Eurasian eagle-owl
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. 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. 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. 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"). 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.
Dietary biology of the Eurasian eagle-owl
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. 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). 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. 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. They seem to hunt mostly by opportunity, taking whatever detectable prey item that is available, preferably those that are active. Most prey, even up to the size of small rabbits, are swallowed whole. 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). 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. Exceptionally large prey (probably any over ) 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. The undigestable portions of prey are regurgitated in the form of pellets as in all owls. Pellets of the Eurasian eagle-owl average around , 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 in length. Eagle-owl pellets average slightly larger (about 10%) than those of great grey owls ("Strix nebulosa"). 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. 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.
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. 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. The primary prey species varies by region but is comprised mainly by small mammals such as voles, rats, mice, rabbits and hares. 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; 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. 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.