the primarily prey species gradually change but often continues to be dominated in number by small rodents and in biomass by slightly larger mammals such as hedgehogs and hares and rabbits.[2][18]
Although found in the largest numbers in areas sparsely populated by humans, farmland is sometimes inhabited and they even have been observed living in park-like settings within European cities.[14] Since 2005, at least five pairs have nested in Helsinki.[62] This is due in part to feral European rabbits (Oryctolagus cuniculus) having recently populated the Helsinki area, originally from pet rabbits released to the wild. The number is expected to increase due to the growth of the European rabbit population in Helsinki. European hares (Lepus europaeus), the often preferred prey species by biomass of the eagle-owls in their natural habitat, live only in rural areas of Finland, not in the city centre. In June 2007, an eagle-owl nicknamed 'Bubi' landed in the crowded Helsinki Olympic Stadium during the European Football Championship qualification match between Finland and Belgium. The match was interrupted for six minutes.[63] After tiring of the match, following Jonathan Johansson's opening goal for Finland, the bird left the scene.[63] Finland's national football team have had the nickname Huuhkajat (Finnish for "Eurasian eagle-owls") ever since. The owl was named "Helsinki Citizen of the Year" in December 2007.[64]
Even those near the northern limits of their range, where winters are harsh and likely to bear little in food, the eagle-owl does not leave its native range. There are cases from Russia of Eurasian eagle-owls moving south for the winter, as the icebound, infamously harsh climate there is too severe even for these hardy birds and their prey. Similarly, Eurasian eagle-owls living in the Tibetan highlands and Himalayas may in some cases vacate their normal territories when winter hits and move south. Even in those two examples, there is no evidence of consistent, annual migration by Eurasian eagle-owls and the birds may eke out a living on their normal territories even in the sparsest times.[5][6]
The Eurasian eagle-owl is a very large bird, smaller than the golden eagle (Aquila chrysaetos) but larger than the snowy owl, despite some overlap in size with both species. It is sometimes referred to as the world's largest owl,[4][11] although Blakiston's fish owl (B. blakistoni) is slightly heavier on average and the much lighter weight great grey owl (Strix nebulosa) is slightly longer on average.[6][12][13] Heimo Mikkola reported the largest specimens of eagle-owl as having the same upper body mass, 4.6kg (10lb), as the largest Blakiston’s fish owl and attained a length of around 3cm (1.2in) longer.[4][14] In terms of average weight and wing size, the Blakiston’s is the slightly larger species seemingly, even averaging a bit larger in these aspects than the biggest eagle-owl races from Russia.[6][13] Also, although 9cm (3.5in) shorter than the largest of the latter species, the Eurasian eagle-owl can weigh well more than twice as much as the largest great grey owl.[4][15] The Eurasian eagle-owl typically has a wingspan of 131–188cm (4ft 4in–6ft 2in),[4] with the largest specimens possibly attaining 200cm (6ft 7in).[16][17][18][19] The total length of the species can vary from 56 to 75cm (22 to 30in).[4][6][20] Females can weigh from 1.75 to 4.6kg (3.9 to 10.1lb) and males can weigh from 1.22 to 3.2kg (2.7 to 7.1lb).[4][21] In comparison, the barn owl (Tyto alba), the world's most widely distributed owl species, weighs about 500g (1.1lb) and the great horned owl (Bubo virginianus), which fills the eagle-owl's ecological niche in North America, weighs around 1.4kg (3.1lb).[22]
The fourth and most famous derivation of the evolutionary line that includes the Eurasian eagle-owl is the great horned owl, which appears to have been the result of primitive eagle-owls spreading into North America.[6] It has been stated that the great horned owls and Eurasian eagle-owls are barely distinct as species, with a similar level of divergence in their plumages as the Eurasian and North American representations of the great grey owl or the long-eared owl.[6] There are more outward physical differences between the great horned owl and the Eurasian eagle-owl than in those two examples, including a great size difference favoring the Eurasian species, the great horned owl’s horizontal rather than vertical underside barring, yellow rather than orange eyes and a much strong black bracket to the facial disc, not to mention a number of differences in their reproductive behaviour and distinctive voices.[14] Furthermore, genetic research has revealed that the snowy owl is more closely related to the great horned owl than are Eurasian eagle-owls.[14] The most closely related species beyond the Pharaoh, Indian and Cape eagle-owls to the Eurasian eagle-owl is the smaller, less powerful and African spotted eagle-owl (B. africanus), which was likely to have divided from the line before they radiated away from Africa. Somehow, genetic materials indicate the spotted eagle-owl appears to share a more recent ancestor with the Indian eagle-owl than with the Eurasian eagle-owl or even the sympatric Cape eagle-owl.[14] Eurasian eagle-owls in captivity have produced apparently healthy hybrids with both the Indian eagle-owl and the great horned owl.[4][6] The Pharaoh, Indian and Cape eagle-owls and the great horned owl are all broadly similar in size to each other, but all are considerably smaller than the Eurasian eagle-owl, which averages at least 15–30% larger in linear dimensions and 30–50% larger in body mass than these other related species, possibly as the eagle-owls adapted to warmer climates and smaller prey. Fossils from south France have indicated that during the Middle Pleistocene, Eurasian eagle-owls (this paleosubspecies given the name B. b. davidi) were larger than they are today, even larger were those found in Azerbaijan and in Caucasus (either B. b. bignadensis or B. bignadensis), which were deemed to date to the Late Pleistocene.[6] About a dozen subspecies are recognized today.[2]
Other than these two species, a large share of the raptorial prey for eagle-owls is made up of other owls. Given that all European owls are to some extent nocturnal, they may be encountered and killed upon detection by the Eurasian eagle-owl. In Europe, it has killed every other species of owl, from the tiny pygmy owl and scops owl to the large 1,078g (2.377lb) great grey owl and the 2,040g (4.50lb) snowy owl.[126] The Eurasian eagle-owl is the only raptor that has been known to prey on snowy owl on multiple occasions.[95][112][126] However, the threat Eurasian eagle-owls poses to other raptors can be exaggerated.[129] Occasionally, with adequate mammal prey populations, they can nest as close as a few dozen meters of other raptors and never harass them.[112] When nesting in the same groves as the 1,175g (2.590lb) long-legged buzzards (Buteo rufinus) in southeastern Bulgaria, Eurasian eagle-owls did not predate the buzzards at any point.[95][130] Long-legged buzzards have been killed however in Kazakhstan.[77] Even in those occasional cases where they pick off one or several raptors, they do not effect the overall population, unless the raptorial prey is already heavily diminished due to some other (often human-based) cause. For example, despite both being a known predator of both, they did not significantly depress numbers of either northern goshawks or tawny owls in southern Finland.[129] One study showed that many raptors engage in spatial avoidance during potential encounters with Eurasian eagle-owls and while the predation by eagle-owls did decrease raptor population densities, they seldom caused declines in breeding success or altered habitat occupancy.[131]
Larger and more dangerous mammalian prey is not infrequently tackled by Eurasian eagle-owl. Nearly thirty species of mammalian carnivores have been reported in their diet.[2] Many of these are mustelids, which are the smallest type of carnivore but can defend themselves viciously, even the tiny 67g (2.4oz) least weasel (Mustela nivalis).[79] Nonetheless, unlike some smaller birds of prey, the Eurasian eagle-owl seems to have no problem subduing various weasels and even martens, some of the latter can nearly equal to their own weight, and will kill the young of much larger species such as European otter (Lutra lutra) and Eurasian badger (Meles meles).[80][81][82] However, the single most widely reported carnivore is the red fox (Vulpes vulpes), as they've been recorded in the diet from Denmark and Spain to the Russian Far East.[20][72][83] Many fox specimens taken by eagle-owls are young individuals or subadults. Some studies posited that the average fox taken as weighing about 2,500 to 3,000g (5.5 to 6.6lb), about equal to the eagle-owl's own weight, but another noted fox specimens killed that were estimated to weigh 8,000g (18lb), much larger than the eagle-owls.[20][57][58][66] At least four other species of foxes have been verified as prey in the Middle East and Asia.[2][51][84][85] Raccoon dogs (Nyctereutes procyonoides), averaging 6,500g (14.3lb), have been preyed on in Asia as well.[86] Other relatively large carnivores have been hunted as well, including invasive Egyptian mongoose (Herpestes ichneumon) in Spain and masked palm civets (Paguma larvata) in China, both being roughly cat-sized at averages of 2,300 and 4,300g (5.1 and 9.5lb), respectively.[2][25][87] Domestic carnivores including cats (Felis silvestris catus) of all sizes and small dogs (Canis lupus familiaris) or puppies may on occasion become prey for Eurasian eagle-owls. Cats killed have been estimated to weigh from 3,200 to 7,500g (7.1 to 16.5lb).[20][37][66][87] The dogs killed by Bavarian eagle-owls were estimated to average 4,000g (8.8lb).[66] Non-native carnivores such as American mink (Neovison vison) and raccoon (Procyon lotor) have also been preyed on by eagle-owls, which is presumed to incidentally benefit the prey taken in considerably numbers by these rarely checked invasive fur-bearers.[88][89]
Most dietary studies place the average weight of Eurasian eagle-owl prey in the zone of 100 to 500g (0.22 to 1.10lb), thus the species fits well within the rule of thumb that most prey weigh no more than 20% of the raptorial bird's own weight.[17][23][24] It should be noted that the average prey weight in comparison to the eagle-owl's body mass is reportedly average and unremarkable for both owls and raptors in general, the average prey per one study was 7.2% of the eagle-owls’ body mass.[19] The European raptorial birds most likely to attack prey of a relatively large size compared to themselves were the black kite (Milvus migrans), whose average prey was 35.7% of its own weight, and the Eurasian pygmy owl (Glaucidium passerinum), whose average prey was 31.7% of its own weight.[19] On the other hand, when rabbit numbers were at their peak, the average prey mass in Spain may range up to at least 55% of the eagle-owls’ own body mass in that population.[20][25] A raptorial prey comparison estimated that the mean prey weight for eagle-owls in Europe was 294.7g (10.40oz) as a mean among 5 main regions, the highest of any owl but similar or slightly lighter than the European average for northern goshawks (Accipiter gentilis) and considerably lower only than two widespread European eagles. Per that study the average prey weight of the great horned owl in 4 North American regions was much lower (averaging only 64g (2.3oz)).[19] In Mediterranean scrub, the average mammalian prey of the Eurasian eagle-owl was nearly five times heavier than those of great horned owls from similar habitats in Chile, California and Colorado, where in combination the horned owl's mammalian food averaged 230g (8.1oz).[20] However, a comparison between eagle- and horned owls based upon six comparable biomes in the Americas and Eurasia found the great horned owl's prey averaged 372g (13.1oz), improbably slightly higher than the eagle-owl at 327g (11.5oz).[17] If known Asian studies are mixed with European ones, the average prey weight for the Eurasian eagle-owl overall may also roughly be 372g (13.1oz).[2][17] Among sympatric owls in Europe, the mean prey weight of long-eared owls (Asio otus) was found to be 32g (1.1oz), the tawny owl (Strix aluco) took prey weighing a mean of 34.5g (1.22oz) (though locally can be as high as 130g (4.6oz)) and short-eared owls (Asio flammeus) mean prey weigh was 35g (1.2oz).[2] A study in Finland seeking to distinguish the differences in prey taken by females and smaller male eagle-owls found that the two sexes prey averaged 828g (1.825lb) and 575g (1.268lb), respectively. The species taken as food by the two sexes there were largely the same but the female simply often caught the larger prey individuals.[26]
Hunting mainly consist of the owl watching from a perch for prey activity and then swooping down swiftly once prey is spotted. The prey is often killed quickly by the eagle owl's powerful grip and talons though is sometimes bitten on the head to be killed as well.[3] Then the prey item is swallowed whole or torn into pieces with the bill. The same basic hunting and killing methods are used by all owls in the Bubo genus, except that the snowy owls (Bubo scandiacus) and fish owls regularly watch for prey from a ground position (on a bank in the case of fish owls).[2][4] Most hunting occurs in wood-cloaked openings, often those carved out by wetlands or watersheds. While they can and do hunt within woodlands, they are not well suited to hunting in areas with dense understories, thick foliage or tree thickets, as they seem to hunt firstly by vision and only secondarily by sounds, unlike some other owls. Eurasian eagle-owls are too heavy with relatively modest wing areas to hunt extensively on the wing although this species’ relatively short, broad wings allow it low-speed maneuverability in the moments are it takes off after they spot a prey item. Because of the limits of its flying abilities, the Eurasian eagle-owl requires ample, elevated perches from which to watch for prey activity and thus in most areas it will not hunt extensively in open, treeless areas, unlike smaller owls like the barn owl (Tyto alba). Tree branches are often the main hunting perches used but they will also use rock formations, rubble with large rocks, hills with tall grasses or even a building, tall pole or other elevated manmade perch.[2][5][6][7] Occasionally, they may capture other birds on the wing, including nocturnal migrants, taking advantage of their distraction and diminished visual acuity to intercept them in mid-flight.[5] They seem to hunt mostly by opportunity, taking whatever detectable prey item that is available, preferably those that are active.[2] Most prey, even up to the size of small rabbits, are swallowed whole.[8] While a small rodent can easily be swallowed in an instant, if the prey item is large, the swallowing process can appear grueling and grotesque and in some cases eagle-owl nestlings have choked to death while attempting to swallow overly large prey (i.e. moorhens).[3][8] Small prey is often swallowed immediately after capture, although occasionally it is carried in the bill to the nest for the young or to a roost for quick consumption. Larger prey is normally carried in the owl's feet and is more likely than smallish prey to be brought to the nest due to its nutritional value.[3] Exceptionally large prey (probably any over 3,000g (6.6lb)) is consumed on the ground where it is killed, possibly being torn apart into manageable pieces. This leaves the owl vulnerable to loss of their prey to scavengers or to confrontations with heavier predators.[3] The undigestable portions of prey are regurgitated in the form of pellets as in all owls. Pellets of the Eurasian eagle-owl average around 75mm ×32mm (3.0in ×1.3in), thus they are around the same size as those of most other large Bubo owls, even the notably smaller great horned owl (B. virginianus). In some cases, pellets of Bubo owls can range up to 150mm (5.9in) in length.[3][9] Eagle-owl pellets average slightly larger (about 10%) than those of great grey owls (Strix nebulosa).[10] As is the case with all owls, pellets are indisputably the best method to examine the main diversity of prey consumed by an owl. However, it is also important to examine the prey remains left around a roost or nest when available. Larger prey, which may be torn apart before the eating of portions or fleshy parts of the prey item, is frequently determined solely by remains rather pellets as are birds, in which the wings, feet and some feathers may be removed before consumption.[8][11] As in the great horned owl, after capturing larger prey, the Eurasian eagle-owl often beheads it. In part, this may be due to making prey easier to carry off and, in both large owl species, it is considered a signature indicator for predator identification.[12][13][14]
Despite the alternate common name of giant eagle-owl, the Verreaux's eagle-owl is not the largest owl or eagle-owl in the world. It is, however, a very large and powerful owl species. This species is both the largest owl found in Africa and the world's largest owl to occur in the tropics. Among all the world's owls, it is fourth heaviest living owl, after Blakiston's fish owl ("Bubo blakistoni"), the Eurasian eagle-owl ("Bubo bubo") and the tawny fish owl ("Bubo flavipes"), and is also the fourth longest living owl (measured from the bill to the tip of the tail), after the great gray ("Strix nebulosa"), Blakiston's fish and Eurasian eagle-owls. Based on body mass and wing chord length, Verreaux's eagle-owl is about the same size as "medium-sized" races of Eurasian eagle-owl, such as those from Central Asian steppe ("B. b. turcomanus") and the Himalayas ("B. b. hemachalana"), slightly smaller than most northern Eurasian races, considerably smaller than Siberian and Russian eagle-owls, and somewhat larger than the smallest Eurasian eagle-owl subspecies, such as those from the Iberian Peninsula ("B. b. hispanus") and the Middle East ("B. b. omissus" or "nikolskii").
The Eurasian eagle-owl (Bubo bubo) may well be the most powerful extant species of owl, able to attack and kill large prey far beyond the capacities of most other living owls. However, the species is even more marked for its ability to live on more diverse prey than possibly any other comparably sized raptorial bird, which, given its considerable size, is almost fully restricted to eagles. This species can adapt to surprisingly small prey where it is the only kind available and to large prey where it is abundant. Eurasian eagle-owls feed most commonly on small mammals weighing 100g (0.22lb) or more, although nearly 45% of the prey species recorded have an average adult body mass of less than 100g (3.5oz). Usually 55-80% of the food of eagle-owls is mammalian.[1][2]
Although other birds of prey are seldom caught, given that they are wary, fast and can defend themselves well, the white-tailed eagle can be characterized as an opportunistic predator of such birds. Indicating that they are regarded as a threat to raptors is that they are frequently mobbed by a wide range of raptor species when displaying active flights, to a similar regard that the perhaps more aggressively predatory golden eagle is. Given the difficulty of this prey type, white-tailed eagles are likely to attack other birds of prey when the victims are distracted, whether by migration on windy days, nesting duties or when trying to capture their own prey, are previously injured or they may even capture one while the raptor tries to mob the eagle. Certainly, nestlings and fledglings can certainly comprise a large fraction of the birds of prey caught as well as adult ones. Other accipitrids they are known to have preyed upon, in increasing order of size are the Eurasian sparrowhawk ("Accipiter nisus"), western marsh harrier ("Circus aeruginosus"), black kite ("Milvus migrans"), European honey-buzzard ("Pernis apivorus"), common buzzard ("Buteo buteo"), northern goshawk, red kite ("Milvus milvus"), lesser spotted eagle ("Clanga pomarina") and eastern imperial eagle, in addition to osprey. Non-accipitrid raptorial birds, these more likely restricted to fully independent birds due to their less conspicuous nests, known to fall prey to white-tailed eagles include Eurasian pygmy owl ("Glaucidium passerinum"), boreal owl ("Aegolius funereus"), Eurasian hobby ("Falco subbuteo"), long-eared owl (Asio otus), northern hawk owl ("Surnia ulula"), short-eared owl ("Asio flammeus"), peregrine falcon ("Falco peregrinus"), snowy owl ("Bubo scandiacus") and Eurasian eagle owl ("Bubo bubo"). Accipitrid prey size ranges by body mass ranges from for a sparrowhawk to in the imperial eagle and that of non-accipitrid raptors ranges from for the pygmy owl to for the eagle owl and apparently both imperial eagles and eagle owls that were caught were adults. As true apex predators, healthy adult white-tailed eagles have no known natural predators.
The Eurasian eagle-owl is a very formidable bird of prey but its diet broadly overlaps with other European owls. All species of owl in the Europe and northern Asia hunt rodents, as does the eagle-owl, and in many the very same microtine rodents such as voles and lemmings will be favored.[95][112][113] Even the 58.5g (2.06oz) Eurasian pygmy owl (Glaucidium passerinum), at a whooping one-fortieth of the weight of an eagle-owl, will take much the same rodent prey as eagle-owls in adjacent habitats.[2][95] The only European owls to favor non-rodent prey are the 92g (3.2oz) European scops owl (Otus scops) and 169g (6.0oz) little owl (Athene noctua), both of which most regularly consume invertebrates. However, little owls also take rodents and small mammals, especially in the winter months (while scops owl migrate to Africa for the winter).[3] The European owls with the most similar diets to eagle-owls are 475g (1.047lb) tawny (Strix aluco) and 785g (1.731lb) Ural owls (Strix uralensis), although both are considerably smaller and less powerful and more specialized to hunt in wooded environments. These two Strix species are highly territorial and sedentary like the eagle-owl and capable of taking a broad range of prey, including good numbers of birds and larger prey such as rabbits (for the tawny owl) and hares (for the Ural owl) of up to at least twice their own weight.[2] Studies have indicated that even while selected similar prey species as the eagle-owl, smaller owls including the long-eared, tawny and Ural owls select smaller individual prey items, being more likely to take small, juveniles rather than optimal, large adults as does the eagle-owl.[95][114][115] Similar rodent prey is also often taken by many diurnal birds of prey, especially buzzards, harriers and small falcons.[116] However, due its greater size and power than overlapping owls and smaller diurnal raptors, it generally takes more diverse and larger prey than most overlapping raptorial birds.[2]
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.[6] 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.[4][7] The Strix is also related to the Bubo and is considered a "sister complex", with the Pulsatrix possibly being intermediate between the two.[14] 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.[6] 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%.[14] 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.[6][7][14] 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.[4][14] 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.[30] The mitochondrial DNA of the Indian species also appears considerably distinct from the Eurasian species.[14] 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.[6] 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.[14][31]
Apparently, the point at which the chicks venture out of the nest is driven by the location of the nest. In elevated nest sites, chicks usually wander out of the nest at 5 to as late as 7 weeks of age, but have been recorded leaving the nest if the nest is on the ground as early as 22 to 25 days old.[14] The chicks can walk well at five weeks of age and by seven weeks are taking short flights. Hunting and flying skills are not tested prior to the young eagle-owls leaving the nest. Young Eurasian eagle-owls leave the nest by 5–6 weeks of age and typically can be flying weakly (a few metres) by about 7–8 weeks of age. Normally, they are cared for at least another month. By the end of the month, the young eagle-owls are quite assured fliers.[6] There are a few confirmed cases of adult eagle-owls in Spain feeding and caring for post-fledgling juvenile eagle-owls that were not their own.[81]
Owls, which may have dissimilar periods of activity, are not entirely exempt from golden eagle predation either. Several species have been recorded as prey, especially in Northern Europe, Slovakia (where owls make up 2.4% of prey remains) and some parts of the Western United States. Species hunted have ranged in size from tiny Eurasian pygmy owl ("Glaucidium passerinum") and little owl ("Athene noctua") to the formidable, large great horned, Eurasian eagle and great gray owls ("Strix nebulosa"). Barn owls ("Tyto alba") have been predated by golden eagles in both North America and Eurasia. On Santa Rosa and Santa Cruz Islands, barn owls made up 4.5% of the diet, the largest known occurrence of that species in the eagles' diet. However, the great horned owl is the owl species that occurs most regularly in the diet of North American golden eagles. In Europe, golden eagles are relatively minor predators of owls compared to Eurasian eagle-owls and northern goshawks. The primary owls hunted by European eagles are Ural owls ("Strix uralensis") and short-eared owls ("Asio flammeus"). Few eye-witness accounts are known of owl predation, but one violent mid-day confrontation between a golden eagle and an adult great horned owl was witnessed in Jefferson County, Colorado. Although this owl was about a third of the eagle's weight, it was able to land some damaging blows on the larger bird. In the end, despite its wounds, the eagle was victorious over the dead owl. A case of kleptoparasitism by a golden eagle on a great horned owl has been recorded. Although the Eurasian eagle-owl is preyed upon by golden eagles (4 confirmed cases of golden eagles killing eagle-owls in Europe), in one case a golden eagle (age unspecified) was found amongst the prey in an eagle-owl nest.
Generally speaking, there appears to be rather strictly adhered size hierarchy among birds of prey and the very largest raptorial prey attacked by Eurasian eagle-owl tend to roughly equal to their own size. Larger raptors, such as eagles and vultures, seem to be largely invulnerable to eagle-owls. However, in Scandinavia, there are two cases of eagle-owls preying on “fairly large” nestlings of white-tailed eagles (Haliaeetus albicilla).[126] Given the size, average adult weight of 4,780g (10.54lb), and formidable character of this eagle, it is possible that the young of other raptors larger than themselves may too be attacked. Eastern imperial eagles (Aquila heliaca), which are nearly as large as the white-tailed eagle at an average weight of 3,215g (7.088lb), have been killed by eagle-owls in Kazakhstan.[139] Remarkable, considering the greater threat that the eagle normally poses to the eagle-owl than vica versa, it appeared a golden eagle was amongst the prey remains found around a nest in the French Pyrenees.[140] Cases in Spain where large, formidable birds of prey, the Egyptian vulture (Neophron percnopterus) and Bonelli's eagle, that are roughly equal in size to the eagle-owls, both weighing just over 2,000g (4.4lb), have been predated, these seem to be taken from the nest or shortly after independence and rare occurrences.[60][141] However, in Turkey, the eagle-owl is apparently a regular and serious predator of Bonelli's eagles.[142] The Eurasian eagle-owl predates the largest members of the most species-rich diurnal raptor genera: the 900g (2.0lb) northern goshawks from the Accipiter genus, the 1,375g (3.031lb) upland buzzards from the Buteo genus and the 1,460g (3.22lb) gyrfalcons (F. rusticolus) of the Falco genus.[112] Additional large raptors, i.e. those that can average 1,000g (2.2lb) or more in body mass, taken as prey include 1,485g (3.274lb) osprey (Pandion haliaetus), the 1,080g (2.38lb) red kites (Milvus milvus), 1,700g (3.7lb) short-toed eagles (Circaetus gallicus), the 2,205g (4.861lb) greater spotted eagle (Clanga clanga), the 1,370g (3.02lb) lesser spotted eagle (Clanga pomarina), and the rough-legged buzzards (Buteo lagopus) and saker falcons (Falco cherrug), in both of which females average more than 1,000g (2.2lb).[2][60][139][143][144][145] The taking of rough-legged buzzards and snowy owls must be confined to full-grown victims, since they nest further north than Eurasian eagle-owls.[2] Eurasian eagle-owls also hunt the smallest raptors available, including those such as lesser kestrels (Falco naumanni) and Japanese sparrowhawks (Accipiter gularis) that weigh less than 150g (5.3oz).[83] Some of these are cases of eagle-owls killing nestlings or fledglings but they can easily overtake adult buzzards, goshawks and falcons of any size.[2]
Hedgehogs often comprise a fairly significant portion of the prey taken by Eurasian eagle-owls, both in numbers and biomass. At least eight species of hedgehog have been predated. The European hedgehog is often one of the most prominent prey species in eagle-owl diet studies from Europe, and was recorded as the most numerous prey species per researchers in parts of Denmark, Switzerland, Austria and south Germany. With an average weight of 500 to 1,000g (1.1 to 2.2lb), the European hedgehog can comprise a very large portion of the biomass.[18][27][57][72] A study of the Bavarian region of Germany, the European hedgehog (the main prey species) made up 41.7% of the prey by number and 52.1% of the biomass, the maximum representation of hedgehogs known in Europe.[73] Other members of the Erinaceus genus are also locally regularly taken, as is the 575g (1.268lb) Daurian hedgehog (Mesechinus dauuricus) in Mongolia.[51] Studies from Greece and the Czech Republic found that the northern white-breasted hedgehog (Erinaceus roumanicus) was the leading prey species.[74][75] Unidentified Erinaceus hedgehogs almost totally dominated the diet of eagle-owls in Stavropol, Russia, making up 70.9% of the food, only the European rabbit has been found as more significant at the genera level by number in a given dietary study.[76] Studies from both Syria and Kazakhstan showed that the 365g (12.9oz) long-eared hedgehog (Hemiechinus auritus) was the most significant prey, making up 25.3% and 33.6% of the prey remains, respectively.[48][77] After killing hedgehogs, the Eurasian eagle-owls peel the prickly skin off their backs before consumption, frequently resulting in up to dozens of hedgehog backs being found around nests.[3][48][58] Moles and shrews are readily hunted but are usually only a secondary portion of the diet. Eurasian eagle-owls have been recorded hunting the smallest mammal on earth (by weight) the 1.8g (0.063oz) Etruscan shrew (Suncus etruscus), as well as the largest mole on earth, the 440g (16oz) Russian desman (Desmana moschata).[18][20] From the smallest shrew to the heaviest hedgehog, the Eurasian eagle-owl has been verified to hunt the full size range of insectivores. They've also attacked bats of every size available, from the smallest European bat, the 5.7g (0.20oz) common pipistrelle (Pipistrellus pipistrellus), to the largest species there, the 59g (2.1oz) greater noctule bat (Nyctalus lasiopterus). In the Sikhote-Alin range of the Russian Far East, bats were found to comprise 5.9% of the remains and, of five local owl species, the Eurasian eagle-owl was the most regular predator of bats in the area.[78]