The Ural owl is a highly territorial and residential species that, as a rule, tends to stay on the same home range throughout the year. While most boreal owls, such as great grey owl and boreal owl, are generally given to nomadism and irruptive movements, with nearly the entire population following the population cycle of their primary prey, the Ural owl rarely departs from its home range even when prey populations decrease. Apart from the great grey species, like the Ural, most species in the Strix genus of owls are both highly territorial and non-migratory. Territories are generally maintained with songs, most often uttered by the male of the resident pair. This is quite the norm for owls in almost every part of the world. Due probably to its natural scarcity, very few firsthand accounts are known of territorial fights between adults but they presumably occur as Ural owls can be quite aggressive owls (or are at least in the context of protecting their nests). However, according to a study in southern Poland, Ural owls are generally less aggressive in the non-breeding seasons than are tawny owls to other owls and may be slightly tolerant of smaller owl species on their home range while the tawny is less so. That the Ural is slightly less aggressively territorial than the tawny owl is also supported in a study from Slovenia when tawnys had more spirited calls to recorded calls and launched more aggressive attacks to the taxidermied specimens of Ural, boreal and owls of their own species than did the Ural owls to any of the same stated stimuli. As for movements, as opposed to the sedentary adults, immatures may wander distances of up to about 150 km (93 mi). An occasional individual may wander straggle even further and remain for some time in a wintering area. A small number of straggling young Ural owls may occur irregularly down in southeastern Europe outside of the typical range of the species. Some circumstantial evidence was reported of Ural owls moving downhill in mountains in Japan when snowfall was heavy. Siberian population shows somewhat southward movements in severe winters, as the number of prey animals plummets and the owls themselves face risk of freezing.


This is a fairly powerful species of owl. However, like owls of nearly all sizes, mostly it prefers to take small prey relative to itself, especially small mammals. In a great majority of dietary studies, somewhere between 50 and 95% of the food is mammalian. Prey consists mostly of various species of rodent, though shrews and, locally, moles can be a regular food source as well. In additional, any variety of small mammal, to the size of hares (albeit usually young ones), may too be fairly often taken, as well as variable numbers of birds, amphibians and  invertebrates, with reptiles and perhaps fish being very rare prey. Across the wide distribution, the Ural owl is known to take more than 200 prey species, of which more than 80 are mammals. In a compilation study of the diet in three European study areas and four different years found that the mean prey body mass taken per nest was estimated to vary from 17.1 to 125 g (0.60 to 4.41 oz) with an average estimated at 43.83 g (1.546 oz).
Most hunting efforts are undertaken from a perch. They usually prefer prey that comes into open spots of the forest rather than those that frequent the forest floor. In Slovakia, in addition to glades and meadows near tall forests, Ural owls have been somewhat acclimated to hunting in open areas that are human sourced, including areas of forest fragmentation and even agricultural areas and small towns and villages if they are adjacent to mature forest patches. Little direct study has gone into the hunting methods of this predator. It is quite possible that is to some extent a still-hunter, perching for some time on a prominent tree until prey becomes apparent into the vicinity. However, in Scandinavia, Ural owls were reported to hunt more like goshawks rather than the more still-hunting tawny owls, with a perch-hunting method wherein they fly in brief spurts from perch to perch, with the flights meant to be inconspicuous until prey is detected. Ural owls are not known to attack prey from active flight, instead nearly always dropping down on it directly from its perch.  In Japan, experimental studies of semi-captive Ural owls were undertaken to observe how the owls select which areas to hunt in and which prey to select. When experimentally exposed to patches where prey was present and patches where prey was not present, Ural owls would forage in both but would seem to learn which patches were more likely to have food and subsequently forage more extensively around them. When the same biologists observed the foraging patterns on field mice and also voles, they similarly learned and showed a preference for the patches that held larger species over smaller ones. On evidence, though prey selection is largely opportunistic, rodents at risk of starvation in the Japanese studies were more likely to risk foraging in relatively open spots of the ground, so therefore would be preferentially selected by the Ural owls. Based on the Japanese studies, Ural owls seem to be able to improve their resource utilization patterns as they accumulate experience within their environment. Different studies in Japan showed that the Ural owls are capable of hunting prey that is hiding in shallow snow or near the snow’s surface during winter but voles hiding in the subnivean zone, ephemeral tunnels made under deep snow by the voles, are largely inaccessible to these owls. Surplus food may be stored at the nest or at nearby depots. The first verified record of scavenging on carrion was recorded when a Ural owl fed on the carcass of a roe deer (Capreolus capreolus), although an earlier record exists of a Ural owl visiting a wolf's kill (though it was not clear that the owl fed in that case).


Voles, small-to-medium-sized rodents with characteristically short tails, are often considered the most significant portion of the diet in almost every part of the distribution. Generally, in several parts to the west of their range, the Ural owl is associated with two vole prey species in particular, field voles (Microtus agrestis) and bank voles (Myodes glareolus). These voles tend to be solitary and fairly widely dispersed but habituate to favorable habitats for the Ural owls, such as the opener margins of extensive forested areas, and can quite numerous when vole populations peak. Per study in Finland, Ural owls took field and bank voles that averaged larger than the average weight of those captured in the field by biologist, i.e. the weight of those caught by owls was estimated at 28.59 g (1.008 oz) for field voles vs 26.44 g (0.933 oz) for bank voles, while those caught by biologists averaged 22.78 g (0.804 oz) for fields vs 18.75 g (0.661 oz) for banks. 56% of the field voles those caught by Ural owls were reproductively active, while 44% of bank voles were active as such. Helminths did not appear to make field voles more vulnerable to predation but male field voles were far more often caught by Ural owls than females, 76% of those caught in a study in Finland being male of those caught around vole nests, with 52% of the ones caught in fields being male. However, pregnant female field voles were found to be more vulnerable than other age female voles. More socially inclined and concentrated voles such as common voles (Microtus arvalis) tend to occur in more extensive open areas so forest-dwelling owls such as the Ural tend hunt them relatively scarcely, but only relative to many other predators. The largest known dietary study to date occurred in Finland, with 5995 prey items examined across several study years. According to this data, a much larger vole was preferred in the diet where available, the European water vole (Arvicola amphibius). With an estimated mean weight of 177 g (6.2 oz), the water vole constituted an estimated 22.15% of the prey by number and 52.2% of the biomass, against 19.5% by number and 18% of the biomass being made up by field voles. The average estimated prey weight overall within the study was estimated at 71.7 g (2.53 oz). Another, albeit smaller,  central Finnish study showed field voles leading by number over water voles, 42.7% against 33.9%, among 1739 prey items respectively, but with the two species constituting 17.4% and 69.1% of the prey biomass. Southern Finnish studies showed sharp shifts in the import of vole prey due to their population cycles. In southern Finland, of 3351 prey items in a peak vole year, 58.43% by number and 42.8% by biomass of the prey was made of by field voles, followed by bank vole at 12.41% by number (but only 5.73% by biomass) and water voles at 22.24% by biomass (but only 10.1% by number). In the same study area during a poor vole year, amongst 860 prey items, voles trailed other prey such as birds and shrews by number, but water voles were taken more or less in the same numbers here as in the peak vole years. Another study estimated the mean weight of Finnish Ural owl prey as 78.1 g (2.75 oz). Similar dietary habits were found for Ural owls in Sweden, in 2309 prey items, water voles made up 33.1% of prey by number and 60% of the biomass, field voles composed 30.8% by number and 14.5% of the biomass and bank voles made up 11.8% of the prey by number and 3.3% of the biomass. Camera traps recording captured 187 prey items for Ural owls in 5 nests in Värmland County, Sweden found that voles were secondary in delivery rates to common shrew (Sorex araneus) and various birds with the small size of such prey requiring frequent deliveries although this was offset with fair numbers of young hares apparently available to these owls.
As the Ural owl ranges south, prey populations tend to become slightly less cyclical but also apparent access to large prey such as water vole appears to be reduced. In the relatively northerly Latvia, of 2615 prey items, voles constituted just over half the diet and the prey base was relatively diverse. For Latvian owls, the main prey species were bank vole (at 18.09% by number, 9.2% by biomass), field vole (17.13% by number, 13.85% by biomass) thence European mole (Talpa europaea) (9.83% by number, 12.3% biomass), the latter at a mature mass of about 90 g (3.2 oz)). In Belarus, Microtus species were quite regular prey in vole peak years, at 45% by number and 29.9% biomass, against crash years when they were merely 6.7% by number and 4% by biomass while the less cyclical bank voles were 29% by number and 20.4% in biomass in peak years and 38.1% by number, 23.8% by biomass in crash years. Furthermore in Belarus, shrews and moles went from 6.4% to 14.3% by number during the peak and crash years (biomass in crash years was 13.1% though only 2.2% of this was from shrews). In the Beskids of southwestern Poland, the mean prey mass of 1039 prey items was a quite low 27.5 g (0.97 oz) with the main prey species being the bank vole, making up an average of 27.7% of prey by number and 25% of the biomass (average estimated weight 24.3 g (0.86 oz)), common voles constituting on average 24.9% of the prey by number and 25.8% of biomass (average estimated weight 27.5 g (0.97 oz)), yellow-necked mouse (Apodemus flavicollis) on average 15.73% of prey number and 17.4% of biomass (average estimated weight 30 g (1.1 oz)) and European pine vole (Microtus subterraneus) at an average of 8.9% of the prey numbers and 5.8% biomass (average estimated weight 17.3 g (0.61 oz)). Outside of voles and field mice, other prey appears to be largely negligible in the Polish Beskids. In Slovakia, amongst 2134 prey items, the main prey species were the yellow-necked mouse (21.8%), common vole (18.3%), bank vole (14.3%), striped field mouse (Apodemus agrarius) (4.9%) and European pine vole (4.7%). In the reintroduced Ural owls of the Bavarian forest among a small sample of 117 prey items, similar small rodent types were appearing to be largely selected, such as Apodemus species (16.2%), field voles (15.3%), bank vole (13.6%) as well as unidentified voles. Diets of the Ural owls towards the southeast part of the Europe range have mainly been recorded in Slovenia. The broadest study found that of 1268 prey items, 45.9% of the diet was voles, particularly the bank vole (38.1% by number, 26.24% by biomass), with another 34.2% made up of by Apodemus species (as well as 28.2% of the biomass) and a large portion of dormice, especially the large edible dormouse (Glis glis), at 6% by number and 25.5% by biomass. More locally in a smaller block within Slovenia, up to 58.8% by number and 94.4% by biomass in the Ural owl’s diet is compromised by the edible dormouse, whose adult body mass can vary from 62 to 340 g (2.2 to 12.0 oz).
Further east and out of Europe, the general reliance on small rodents for Ural owls is fairly consistent. In one of the most westerly studies, from Mordovia, Russia, of 426 prey items the main prey species were common voles (41.8%), bank voles (31.4%), tundra voles (Microtus oeconomus) (5.9%) and Ural field mouse (Apodemus uralensis) (3.1%). At five study sites in the Ural mountains region, among 870 prey items, 75.2% were mammals. 29.54% of the diet in the Urals were bank vole, 16.55% were common vole, 5.52% were wood mouse (Apodemus sylvaticus) and 4.83% were unidentified Myodes voles. Further east, the general reliance on Myodes, also known collectively as red-backed voles,  outside of the far-ranging bank vole seems to increase somewhat. Much further east in the Pacific coastal Primorsky Krai, 1163 total prey items were examined. Here rodents of similar character, though largely of different species, were largely taken by Ural owls, such as the northern red-backed vole (Myodes rutilus) (39.2% by number), reed vole (Microtus fortis) (24.24%), Apodemus sp. (9.7%), Korean field mouse (Apodemus peninsulae) (3.52%). In the isles of Japan, the smallish local races of Ural owls seem to assume the dietary generalist Strix owl ecological niche to some extent, in a similar way the tawny owl does to the west, however the primary portions of its diet are still assumed by many of the same prey genera taken elsewhere. In the Yatsugatake Mountains, 1026 small mammals were identified at 17 Ural owl nest of which Apodemus species compromised 71%, followed by voles, at 24%, and Japanese shrew mole (Urotrichus talpoides), at 5%. In Koshimizu, Hokkaido, of 266 prey items from 111 total pellets, the diet led by grey red-backed vole (Myodes rufocanus) (25.2%), large Japanese field mouse (Apodemus speciosus) (17.7%), and small Japanese field mouse (Apodemus argenteus) (15.8%).
Shrews of nearly 20 species are taken more or less throughout the Ural owl’s range. Although not significant typically in the prey mass for the owls, the taking of shrews may allow the owls to stave off hunger. The smallest mammal and vertebrate prey known to be taken by Ural owls is the Eurasian least shrew (Sorex minutissimus), which has a median adult body mass of about 2.5 g (0.088 oz). Other small mammals taken normally in rather low volume by Ural owls are bats, flying squirrels and weasels. Larger mammals are taken as well by Ural owls, and can be considered occasional supplemental prey despite often being significant in the prey biomass. The species takes mammalian prey larger than the typical voles and mice far less so than in larger owls such as eagle-owls.  Among these are a few species of squirrel, most of which weigh more than 200 g (7.1 oz) as adults, in Europe exclusively the far-ranging red squirrel (Sciurus vulgaris), as well as rats, especially the 300 g (11 oz) brown rat (Rattus norvegicus) which made up nearly 20% of the diet in a Hokkaido study. Adult hedgehogs of a couple species are opportunistically taken at times in Europe and European hedgehogs (Erinaceus europaeus) taken in Finland were estimated to average about 652 g (1.437 lb). Introduced muskrats (Ondatra zibethicus), which weigh on average an estimated 1,000 g (2.2 lb) when caught, are also taken in Finnish studies. They have been known to prey upon the Japanese giant flying squirrel (Petaurista leucogenys), which weighs around a median of 1,150 g (2.54 lb). One large mammalian prey widely associated with Ural owls are hares, though they seldom occur in substantial numbers in the diet, they appear to be opportunistically taken in most parts of the range. As much as nearly 25% of their biomass may be hares and hares are the largest known prey to be taken by Ural owls. While hunting hares, Ural owls usually focus their hunts on relatively young specimens. In Europe, both European hares (Lepus europaeus) and, especially, mountain hares (Lepus timidus) may be hunted. The mean size of mountain hares taken in Finland have variously been estimated at 173 to 2,000 g (0.381 to 4.409 lb), with a common median being about 500 g (1.1 lb). Exceptionally, Ural owls may take even adult mountain hares, which average about 2,900 g (6.4 lb), but this may be unconfirmed. Japanese hares (Lepus brachyurus) may also be taken in Japan as well.


The second most important prey group behind mammals (albeit considerably behind) is birds. Birds are also the most diverse prey group in the Ural owl’s diet, with well over 100 avian prey species recorded. Birds usually compromise less than 10% of the dietary intake by number in studies from Europe.  Exceptionally high numbers, relatively speaking, were reported in Fennoscandia, especially when vole numbers go down. In bad vole years in Finland, of 860 prey items, 32.2% by number and 40.25% by biomass were birds. In particular, thrushes of the Turdus genus were the most reported prey genera in these years, averaging 19.4% by number and 23.6% of the biomass. In Värmland County, Sweden, birds amounted to 25.6% of the prey by number and 32.67% of the biomass. A wide diversity of birds were reported, thrushes being again the most often identified. For central and southern Europe, the reintroduced population of the Bavarian Forest of Germany may show the highest results for birds at merely 11.1%. However, in the diet study within in the city of Košice, Slovakia, urban-adapted Ural owls were found to be relying almost solely on pigeons and doves for foods, namely the Eurasian collared dove (Streptopelia decaocto) and the rock pigeon (Columba livia) which constituted 76.7% and 13.4% of the contents of 16 pellets, respectively. In Russia, birds were far more significant overall in the Urals over other known studies, amounting to 17.01% of the 870 total prey items across different years and 47.6% among 146 prey items more locally near towns and villages in Perm Krai. In Japan, birds are somewhat more prominent in the diet of Ural owls compared to European data, usually compromising over 10% of the foods. The most birds reported in the diet of Japanese Ural owls were from 36 pellets found in Sakaide, Kagawa, which mainly comprised small birds, in particular the Eurasian tree sparrow (Passer montanus) (at 78.6% by number) and the white-cheeked starling (Spodiopsar cineraceus) (3.6%).
The hunting of birds by the Ural owl seems almost entirely based on opportunity as there is little evidence that they track down birds of any particular type, just merely upon the chance of encounter or detection. Thrushes are probably taken in many parts of the range due to their relative commonality in the habitat types used by Ural owls while other passerines that are widely taken also often have similar habitat preferences such as Old World flycatchers, finches and tits. Most passerines, and indeed most identified birds overall, are in between the size of a chaffinch (Fringilla coelebs), at a mean weight of 23.9 g (0.84 oz) and a Eurasian jay (Garrulus glandarius), at a mean weight of 160 g (5.6 oz). Bird prey may occasionally range down to the size of the 5.2 g (0.18 oz) goldcrest (Regulus regulus), which is Europe’s smallest bird species. The mean estimated weight of birds taken in Finland was estimated at 83.4 g (2.94 oz), being slightly higher than the weight estimated of mammals taken there. A diversity of corvids may be taken, ranging in size from azure-winged magpies (Cyanopica cyanus), at 96 g (3.4 oz), to carrion crows (Corvus corone), at 570 g (1.26 lb), but usually turn up in low numbers in dietary studies and these owls are far less prolific corvid hunters than some diurnal predators such as Accipiters. Other than pigeons and doves, non-passerine bird prey are usually taken relatively infrequently, although some prey families such as gamebirds and woodpeckers are also quite widely taken. An unusual preference for relatively large bird prey was reported in study from the Urals where the most frequently identified avian prey species were the 429 g (15.1 oz) hazel grouse (Bonasa bonasia) and the 490 g (1.08 lb) hooded crow (Corvus cornix). On infrequent occasions, Ural owls may be able to overtake bird prey of up to approximately their own size or somewhat larger, i.e. up to or slightly over 1,000 g (2.2 lb) in average body mass, such as adult mallard (Anas platyrhynchos), common goldeneye (Bucephala clangula), black grouse (Tetrao tetrix), common pheasant (Phasianus colchicus), chicken (Gallus gallus domesticus), black-crowned night-heron (Nycticorax nycticorax) and some accipitrids as well as, so far as is known, only young specimens of the larger still western capercaillie (Tetrao urogallus). Outside of aforementioned families other infrequently taken bird prey has included cuckoos, nightjars, sandpipers, terns, rollers and hoopoes.
Due likely in no small part to the scarcity of herpetological prey diversity in the temperate and often frigid haunts of Ural owls, reptiles are very infrequent prey for this species. However, sometimes frogs may be taken when an Ural owl opportunes upon one in the warmer months of the year. Usually, in nearly any part of the range, frogs and other amphibians constitute less than 6% of the regional diets for the species. In the small Swedish study from Värmland County, an exceptional 12.2% of delivered prey was common frogs (Rana temporaria). In spite of historic records of fish scales being found seldom in some pellets, there is no known reportage of confirmed predation on fish by Ural owls in dietary studies. There is little evidence that in most of the range that Ural owls invest much time into pursuing or feeding on insects and other invertebrates, since the food reward is low for a fairly large owl to habitually hunt such prey, which may weigh only about 0.2 g (0.0071 oz). However, occasionally, concentrations of insects such as woodboring beetles may attract an owl. In the Bavarian Forest, more than 6% of the diet consisted of insects, mostly unidentified beetles. Despite most studies from Japan showing up to about 95% of the foods being mammals and secondarily birds, sometimes more extensive association with insect prey is reported. In the Kagawa Prefecture, an exceptional 24% of the diet consisted of insects and furthermore in Kyoto, Ural owls were observed to be routinely pursuing and eating Japanese rhinoceros beetles (Allomyrina dichotoma). In Primorsky Krai, Ural owls were further recorded as preying upon Daurian crayfish (Cambaroides dauricus).


Ural owls regularly live concurrently in different parts of their range with other owl species. Most sympatric species also share a preference for small mammals, largely voles, especially when they occur in relatively northerly temperate places such as the haunts of the Ural owls. Thus, the Ural owl is frequently considered to be a competitor with sympatric owl species. Most especially, the Ural owl has often being compared and studied in areas of sympatry with its close cousin, the tawny owl. The tawny owl may co-exist with Ural owls today in many parts of the latter’s European distribution, including southern Fennoscandia, eastern and central Europe and European Russia. The dietary habits of the two species are largely concurrent, as in Uppland, Sweden, where prey species and groups were almost identical in rank of importance to their diets (i.e. field vole, water vole, Apodemus species, birds and frogs). On Mount Krim in Slovenia, both tawny and Ural owls took the same primary prey species but the tawny owl was shown to be adaptable to alternate prey during the low part of the vole population cycle while the Ural was less adaptive to alternate prey. The diets were largely similar between tawny and Ural owls as well in the Bavarian Forest of Germany but the tawny species took proportionately fewer field voles and more insects, and was estimated to take prey weighing on average 43% less than that taken by Ural owls. In Finland, food niche breadth for Ural owls overlapped about 73% with the tawny owl but the mean prey size was more than twice as much for the Ural owl, 38.4 g (1.35 oz) for tawny vs 78.1 g (2.75 oz) for Ural, and the tawny owl was recorded to take non-mammalian prey significantly more so than Ural owls. In Belarus, tawny owl prey sizes were between 31 and 49% smaller on average (utilizing two different calculation methods) than those of Ural owl but the smaller species had a considerably greater food niche breadth, which averaged 12.96 for tawnys and 5.48 for Urals. Compared to the tawny owl, the Ural owl is considerably larger in size and talon size (which is about 30% greater in the Ural), with the talon shape further indicating their different ecological roles, being proportionately shorter and more curved in tawny owls in accordance with its more varied diet and heavier and straighter in the Ural owl for dispatching relatively larger mammals. It is known that when ranges overlap between tawny and Ural owls, the Ural owl tends to dominate and sometimes kill the tawny owl. In Slovenia, Ural owls actually responded more consistently to recorded calls of tawny owls (40% of call exposures causing a vocal or physical response) than to recordings of calls of their own species (34% of call exposures eliciting a response). However, cases of interspecific killing between the species are fairly infrequent, and recent study indicates that the tawny owl’s relatively checkered distribution in northerly areas such as Fennoscandia is not likely due to this competition but rather due to the regional habitat type favoring the Ural owl. The tawny owl is not as well suited to taiga habitats as is the Ural species and locally are less suited to alternate nest sites (i.e. nesting in areas lacking tree cavities or nest boxes, whereas the Ural can locally also use old bird nests and tree stumps). Warming average temperatures in Fennoscandia have appeared to effect many owl species negatively due to the limiting nature on vole cycles, but the tawny owl, being confined to the south, has had the most decreased effect locally due to the lowering vole numbers (and despite their general ability to adapt to different prey) while the Ural owl, in central Finland at least, is not yet showing as drastic a negative effect due to this. Similarly, the tawny owl and Ural owl are largely segregated by altitudinal range and habitat in eastern Europe (i.e. the Carpathian mountains) and Poland, with little evidence that this is due to interspecific competition or predation but rather the suitably of the montane habitats. Here the tawny owl tends to occur at lower elevations while the Ural owl occupies the foothill forests at higher elevations. Generally, despite higher densities of the Ural in some mountainous parts of central and eastern Europe, the tawny owl is far more numerous in all countries of that region than the Ural owl. In Slovakia, 13.3% of Ural owl territories overlapped with those of tawny owls, a relatively low overlap given the overall environment. Despite the Ural owl’s presumed dominance, in Slovenia, a tawny owl was observed to fiercely attack a Ural owl until it left the vicinity, though it is not clear whether this was a territorial encounter or antipredator mobbing. In Poland, during post-dispersal in winter tawny owls were able to temporarily utilize parts of Ural owl territories, taking advantage of the Ural owls less aggressive behaviour outside of the breeding season.
Ural owls do not generally occur with other Strix owls excepting the tawny owl but overlap in much of their range also with the great grey owl, which furthermore ranges farther north and into the Americas as well. Despite its large size, the great grey owl is a dietary specialist on voles, relying almost exclusively on them. Its dietary restrictions are indicated by its foot morphology, with the great grey owl possessing talons that are conspicuously finer, smaller and less powerful looking than those of the Ural owl despite the slightly larger overall foot size (in correspondence with its body mass) of the great grey. Within the taiga that both the great grey and Ural owls prefer, great grey owls have been shown to nest in a wide diversity of locations, with more nest types overall than the Ural, but it does not normally use tree cavities as do the other two European Strix owls and seldom occurs in areas where conifers are not dominant anywhere in its range, such as riparian zones where forest can diversify to become mixed with deciduous trees. The difference in nest site usage and narrower dietary habits of the great grey are thought to mitigate most serious competition between the great grey and Ural owls. A larger owl than either species, however, is the Eurasian eagle-owl. The Ural owl is considerably smaller-bodied (around three times lighter), with a wingspan around 35% smaller and smaller talons and feet, so a competitive advantage is apparent even between the species’ morphology. The eagle-owl also takes a large number of small prey such as voles but is conspicuously more variable in alternate foods. Across a similar but generally much broader distribution (both in latitude and longitude), eagle-owls take about three times as many prey species as do Ural owls, including much more species from all prey taxon, and also occur in a broader range of habitat types. Being much larger and (based on morphology) presumably much more powerful, the eagle-owl is able to take much larger prey than the Ural owl. More locally, in Finland, the Ural owl took proportionately more European water voles, overall birds and amphibians than did the eagle-owls but took far fewer gamebirds. The eagle-owls are likely avoided when possible by the Ural. Upon evidence, Ural owls are fairly regular in occurrence in North Ostrobothnia, where eagle-owls are rare to absent, but in South Ostrobothnia the Urals are scarce, possibly because the eagle-owls are relatively common. However, habitat differences may segregate the two species as well. In Finland, the eagle-owl appears to prefer pine-dominated forest while the Ural prefers spruce-dominated forests. Elsewhere, eagle-owls may frequent rocky areas where available (for nesting) and often hunt in more diverse and often more open areas, and in such areas Ural owls are rare to absent. Being smaller than the great grey owl and Eurasian eagle-owl, it is projected that the Ural owl can live off of less food overall than them. It is estimated that over a 6 month period, an Ural owl needs about 22.8 kg (50 lb) of food while a great grey owl needs about 27.4 kg (60 lb) and an eagle-owl needs about 54.8 kg (121 lb). The Ural owl has the potential to encounter other larger owls such as the snowy owl (Bubo scandiacus) in winter and the Blakiston's fish owl (Bubo blakistoni) in the far east of the range, but are unlikely to interact extensively given the differences in habitat usage.
Apart from the aforementioned species, most other owl species that the Ural owl encounters in its range are significantly smaller. Furthermore, the Ural owl tends to dominate these species when encounters occur and so may be avoided. One species that often shares similar habitat and prey preferences with the Ural owl is the boreal owl. However, based on territory spacing, the boreal owls can appear to more strictly avoid the tawny owl, which is known to be highly aggressive in its territorial behaviour year-around while studies have indicated territorial exclusion by Ural owls is largely confined to the breeding season. It was hypothesized, however, in forested southern Poland that boreal owls selected nest sites not out of avoidance of tawny owls but based on the availability of suitable nesting sites. In the south Poland study, tawny owls usually occurred more so in fir-spruce woodland. In Slovenia, it was theorized that boreal owls incidentally benefited from the exclusion of tawny owls by dominant Ural owls when the three species occurred in adjacent habitats. However, evidence indicates that the boreal owls faces higher mortality when they nest too close to Ural owls, i.e. within about 2 km (1.2 mi). A similar relationship has been detected between the Ural owl and the Eurasian pygmy owl (Glaucidium passerinum), a species less than half the size of a boreal owl. However, the pygmy owl usually selected different forest types than Ural owls in areas of sympatry, in particular fir woodland, wherein the Ural tends to be rare or absent. However, ecological interactions were detected in Slovenia, as the pygmy owl was observed to display antipredator behaviour against Ural owls. Despite the different preferred forest habitat, 46.3% of ranges of Ural and Eurasian pygmy owls overlapped in Slovakia. Quite little is known about the ecological interactions between the Ural owl and the northern hawk owl (Surnia ulula), another boreal owl, despite a shared propensity for utilizing snags as nest sites. Hawk owls are also routine vole predators but share more ecological characteristics with the great grey owl than the Ural owls, in particular their nomadic behaviours and irruptive movements. Furthermore, hawk-owl’s stronger tendency for diurnality may further provide a degree of partitioning.
The best known aspect of interspecific interactions with other owls and assorted other predators is interspecific predations. The Ural owl is at times vulnerable to predation by larger predators when encounters occur. Undoubtedly, the most dangerous predator is likely the Eurasian eagle-owl. Other predators known to prey upon Ural owls have included golden eagles (Aquila chrysaetos), eastern imperial eagle (Aquila heliaca), mountain hawk-eagle (Nisaetus nipalensis) and Eurasian lynx (Lynx lynx) as well as diurnal raptors that are only slightly larger, including the northern goshawk and lesser spotted eagle (Clanga pomarina). In most cases mentioned above, the age of the Ural owl taken by the predators are not usually specified (although any of the first three large eagles are certainly capable of striking down Ural owls potentially of any age). In some cases, goshawks have been known to kill parent Ural owls apparently entirely out of competition (despite different main food sources) and lay their eggs on a nest still containing the owls’ eggs. Predators specifically noted to have taken young Ural owls, usually of around fledgling age or shortly post-dispersal (especially those used in reintroductions) have additionally included red foxes (Vulpes vulpes), European pine martens (Martes martes) and great grey owls. In Primorsky Krai, Asian badgers (Meles leucurus) and raccoon dogs (Nyctereutes procyonoides) are mentioned as potential or likely predators of Ural owls nests as well. In one recorded instance, a Ural owl that was observed seemingly trying to prey upon a non-native American mink (Neogale vison) was seen to lose the confrontation when the mink turned the tables, having apparently overpowered, killed and ate the owl. Although predation events upon Ural owls are widely reported, the relative number of incidents of such are very low and singular. South of the Arctic, it can be considered to rival the great grey owl as the owl species that is second least vulnerable to predation, behind the apex predator eagle-owls. The Ural owl is itself a fairly formidable predator of smaller owl species, although not as prolific a killer as are eagle-owls and northern goshawks. Among the owls Ural owls have been known to have preyed upon are Indian scops owl (Otus lettia), collared scops owl (Otus bakkamoena), northern hawk-owls, tawny owls, Eurasian pygmy owls, boreal owls and long-eared owls. Diurnal raptors are also sometimes vulnerable to predation by Ural owls, including grey-faced buzzards (Butastur indicus), Eurasian sparrowhawk (Accipiter nisus), common kestrel (Falco tinniculus) and even apparent adult northern goshawks. Thus the Ural owl, coupled with a very low known rate of natural predations, appears to occupy a similar position in the intraguild predatory hierarchy as the goshawk. In Finland, both smaller owls and diurnal raptors such as sparrowhawks and even buzzards appear to avoid nesting near Ural owls. In addition, Ural owls are known to have successfully have chased off actively nesting goshawks as well as European honey buzzards (Pernis apivorus), common buzzards (Buteo buteo) and black kites (Milvus migrans) in order to claim the nests for themselves. Despite their potential predation on smaller mesopredators, when nest boxes for European pied flycatchers (Ficedula hypoleuca) were experimentally placed in the area of Ural owl nests, productivity lowered, and it is possibly because mesopredators were often attracted to the corresponding food base of the owls. On the contrary, experimental ground nests put out by researchers with random poultry eggs in central Finland were shown to be incidentally protected by the fierce presence of Ural Owls. In the Finnish ground placed almost directly under the Ural nest none at all were preyed upon, while in those placed 100 m (330 ft) away, 8.3% were predated, and those within 200–400 m (660–1,310 ft) experienced an average predation rate of 58.3%. At a great distance, at 500–900 m (1,600–3,000 ft) all ground nests were predated.


The Ural owl generally pairs for life and maintains a territory for several years. Mate retention in Fennoscandia was found to have averaged 98–100% in males and 90-95% in females, making it amongst the most monogamous birds of prey of any order (or at least well-studied bird of prey species). Territories of Ural owls are on average about 3 times larger than those of tawny owls. In Sweden, about 3000 pairs of Urals are found in an 150,000 km² (58,000 sq mi) area. In Finland, nests are usually somewhere between 2 and 4 km (1.2 and 2.5 mi) apart in wildland areas. Per Finnish data, the Ural owl had the second most nest found for an owl species from 1985-1989, with 901 nests second to the boreal owl with 2265 nests. In Croatia, different areas had anywhere from 1.1 to 5.4 pairs on average per 10 km² (3.9 sq mi) with an estimated 700-1000 breeding pairs left in the estimated 37% of Croatia that is still forested. The peak Croatian population was recorded in Plitvice Lakes National Park, predominately in mixed fir-beech montane forest, which held about 38 breeding pairs. Breeding in Slovenia is at a mean elevation of 850 m (2,790 ft), with altitude less important than habitat. Many forest types were used in Slovenia but fir-beech mixed forest were seen to be most often utilized. The highest Slovenian densities were around 2-3 pairs per 10 km² (3.9 sq mi) for Mount Krim and around 4-5 pairs per 10 km² (3.9 sq mi) for Snežnik. In 2016, it was estimated  that Slovenia holds 400-700 pairs. Survey of the species in Silesian Beskids was done, where the population may represent a recent population expansion. With as many as three breeding attempts, Density was estimated at 0.6-0.9 pairs per 10 km² (3.9 sq mi), 3-10 times lower than other nearby ranges in eastern Europe like the Low Beskids and Bieszczady Mountains. A low density population was found for Pieniny National Park, Poland with 0.9-1.3 per 10 km² (3.9 sq mi). The average density in the Polish Kraków-Częstochowa Upland was 1 pair per 10 km² (3.9 sq mi). In the northern part of Moravia, Czech Republic, 3-5 pairs were recorded around the turn of the 21st century, an almost certain population increase. A population increase noted in the Roztocze area of the Ukraine, despite the forest being mixed rather than the subspecies' preferred beech dominant, now up to 1.7 pairs per 10 km² (3.9 sq mi). Where nest boxes were put up for Ural owls in Samara Oblast showed the owls taking up residence in boxes at an average distance of 1.5 km (0.93 mi); against which the average distance of all installed boxes was 1.11 km (0.69 mi).


The clutch size is typically 3-4 (rarely from as few as 1 to as many as 6), with the eggs being pure white and quite rounded. The mean egg laying dates in Fennoscandia are between mid-March and late April. In montane Slovenia, somewhat surprisingly, it is slightly later at late March into early June. Mean clutch size was found to be 2.93 in Sweden. Mean clutch size in Finland was 2.24 but could range from 2.08 to 3.98 on average in poor and good years for vole prey. Mean clutch size in Slovenia is about 3.3. Another Slovenian study showed a fairly lower mean clutch size of 2.4 with evidence that clutch was reduced by low food access in the early part of the breeding season. Clutch size in a small sample from Nizhny Novgorod Russia was found to average 3.6. The clutch size average in nest boxes of Samara Oblast was 2.4. Egg sizes are usually between 46.5 and 52.3 mm (1.83 and 2.06 in) in height by 39 to 44 mm (1.5 to 1.7 in) in diameter, and the eggs weighing on average about 47 g (1.7 oz) when fresh. Based on studies in southern Finland, amongst 59 studied females, egg size varies by 22.4% through the cycle years and the largest eggs are roughly twice the mass of the smallest, a very considerable variation. The eggs are laid directly to bottom of nesting surface in roughly 2 day intervals. Females alone incubate usually beginning with the first egg, and is fed by her mate throughout. In 108 female Ural owls from Finland the start of incubation varied individually, with synchronous hatching shown to be disadvantageous to overall productivity. Evidence was found that females repeated their incubation start time annually was moderately strong (26% repeatability) so it may be an evolved trait. Incubation lasts for 28 to 35 days and averages about 6 days longer than the incubation period of the tawny owl. The hatchlings break at concurrent time lapses as the eggs are laid (about 2 days), the females staying by until fledging. The downy chick is white; at the stage when they typically leave the nest (or mesoptile stage) the downy is pale dirty whitish and barred with greyish-brown on head, nape, mantle and underparts. Nestlings leave the nest at about 35 days old and can fly at 45 days. They are fed and cared for over an additional 2 months or so after leaving the nests.


The young Ural owls officially reach sexual maturity in the year after independence. However, in southern Finland, it was found that first time nesting females generally would not attempt to nest if it was a poor vole year and the largest percentage (about 40%) first started breeding attempts in intermediate years (between poor and good vole years), which often did not occur until they were 3 to 4 years old. The same typical age (3–4 years) was detected in central Sweden, despite the females often being on territory within their first year. Upon study of feather molt and wear, it was supported that some female Ural owls breed in their 2nd or 3rd year, but most do not breed until their 4th or 5th year. On the contrary, a Finnish study found that for Ural owls of both sexes, it was estimated that the mean starting age for breeding is 2.9 years, with an average breeding life expectancy of 3.3 years. Furthermore, females that started breeding at 2 or 3 were shown in Finland to have higher reproductive “fitness” than females who started breeding at 4 or older. Females laid eggs in Finland an average of 2.7 times in their life and produced an average of 6.7 fledglings over their reproductive lifetime (with the most productive females producing up to 33 fledglings). Brooding activity peaks, with typically 9-14 daily visits, in Finnish studies in the late evening during spring and summer while tending to young, with a weaker peak activity time in the early morning, both timed to peak prey activity times. It is well known that mother Ural owls defends her brood in a fearsome display. In Finland, the repeatability of the nesting defense behaviour by females was ranked as 52.4%, starting with a bark and taking flight, then fly-bys towards the perceived threat and culminating in attacks and powerful strikes. Per this study, those females that laid their eggs earlier on average defended their nest more vigorously than those who laid their clutches later. The force and ferocity of the attack led to its common name in Swedish (Slaguggla or “attacking owl”), and their attacks can potentially cause grievous physical harm even to an animal as large as a human. In at least some cases, humans experience the loss of one eye or have been blinded, with broken eye sockets or eyeballs extracted by Ural owl attacks. Due to her attacks, the predation rate on Ural owl is often exceptionally low. Partial feather molting by females was thought to not have great bearing on her brooding abilities, since it was largely timed to periods where the female (and her brood of offspring) are being almost entirely fed by the male of the pair.


Broods with more than three chicks sometimes experience siblicide per study in southern Finland, but instances of siblicide are rare otherwise. Larger clutches seem to be an insurance behaviour since authors showed that broods of 4 or so were more likely to have younger sibling die sooner or later before independence. Productivity is largely associated with prey access, with the effect most studied in Fennoscandia because of the dramatic 3 year fluctuation of vole prey appears to cause great variations in productivity. Natality rates could vary from zero to 2.9 across the years based on prey numbers in Sweden, with the average being 1.03-1.12 fledglings per pair and 2.68 fledglings per successful pair. However, it was estimated in Sweden that on average 62% of owls do not survive their first year, in comparison to adult female annual mortality which was estimated at 10.5%. Similarly, in southern Finland, from 29 to 58 breeding pairs bred annually in the same study area and could produce anywhere from 1.17 to 3.21 fledglings depending on prey cycles (3.5 average fledglings per successful attempts in high vole years against 1.79 per successful nest in low vole year). Finnish study showed that 21.7% of all clutches failed to hatch and 4.3% died completely after hatching. Hatchability in south Finland averages 87% across all years. On a broader scale, from 422-1710 territories were recorded in Finland from 2009-2011 with the number of successful nests ranging annually from 168 to 1341. The population trends were more or less mirrored by those of the Finnish tawny owls but tawny brood size averages 0.68 larger than that of the Ural. Prospects for breeding are generally low during the low point of the three year cycle of the vole prey of Urals in south Finland but paradoxically when a high vole year is followed by a low one, the number of attempted clutches is higher but the rate of nest failure is higher. For instance, within a Finnish study, 144 eggs were found in 63 nests during a low vole phase, in the increase phase 1212 from 338 nests and in peak phase 1259 eggs from 345 nests. However, this study showed low recruitment from clutches was detected in both increase and peak years, and the complications and individual variations of each pair may cause variations that the previous theories do not account for. Breeding success in southern Finland was also driven by the mother Ural owl’s age, with 3-5 year old females being less productive than those that were 6 to 9 years old, and that older females, of more than 10 years old, tended to lay larger and more rounded eggs. In Finland, supplemental fed pairs nest up to 1 week earlier and produce up to 0.6 more eggs than those that were not, therefore food limitation does appear to effect productivity of the species. Males were mildly more numerous in Finland among fledged young (56%) but survivorship of the two genders were essentially equal and body mass in both sexes averaged about 6% more in good vole years. Studies of 274 Finnish adult females found that 18% of them produced about half of the fledglings. Breeding attempts in Nizhny Novgorod Russia produced an average number 3.1 young to leave the nest.
Despite being farther south than many aforementioned studies (i.e. from Fennoscandia), in Estonia a highly variable breeding success rate was observed to be concurrently happening during prey population cycles. In Slovenia, about 80% of breeding attempts manage to produce at least one fledgling. Another Slovenian study showed a nearly 5% higher breeding success overall due to late summer peaks of edible dormouse (July or later). 7 nests in Podkarpackie Voivodeship, Poland were shown to able to produce an average 2.8 fledglings in a good year but no nest could be found in a poor rodent year. Findings showed that parent Ural owls, particularly the adult female, are able to adjust their breeding cycle to maximize survivorship of their young well given the experience accrued during their relatively long lifespan, and are relatively successful at mitigating issues such as parasitism and infestations in nest boxes if they are being used. Post-dispersal young from Vienna Woods in Austria were radio-tracked and showed a mean dispersal distance of 8,778 m (28,799 ft) from release site and were shown to experience about a 23% mortality rate.


The Ural owl is not a densely populated bird but can be locally not uncommon. The IUCN estimates that there are between 350,000 and 1,200,000 individuals living in the wild globally. Most decreases in recent history have been reported from areas where hollow and broken trees were removed from forests. In Estonia, managed forest almost invariably have fewer Ural owls than undisturbed forest has because of reduction of snags and other natural cavities to use. However, the general trends are positive for most European Ural owl populations. The erection of nest boxes has caused population increases in several parts of the range, especially Finland. In eastern Europe, it is one of the more stable owl species, though it is far less numerous overall than some (i.e. tawny, long-eared, and little owls (Athene noctua)). Several population increase and expansions have been detected in central and eastern Europe for Ural owls in recent history, in sync with other owls considered boreal species (i.e. great grey, boreal, Eurasian pygmy). Previous records indicated staple populations in the 1980s for Ural owls in the western Carpathian mountains (estimated at about 1000 pairs) and northern Belarus (at 50-100 pairs). By the 1990s, the number had grown to 1000-1500 pairs in the western Carpathians and to 220-1350 pairs in northern Belarus. By 2005, the numbers were up to 3500 pairs in Carpathians and a drastic increase to 2700-4300 pairs in Belarus. In the Czech Republic, partially due to deliberate reintroductions, the numbers went from 1-5 pairs in 1985-89 to 25-40 pairs by 2001-2003. In selected plots of southeastern Poland, Belarus and Latvia, densities went from 1-2 pairs per 100 km² (39 sq mi) to 10 pairs per 100 km² (39 sq mi). In these three countries, northern population now much higher density than southern ones, i.e. 5-8.1 pairs per 100 km² (39 sq mi) in north to 3.1-3.6 pairs per 100 km² (39 sq mi) in the south. A range expansion of Ural owls was detected in western Ukraine (in the general region of Roztochya Biosphere Reserve and Yavorivskyi National Park). in 2005-07 up to 1.7-2 pair per 10 km² (3.9 sq mi) whereas in the past (i.e. to the 1990s) the species was a rare vagrant to this area. This density of this Ukrainian population is higher than seemingly most in Scandinavia and Belarus but lower than in southwestern Poland and Slovenia; while whether this represents a population increase or merely a population shift is unknown nor its relation to forestry. In some parts of Slovakia, such as Slanské vrchy, Vihorlat and the Ondavská Highlands the density of pairs may be up to a pair per square kilometer, perhaps the highest known specieswide. 400-500 Slovenian pairs from 1973-1994 is as of 2006 is estimated at 1400-2500 pairs. In the Orava region of Slovakia, the population may have increased fivefold during the above stated years. While many owl species (eagle-owl, long-eared, boreal) have appeared to have generally declined in period of 1982-2007 in Finland, to the contrary Ural owls increased by about 1% (excluded from these estimates were too difficult to analyze northerly nomadic owl species). In every regard but number of nestlings that were ringed (in which it also trails the Eurasian pygmy), it has been observed the Ural is the 2nd commonest detected breeding owl after the boreal owl in Finland with  2545 territories found, 1786 nests observed and 4722 nestlings ringed. An increase of the population was found in the Moscow region where tall stands remained despite the rather developed environment nearby.
Occasionally, Ural owls are vulnerable to flying into manmade objects. In most parts of the range, they are less vulnerable than many other large birds of prey (in part because of their preference for remote forests) but certainly a few are likely to be claimed as such. Many such mortalities are due to wire collisions and electrocutions, which are likely increase especially as populations expand and move into areas closer to human habitations. Other collision kills, such as with glass buildings and, widely, with various automobiles, may too potentially be on the increase. Though historically subject to some degree of persecution, Ural owls were spared from the worst of it perhaps by nesting in remote forests and possibly by being generally less predatory to small domestic fowl, game animals and the like than large raptorial birds like Eurasian eagle-owls, golden eagles and northern goshawks, all of which were badly persecuted and thusly reduced. Like other wild birds, Ural owls may be vulnerable to some degree of mortality due to diseases and infections but these are unlikely to compromise overall populations. A case of the bacterial infectious disease Tularemia was observed in an ural owl as was Usutu virus in a single bird. 71.4% of 14 wild Ural owls in Japan had blood parasites while a smaller but still present number of Acanthocephala and roundworms were detected in known European data. Many Japanese Ural owls were also found to be vulnerable to biting lice.


Species reintroductions have been undertaken in some different parts of Europe. By far the best documented Ural owl reintroduction was in the Bohemian forest, which ranges between the countries and regions of Bavaria in Germany, the Czech Republic and upper Austria. Previously the species was extinct here by 1926 (by 1910 on the Austrian side). Established of captive breeding stock occurred between 1972 and 2005 (with origins from 7 different countries and a mixture of the two main European subspecies). For this breeding program, 212 young Ural owls were originally released. During the study, experimental introductions were made to tawny owl nests, although this potentially exposed them to risk of hybridization. Otherwise, parentage consisted of relatively newly established Ural owls. Both tawny and Ural owls were shown to be able to successfully raise the young Ural broods. Food was also offered to pairs at nearby release pens and 60 nest boxes erected to compensate for lack of nest sites, especially in areas of secondary forest. 33 Ural owls were recovered dead, while an additional 4 were weakened or injured to the state of being unable to continue to live in the wild. Most of the mortality was due to electrocution or were hit by cars but a few were illegally shot. The first wild breeding of an Ural pair in the Bohemian forest occurred in 1985 but the first successful breeding was not until 1989 (with the pair having producing 4 offspring). Between 1981 and 2005 a total of 49 broods were recorded, 31 of which were successful with 59 young produced (avg 1.3 per all attempts, 1.9 per successful pair). No fewer than 6 pairs (possibly 5-10 breeding pairs) were established by the end of study, with the carrying capacity within the forest estimated at 10 pairs. For a self-sustaining breeding population, it was felt that at least 30 pairs are necessary in the general area within connected corridors to the Bohemian forest. Therefore, 87 birds were introduced into nearby Sumava National Park between 1995 and 2006, an estimated 2-3 breeding pairs have established there now. A still uncertain pilot program in Mühlviertel, Austria may or may not have produced a pair as well. In 2001, among two reintroduction attempts in Austria, both failed. All told from the entire Bavarian reintroduction, it was said that the owls producing a total of 204 offspring between 1972 and 2014, although many of these may not have survived. More successful than the Austrian part of the Bavarian forest reintroductions was the reintroduction elsewhere in Austria, namely the Vienna Woods. In this project, 67 young owls were released between 2009 and 2013.  A nesting box network of 127 boxes were set out to be utilized and one of Europe's largest stands of beech trees was present. In the Vienna Woods, the survival rate was high at about 70.5%. By 2011-2012, 10 pairs attempted to nest, establishing home ranges averaging about 300 ha (740 acres) and produced 3.1 fledglings per successful pair.


The barred owl (Strix varia), also known as the northern barred owl, striped owl or, more informally, hoot owl, is a North American large species of owl. A member of the true owl family, Strigidae, they belong to the genus Strix, which is also the origin of the family's name under Linnaean taxonomy.  Barred owls are largely native to eastern North America, but have expanded their range to the west coast of North America where they are considered invasive. Mature forests are their preferred habitat, but they can also acclimate to various gradients of open woodlands. Their diet consists mainly of small mammals, but this species is an opportunistic predator and is known to prey upon other small vertebrates such as birds, reptiles, and amphibians, as well as a variety of invertebrates.
Barred owls are brown to gray overall, with dark striping on the underside. Barred owls have typical nesting habits for a true owl, tending to raise a relatively small brood often in a tree hollow or snag (but sometimes also in other nesting sites) in forested areas. As a result of the barred owl's westward expansion, the species has begun to encroach on the range of the related and threatened spotted owl (Strix occidentalis). Evidence shows the assorted threats posed by the invading barred species are only increasing. In response, biologists have recommended  culling operations to mitigate the negative effect of the barred on the spotted owl species.


The barred owl was first described by Philadelphia naturalist Benjamin Smith Barton in 1799. The species was named due to the varied directions the dusky markings take on their underside.
The barred owl is roughly intermediate in size between the larger Ural and the smaller tawny owl, but the structural features of its relatively short and decurved claws more so resemble the tawny species as does their dietary and habitat ecology. The spotted owl has been hypothesized to be within a superspecies with the barred owl. However, genetic testing reveals very early divergence (likely at or near their ancestor's entry to North America) between spotted and barred owls. A fossil species once called Strix brea from the early Pleistocene in California does little to resolve the ancestry of modern species, given its ambiguous relation to any living Strix. The fossil species was larger (more similar in size and slenderness to the spotted owl, albeit with a slightly smaller skull and geographically isolated from that species) and longer-legged than either the spotted and barred owls, and is now considered to be in a separate genus, Oraristrix. Pleistocene era fossils of probable barred owls are known from Florida, Tennessee and Ontario.


The subspecies of the barred owl vary mostly by region, with slight to moderate variation by coloring, size and extent of feathering on the toes. Although several have been described in the past, the barred owl may include only three subspecies, subsequent to the separation of the fulvous and cinereous forms.
S. v. varia (Barton, 1799): The northern barred owl. This race lives throughout the Northeastern United States and the Upper Midwest, ranging as far south as Oklahoma, the Carolinas and northern Georgia. It is also considered to comprise all western "invader" birds found as far west as California and British Columbia. However, genetic study of westerly birds show a substantial isolation, possibly up to the subspecific level, of the western and eastern populations of the northern owls, with an estimated divergence of around 7,000 years, perhaps indicating an unknown history of the species in remote forests of northern and central Canada (far west of what was considered their original distribution) that radiated more recently to comprise the western populations. This race is generally the typical mid gray-brown variety of barred owl. However, a paler variation with very washed out markings and a more pure whitish base color is known (in eastern Canada such as Quebec), formerly considered a race S. v. albescens, as well as darker and browner variation in northern Minnesota (formerly S. v. brunnescens). This race is fairly large (described as the largest race on average with the probable separation of the cinereous owl).  The wing chord and tail length may measure from 312 to 340 mm (12.3 to 13.4 in) and 215 to 230 mm (8.5 to 9.1 in) in males and 320 to 352 mm (12.6 to 13.9 in) and 224 to 257 mm (8.8 to 10.1 in) in females. One nominate bird had a tarsus length of 63.5 mm (2.50 in) and the culmen from the cere may measure 23.5 to 30 mm (0.93 to 1.18 in).
S. v. georgica (Latham, 1801): The southern barred owl or, alternately, the Florida barred owl. This subspecies is found in southern North Carolina closer to the coast along to broadly through Georgia and all of Florida. This is the smallest of the three subspecies on average. Known wing chord lengths can vary from 315 to 357 mm (12.4 to 14.1 in). Tail length is 205 to 231 mm (8.1 to 9.1 in) and the bill from the cere is 23 to 28 mm (0.91 to 1.10 in). Males in Florida were found to weigh from 681 to 800 g (1.501 to 1.764 lb), with averages in two samples of 718 and 744 g (1.583 and 1.640 lb), while two females weighed 850 and 875 g (1.874 and 1.929 lb), respectively. It therefore appears to show less pronounced sexual dimorphism than the northern barred owl race.
S. v. helveola (Bangs, 1899): The Texas barred owl. Comprises most barred owls found in Texas. The distributional range is considered to range as far north as Lee County, east to Chambers County, west to Kerr County and south to Nueces County. In this race, the ground coloration tends to pale gingery-cream and the back and head tend to be a pale brown ranging into an almost cinnamon color. The toes can vary from rather bare to slightly bristled. This race is similar to other barred owls in size, perhaps averaging marginally smaller than those in the nominate race, but its bill and feet are larger on average than the preceding two races.


The barred owl is considered somewhat subdued and drab in coloration compared to the sometimes rich coloring of other sympatric owls. Overall, this owl is greyish-brown or brown. The brownish color extends from the head to the back. Barred owls are scalloped with white bars on the mantle and the back, bearing as well some whitish spotting on the wing coverts. The underside has a pale creamy gray-brown base color (ranging into dirty white in the palest individuals) overlaid about the throat and upper chest with horizontal, slightly crescent-shaped barring (hence its common name), while the belly is boldly streaked in a vertical pattern. The streaking is usually blackish, dusky brown, or sometimes rufescent- (reddish-) brown. The head is fairly large (although not especially so for a species in Strix) and rounded with no ear tufts. The facial disc is pale grayish-brown with darker yet subtle concentric lines. The bill is pale straw-yellow (occasionally showing a mild greenish tint) while the cere (a bare structure at the base of the beak) is "horn-colored". Its eyes are of a blackish-brown color, this being the only true owl of the eastern United States which has brown eyes; all others have yellow eyes. The eyes may appear intensely black in the field and, although large, are fairly closely set.
The barred owl has well-developed eye anatomy. As is typical of owls, their ocular anatomy is quite distinct from diurnal raptors especially in terms of their photoreceptor cells, as they have a very large number of rod cells in their quite sensitive retina. However, their pecten oculi is smaller relative to the size of their large ocular globe (other large owls are known to have similar pecten proportions). The vision in limited or almost no light during a laboratory study of a barred owl was found to be similar to that of other owls, including the long-eared owl (Asio otus) and the barn owl (Tyto alba). The tarsi and toes are feathered up to the dark gray, black-tipped talons. These feathers are more sparse and bristled in the southern races. On individuals with bare sections of their toes, the toes are yellowish-gray in color. The flight feathers are barred with whitish buff and brown while the tail is brown or grayish-brown with 4–5 whitish bars. Young barred owls with their second set of down feathers are fluffy brownish-white, with indistinct darker barring on their head, back and mantle. They quickly become juveniles which resemble adults but have less distinct markings (especially about the head and neck), more buff coloring overall, often some remnant down, pinkish skin and a pale, blue-green cere. Also the tail at this age may have as many as seven bands (though sometimes have four like adults). Full adult plumage is obtained via molt after about a year as well as adult bare part characteristics. A study of tail molt in Washington showed that molt tends to occur relatively quickly, and that young individuals are difficult to age by state of molt alone. Southern barred owls tend to be darker and slightly smaller than northerly ones. Rare captive and wild barred owls with albinism have been described and are pure white but tend to retain their brown eyes.
The barred owl is a large species. The adult measures anywhere from 40 to 63 cm (16 to 25 in) in length while the wingspan may range from 96 to 125 cm (38 to 49 in). The wing area (measured by square centimeter relative to the body mass) is quite intermediate among American owls, with the wing loading being lower than larger, but proportionately small-winged larger owls and even than some smaller owls. The barred has high wing-loading. Wing-loading is related to hunting technique, with higher wing-loading owls typically hunting from a perch, with only a brief flight necessary to obtain food, whilst lower wing-loading owls often hunt their prey from active flight.  As is the case in most owls, the various wing feathers of barred owls are uncharacteristically soft and bear a comb-like shape, which in turn renders their flight functionally silent during their hunts. Like most birds of prey, the female is larger than the male barred owl, sometimes described as reverse sexual dimorphism (due to the fact that males average larger than females in most non-raptorial birds).
Among standard measurements, the wing chord of grown males varies from 303 to 340 mm (11.9 to 13.4 in), with an average from three sources of 326.2 mm (12.84 in), the tail may measure from 182 to 250 mm (7.2 to 9.8 in), with an average of 219.6 mm (8.65 in) and the culmen from the cere may measure from 22 to 27 mm (0.87 to 1.06 in), with an average of 24.3 mm (0.96 in). Meanwhile, for the female, the wing chord may range from 318 to 357 mm (12.5 to 14.1 in), averaging 335.8 mm (13.22 in), the tail from 204 to 257 mm (8.0 to 10.1 in), averaging 223.3 mm (8.79 in) and the culmen from the cere 20 to 30.7 mm (0.79 to 1.21 in), averaging 25.1 mm (0.99 in). Sexual dimorphism is particularly pronounced in barred owls by body mass as males within a population are sometimes a third lighter in weight. In the nominate subspecies (S. v. varia), average weights for males have been reported as 621.9 g (1.371 lb) (sample size 12), 632 g (1.393 lb) (sample size 20) and 681 g (1.501 lb) (sample size unknown) in three samples. The weight range for adult males is known to vary from 468 to 812 g (1.032 to 1.790 lb). The considerably larger female of the nominate subspecies has been reported to average 801 g (1.766 lb) (sample size 24), 872.6 g (1.924 lb) (sample size 14) and 909.5 g (2.005 lb) (sample size unknown). Altogether, fully-grown female barred owls may weigh from 610 to 1,150 g (1.34 to 2.54 lb).


The barred owl is a powerful vocalist, with an array of calls that are considered "spectacular, loud and emphatic". Calls probably carry well over 0.8 km (0.50 mi). Its usual call is a series of eight accented hoots ok-ok-ok-ok-ok-buhooh, or the "typical two-phrase hoot" with a downward pitch at the end. The most common mnemonic device for remembering the call is "Who cooks for you, who cooks for you all." Due to its best known call, the barred owl is sometimes colloquially referred to as Old Eight-Hooter. At 80% of study posts in Virginia, barred owls responded to playback of this call. A further call is the "ascending type" or the "legato" call, a series of variable notes ending in oo-aw or hoo-aah. At least two other variations on the legato/ascending call are known. 56% of studied owls in Virginia engaged in the ascending type call but 36% uttered only the closing notes. The isolated hoo-aah, sometimes called the "inspection call", was the most common song type in north Florida and the most likely to heard during daylight. Several other calls, although some are not dissimilar variations on the main calls, are known. Some of these vary into cackles, hoots, caws and gurgles, at times described as "sudden demonic laughter", "cat-like screams" and "prolonged outbursts of cackling" and seem to be, among Strix species, an idiosyncrasy endemic to the barred owl.
Another call type is the "mumble", a grumbling, slurred and subtle err-ERR-err, also an up-and-down "twitter" call at a high pitch. When agitated, this species will make a buzzy, rasping hiss about three times in three seconds, repeating every 10–30 seconds, and will click its beak together forcefully. Females and juveniles beg with high scratching skreeechch notes. The voice of the two sexes is similar, but the female has a higher-pitched voice with longer terminal notes. Of calls, 87 to 94% are identifiable to sex per one study. While calls are most common at night, the birds do call during the day as well, especially when provoked by human playback or imitation. They are more responsive than any hawk in the east to playback of calls of their own species. The barred owl is noisy in most seasons but peak vocalization times for barred owls tend to be between late January (in Florida) and early April (in Canada). Two seasonal peaks in vocalizations, one right before breeding and another after the young have dispersed, was detected in Connecticut, with peak vocalizations on nights with extensive cloud cover. Peak times for vocalizations are between 6:00 pm and 6:00 am, with the least frequent vocalizations around mid-afternoon.


The barred owl is distributed throughout most of the eastern United States, as well as much of southern Canada. They are found as far northeast as much of Nova Scotia (western two-thirds), New Brunswick and Sept-Îles, in much of Quebec, up to Lake Mistassini, and Ontario, up to Moosonee. The barred owl has been recorded as ended up as far north as central Labrador, though the species is not yet confirmed to breed in the province. The barred owl ranges in every part of the eastern United States continuously from northernmost Maine down throughout New England, the Mid-Atlantic states, much of the Midwest, the Southeast United States and all of Florida. They are found to as far west without substantial gaps to the limits of western Minnesota, easternmost South Dakota, the southeastern corner of Nebraska, the eastern half roughly of Kansas, most of Oklahoma and east Texas to as far west as Cisco and Burnet. Arguably and discontinuously from Texas, the species may range into central and southern Mexico but these populations are now often considered a separate species. These initial parts of the range in the eastern and central stretches would be considered as where the species is “native”. A wandering barred owl was once seen flying over Lake Michigan 48 km (30 mi) from the nearest land.


The remaining parts of the range are considered where the barred owl introduced itself in the last century or so. The historical lack of trees in the Great Plains presumably acted as a barrier to the range expansion, and recent increases in forests broke down this barrier. Increases in forest distribution along the Missouri River and its tributaries provided barred owls with sufficient foraging habitat, protection from the weather, and concealment from avian predators. This allowed barred owls to move westward, initially solely along other forested river corridors (e.g. the Yellowstone and Musselshell), but increases in forests in the northern Great Plains decades later would allow them to connect their eastern and western distributions across southern Canada. These increases in forests were caused by European-American settlers via wildfire suppression and ceasing the fires historically set by Native Americans, as well as by increased tree-planting.
In Canada, the barred owls with range expansion now range through southern Manitoba (excluding the southwest corner), a broad section of south-central Saskatchewan, and east-central and nearly all of western Alberta, now up to High Level. The barred owl has been present in Manitoba at least since 1886, Alberta since 1932 and Saskatchewan since 1948. However, a study in Alberta has shown that barred owls have likely been present for no less than 100 years. This owl species currently ranges through much of British Columbia, where they have been expanding their range since at least 1943, including Vancouver Island and as far north as Fort St. John. The barred owl has had a further northward expansion in the west to southeastern Alaska (Skagway to Ketchikan) and extreme southwestern Yukon. In the western United States they also range into northwestern Montana and northern Idaho. Barred owls were first verified in southwest Montana in 1909 and in northwest Montana in 1921 (although reports of the species may date back to the 1870s) but not in Idaho until 1968. Of unknown origin, Barred owls have been seen in Colorado since around the turn of the 20th century. They range broadly in eastern and western Washington (reached by 1965) and western Oregon (reached by 1972) (mostly along the forested corridors hugging the montane areas of the Cascade, Olympic and Blue ranges), and northern California (reached by 1976), now down to the Redwood National Forest, the Sierra Nevadas and outer San Francisco.


The habitat used by barred owl is largely old deciduous, mixed forests and, occasionally, coniferous forests. Old growth forests are preferred due to more extensive potential nest sites, less lower-branch density to impede hunting (and perhaps superior structural complexity to aid hunting), greater security from mobbing and perhaps greater thermoregulation. They are often found in bottomland hardwood forests in the largest swath of the native breeding range, often (particularly from Virginia south and west) with deep, dark stands of oak, gum and cypress. Secondary habitat, often used during foraging forays in the south, are often oak savanna or cabbage-palm areas. Regardless of area, some variety of water is frequently present, including riparian areas or swampy ground. Closed canopy forests were preferred in a study from Oklahoma (62.8% of habitat used), followed by fallow agricultural fields (10.6%), wetlands (8.1%) and open terrain (6.2%). The latter three were visited during hunting forays, and wetlands and open terrain areas were not used outside of the breeding season. Along the Atlantic coast area from New England to New Jersey, barred owls are often found in mixed swamps areas with cedars, seldom wandering to adjacent wetlands or farmland. The species may be at home in wooded areas in mountainous regions. More upland wooded habitats, often in mixed woods containing hemlock, alder, poplar, pine and oak, are typical in the northern part of the range. A study in northern New Jersey found at least 15 species of both conifer and deciduous trees were routinely used for differing purposes. In Michigan, barred owl habitat usually consists largely of some combination of hemlock and maple trees, with mixed forest usage being use disproportionately to its prevalence in the environment. Large oak stands were preferred in Minnesota, a bit ahead of mixed forest and far ahead of white cedar swamps and other habitat types, which were either too dense, too open or had too few attractive nesting sites.
Barred owls are not confined to extensive forest, also dwelling extensively in semi-open wooded areas, locally in large parks with mature trees, and in forest adjacent regions recently logged. Recent studies show suburban neighborhoods can be ideal habitat for barred owls, and the species may be considered a local synanthrope. Using transmitters, scientists found that some regional populations, such as in Charlotte, North Carolina, increased faster in the suburban settings than in old growth forest. A factor of this suburban success may be easily accessible rodent prey in such settings. However, for breeding and roosting needs, this species needs at least some large trees and can be locally absent in some urban areas for this reason. The increased offspring offset the death rate due to impacts from cars, other types of collisions and disease. Similarly, in Piedmont, South Carolina, productivity of the owls was higher in suburban areas and they comprised 41% of the territories of the local owls but various sorts of anthropogenic mortality were seemingly higher. In suburban areas of Ohio, 41.4% of barred owl range was forested, 29.8% was low-density residential areas and less than 15% was pasture. On the other hand, studies from the Northeastern United States, such as in New Jersey, found barred owls breeding mainly in plots of old-growth woodlands, and rarely successfully breeding in peri-urban areas, in part because of competitive and predatory displacement by great horned owls. Furthermore, a study in North Carolina showed most barred owls appear to favor areas with at least 86 to 370 ha (210 to 910 acres) of woods but did not seem to be affected by the presence of roadways.
In the Pacific Northwest, they can be quite adaptive to secondary forests. On the other hand, in Ontario where the barred owl is native, secondary forest seemed to be largely avoided per a study. In the recent western part of the range, barred owls often dwell in mixed wood areas, often where there are lowland stands of balsam poplar, trembling aspen and white spruce, occasionally but not commonly in pure conifer boreal stands. Barred owls in California preferred stands of red alder. More so confined to inland areas, as in eastern Washington, Idaho, Manitoba and Montana, they prefer Douglas fir, ponderosa pine, paper birch, burr oak and western larch. In north-central Alberta, the use of old growth forest was far more prevalent than its occurrence in the wild. In the Cascades Range of Washington, barred owls usually dwell in areas with more grand firs, taller and more diverse tree heights, more enclosed canopies, higher numbers of trees per acre and less ground cover. In Saskatchewan, barred owls preferred areas with a minimum of 66% forest cover.


The barred owl, like most owls, is largely adapted to nocturnality. Between 5:00 am and 8:00  pm, juvenile barred owls were recorded to sleep an average of 28% of each hour. Peak times in Minnesota were found to be right after sunset and just before dawn. Nonetheless, they are not as fully nocturnal as many owls and rank around 6th amongst 19 regular North American owl species for the regularity of their activity outside of nightfall, especially in particular circumstances such as when a rival or a human impersonator is emitting barred owls calls or whilst hunting. Often daytime activity tends to be early in the morning or around dusk but potentially at any time (overcast days being preferred). This species often spends the daytime hidden away in dense foliage of a tree, often at minimum 5 m (16 ft) above the ground, but sometimes also roosts in branch close to a broad trunk or in a natural tree hollow. Roost tree heights in Minnesota was typically 8 to 12 m (26 to 39 ft) while, in Illinois, they were up to 9 m (30 ft). Recently fledged owls sometimes roost in tall grass, usually after falling from the nest tree.
Roost site selection may be partially dictated by thermoregulation, as in spotted owls, with shadier roosts likely to mitigate heat stress. They seldom rely on camouflage, instead often flying at the least disturbance and not allowing close approaches, making them potentially difficult to observe. Yet, on the other hand, they can be surprisingly tame and seemingly curious of people in the wild; further they are considered "as mild and engaging" as a predator can be. Barred owls are regularly subject to mobbing by small birds, from several small passerines to corvids and woodpeckers, and mammals when discovered by them during the daytime, and such situations may lead to them being attacked by diurnal birds of prey. There are some records of barred owls engaging in allopreening, presumably between pairs, with each other in the wild. They are skilled and silent fliers and frequently use routine forest flyways with open understory and low branch densities.
Like most species of owl in the Strix genus, the barred owl tends to be highly territorial regardless of the time of year. The territories are claimed by singing from different perches, often near the perimeter of its perceived home range. The boundaries are almost always well-maintained by barred owls and are generally stable from year to year and even generation to generation. Territory sizes have been determined via radio telemetry. The average territory size of 13 in Minnesota was 273 ha (670 acres), of 7 in Michigan it was 282 ha (700 acres) and of 10 in Wisconsin was 337.9 ha (835 acres). Another Minnesota study found pairs to occupy a mean of about 226 ha (560 acres) in mixed hardwood-conifer woods. Pairs in an Oklahoma study were reportedly found every 110 to 165 ha (270 to 410 acres). The mean territory size from 10 studies were estimated from throughout the range. In this study, the breeding season mean area was calculated at 256.7 ha (634 acres) in males and 297.8 ha (736 acres) in females; whereas the means in nonbreeding season were 900.4 ha (2,225 acres) in males and 536.2 ha (1,325 acres) in females. Overall, the annual mean home range for males was 782 ha (1,930 acres) and for females was 538.7 ha (1,331 acres). The breeding range's mean home size in Washington was 321 ha (790 acres), while it was 971 ha (2,400 acres) in the non-breeding season.
The ranges of pairs overlaps in the breeding season, at 87–95% range overlap, but decreases down to 45% after hatching. In a Florida study of barred owls, territorial responses, including several duets, by a pair were found to be provoked by researchers playing calls of both "stranger" owls and recordings of owls that were neighbors to the pair being tested. The aggressive response even to known neighbors in this study is unusual. In tawny owls in a study from Italy, for instance, they responded mildly or not at all to the calls of neighboring tawny owls known to them but with great aggression to the calls of "stranger" owls. Due to its rather stolidly territorial nature, the barred owl is not normally a migratory species. Claims in the past of "rather impressive" flights in New England in the past were lacking in verifiable details. Of 158 banded recoveries in the northern part of the range, movements during winter were found to cover no further than 10 km (6.2 mi), while all those recovered in Saskatchewan and Alberta scarcely moved at all. There is little to no evidence of nomadic behavior as has been recorded in several other owls in the north.


Barred owls are opportunistic predators of the woodlands. Like the tawny owl, the barred owl usually hunts from a perch. During hunting efforts, they glide briefly from perch to perch until prey is detected. The barred owl has incredibly large eyes that capture as much light as possible, allowing for better night vision. Attacks may be carried out merely 6 to 10 m (20 to 33 ft) away from the prey due to the effectiveness of the silencing wing feathers. The barred owl, especially compared to the predominantly arboreal prey of the spotted owl, usually prefers to target small animals that are terrestrial. However, barred owls will also flush and capture night-roosting birds, and capture bats on the wing as well. Daytime hunting has been reported several times, although peak hunting time is typically shortly after sunset. Although they usually hunt within woodlands, they not infrequently hunt in open terrain, more typical of the hunting areas of a bird like the long-eared owl. Cases of snow-plunging have been verified for barred owls, allowing them to capture prey like voles in subnivean zones that they use as hidden snow tunnels during winter, a hunting method once thought particular to great grey owls. While hunting squirrels in the Foothill Model Forest of Alberta, barred owls were seen to make several passes before succeeding. Hunting on the ground is usually done to obtain foods such as invertebrates or amphibians. These owls may wade into water to capture fish and may do an unusual amount of aquatic, for any Strix species or North American owl, foraging via wading into shallows.
Due to its relatively modest foot size, it does not usually take particularly large prey. However, owls in general have proportionately larger feet and more powerful grips than similarly sized diurnal raptors, while the physiology of the daytime raptors differs. While the mechanism of the killing feet overlap, owls kill mainly with constriction and sacrifice velocity with their physiology while diurnal raptors have higher velocity and kill mainly by trauma inflicted by their enlarged talons. A majority of prey of barred owls is eaten outright but, with large prey, the barred owl may eat the head first and then return to consume the remainder of the body. Cases of owls of any variety scavenging on carrion are generally rare, but at least three instances of carrion-feeding by barred owls have been observed, more recently eating deer and squirrel roadkills on a remote camera in North Carolina. The pellet of the barred owl averages about 3.5 cm (1.4 in) in diameter and 7.2 cm (2.8 in) in length.
The barred owl has been known to consume a diversity of animals from different taxonomic classes. Primarily, these owls live off of small mammals. Other vertebrates are rarely neglected though, especially birds and amphibians, but also occasionally reptiles and fish. For an owl its size, the barred owl also consumes a large amount of arthropods and other invertebrates. One study from a wide swath of the range found that among 2234 accrued prey items, 76% were mammals, 15.8% were invertebrates, 5.8% were birds and 2.5% were other vertebrates. In four other studies from different parts of the distribution, the mean balance of mammals in diet was around 64.9%, birds at around 13.4%, invertebrates at around 11.4% and different classes of vertebrates (mostly amphibians) at around 10.3%. A compilation study that included a total of 7077 prey items using all methodologies, 71.9% were mammals, 9.5% were birds, 0.6% reptiles, 6% amphibians, 1.89% fish, 1% earthworms, 0.2% gastropods, 6.5% insects and 2.4% crayfish. Barred owls tend to focus on fairly small-sized prey, although are capable of attacking larger than usual prey in infrequent cases. The mean size of prey taken is seldom estimated in the barred owls’ eastern range, although one study estimated mean size of prey in the general east was 33.5 g (1.18 oz). Many more studies have estimated mean prey masses in westerly areas of sympatry with spotted owls to understand how their diets may conflict. Different studies from the west (mainly Washington and Oregon) have variously estimated the mean prey sizes for barred owls at 47.7 g (1.68 oz), 56.1 g (1.98 oz), 60.2 g (2.12 oz), 103.5 g (3.65 oz) and 123.6 g (4.36 oz).


The predominant small mammals available in forest and woodland edges are generally small rodents, so the barred owl, like other Strix owls, most often relies on rodents as the primary type of food. Preferred rodents to be taken are voles, mice of the genus Peromyscus and assorted rats, including non-native Rattus species as well as unrelated native types like cotton rats, rice rats and woodrats. These all share with barred owls a penchant for nocturnality and crepuscular habits (although many voles are more correctly considered cathemeral) While during other seasons, the diet of barred owls can be fairly diverse, the winter diet may be almost wholly rodents. This was the case in winter in Montana, where 97.6% of 1153 prey items were montane voles or meadow voles, with a possible slight mixture of other voles. The diet of barred owls in a much smaller study near Urbana, Illinois during winter was less homogeneous but still led by rodents, especially the meadow vole (32.3%) and white-footed mouse (23.5%). A winter food study in Essex County, New Jersey found that among 118 prey items, meadow voles comprised a great majority of the prey, at 91.5% of the balance.
An unusual lack of diversity in barred owl pellets was found in several years of possibly aseasonal study in Ann Arbor, Michigan where of 777 prey items, 83.3% were meadow voles. At Edwin S. George Preserve near the University of Michigan, the summer diet was also heavily rodent based, as among 146 prey items 37.9% were white-footed mice, 22.6% were southern bog lemming and 6.84% were meadow voles. In a somewhat larger Michigan study, the North American deermouse, lead the prey at 34.9% of 321 prey items. In Minnesota, the barred owl was counted as one of the leading causes of mortality of prairie voles. Studies of the barred owl diet in 6 urban metropolitan areas of British Columbia found that the diet was dominated by young rats of the invasive Rattus genus, comprising 52.8% of 688 prey items, well ahead of native Townsend's voles, which were secondary at 19.2% of the diet. The average weight rats taken by owls were clearly juveniles, estimated to average 103 g (3.6 oz), although several could be anywhere from infant rat to adult rat sizes, i.e. about 25 to 300 g (0.88 to 10.58 oz). The mean size of black rats taken in Oregon was 250 g (8.8 oz), indicating that here large adults of this species were selected. Beyond the typical more meadow-dwelling voles and woodland edge-dwelling native mice, larger and more forest dwelling rodents of different varieties can be of variable import. Numerous woodrat species may be taken and may provide a hearty meal to a barred owl, at a mean body mass when taken (in Oregon) of 285 g (10.1 oz) for unidentified species.
In different areas, barred owls may regularly hunt the diverse members of the squirrel family, despite their general penchant for diurnality. Smaller squirrel varieties are usually focused on when hunted as supplement prey, such as chipmunks, averaging about 83 g (2.9 oz) among the different species they prey upon, and pine squirrels, which average about twice as large as chipmunks. Usually juvenile specimens are focused on when taking the larger Sciurus tree squirrels, at least in summer, but presumably a mixture of yearling and adult Sciurus will be taken during winter. The mean weight of western gray squirrels taken during the breeding season in Oregon was 450 g (16 oz), against a mean adult weight of around 770 g (1.70 lb). The issue of temporal activities is less pertinent to the predator of flying squirrels, which are nocturnal. All studies of the diet of barred owls in Pacific Northwest show the importance of the northern flying squirrel to their diet. This flying squirrel was found to comprise from about 10.9% to 20% of the diet of barred owls (either as the most or second most important prey species) and, with a mean weight of 134 g (4.7 oz) when taken, they comprised up to 25.6% of the food biomass for this owl species. In Green Ridge State Forest in Maryland, although not numerically the most important prey family compared to unidentified cricetids and shrews, the southern flying squirrel was the most often identified prey species for barred owls. Beyond the aforementioned rodent prey, more infrequently rodent prey can including various other crecetid rodents, pocket gophers, mountain beavers (average weight when taken of up to 550 g (1.21 lb)) and jumping mice. The largest known rodent prey of barred owls are adult muskrat, which were estimated to weigh 1,169 g (2.577 lb) when taken.
The other primary mammalian prey types are the shrews and the moles. At least a dozen species of shrew and most North American species of mole are known as prey of the barred owl. 12.8% of 7077 total prey items from across the range were shrews or moles. A small sample of prey in Michigan was led by the very small masked shrew, which weighs around 4 g (0.14 oz), at 25% of 34 prey items. A much larger shrew, the northern short-tailed shrew at around 21 g (0.74 oz), was the leading prey in Glenwood, Minnesota at 35.8% of 81 prey items. This prey species also is taken quite regularly in several other parts of the range, as well as a closely-related species. Assorted other shrew species and the smallest of the world's moles, the American shrew mole are regular supplement prey elsewhere, especially in the Pacific Northwest. The most frequently taken single prey species through the Pacific Northwest, at 11.8% of 4299 total prey items of barred owls, was the 56 g (2.0 oz) coast mole. Usually, moles are secondary if relatively hearty prey elsewhere in the range. Secondary prey that is heartier still can include several species of cottontail rabbits 3.2% of 7077 prey items from across the range for barred owls were rabbits or hares. As for the often sympatric eastern cottontail. Even larger prey (perhaps the largest verifiable prey of all for barred owls) is the regularly taken snowshoe hare. The mean weights of these hares taken by barred owls in the Pacific Northwest was estimated at 1,000 to 1,200 g (2.2 to 2.6 lb) but the largest hare specimens killed by the barred owls were estimated to weigh about 1,400 g (3.1 lb).
Bats are infrequently reported as prey in most of the range but an unusually close association was detected in Valdosta, Georgia, where most of the prey, 65% of pellet contents and 37 total bats, were southeastern myotis. Barred owls are also known predators of both eastern spotted and western spotted skunks, the latter estimated to weigh 606 g (1.336 lb) when taken. Much larger mammals are sometimes recorded in the foods of barred owls, but there are few details known about the age, condition or circumstances (i.e. they may have been consumed as carrion or, perhaps more likely, young or infirm specimens were taken). Some such prey species recorded have included the Virginia opossum, the North American porcupine, the striped skunk and the domestic cat. Adults of all these species are known to count amongst the prey of great horned owls which are better suited than barred owls to take particularly large prey given its more robust morphology.