During daytime, long-eared owls tends to roost in an upright position on a branch, not infrequently close to the trunk, oftentimes within dense foliage. In winter often stays close to the same tree or grove of trees (i.e. in parks, large gardens, or cemeteries). Usual when approached, the owl will freezes with its body stiffly upright, eyes closed to narrow slits and ear tufts erect. This is called the “tall-thin position” and is common to at least a couple dozen species of typical owl. If approached closed, the owls will alternately open and close their eyes (apparently having stirred but trying to fool potential predators into thinking the owl is still at rest), finally lowering ear tufts, fluffing body plumage and flying to another roost. Unlike most owls, which show a tendency towards territorial behavior on a fixed range year-around when possible, long-eared owls in the non-breeding season are often prone to occur in aggregations of owls while roosting. Such grouping may not uncommonly include up to 6 to 50 owls at times, with a European record of about 150 owls at a single roost. Even other migratory owls in the temperate zone do not tolerate each other as closely as do long-eared owls, with short-eared owls seemingly only forming aggregations when food supplies are exceptionally high, while social roosting in long-eared owls seems to occur regardless of local prey numbers. Long-eared owls tend to roost in the depths of the "darkest stands of trees" in order to conceal their presence, though they prefer being close to forested edge to allow access to hunting over more open ground. A study in the New Jersey Meadowlands area  showed that roosting owls had a strong fidelity for certain trees, particularly conifers such as cedars where the main truck is large obscured from view and a grouping of at least 2-3 closely clumped trees occurs. Roost height in the New Jersey study was at 3 to 15 m (9.8 to 49.2 ft) or occasionally higher. In New Jersey, different roosts were preferred each year and in the local heavily modified environment, the owls become partially habituated to human activities. However, approach at closer than 3 to 4 m (9.8 to 13.1 ft) away usually caused them to flush. Departure of owls for nighttime hunting would generally occur between 40 and 49 minutes after sundown. Studies in the Moscow region of wintering roosts were done over 10 years, with 12 communal and 14 solitary roosts found. The communal roosts included up to 16 individuals per winter, with a mean of 9.9. Overall, the average in Moscow per roost site was 2.1 owls. Vole numbers the preceding year were likely the causes of numeric variations in years here while wind and snow avoidance were key in characteristics of roost sites. Extraordinarily large roosts were the norm in a study in Stavropol, Russia, where the general roost area could host from 80 to 150 individuals each winter over 4 years, with 93.7% of the roosts located in coniferous trees. In Milan, Italy, from 2 to 76 long-eared owls were observed per urban roost site. Here, nighttime observation showed that owls individually would depart the roost at peak during the darkest part of nighttime. A majority of the Milan roosting owls did not fly toward urban areas instead flying to suburban fields and forest where prey is more easily encountered. The reason for roosting in aggregations seems to be at least in part to mitigate predation risks.


Long-eared owls may divide their hunting into phases, the first stopping around midnight, the second beginning some point after midnight and ending an hour before sunrise. While hunting, they tend focuses on the edge of woodlands, hedgerows and open spaces with rough grassland, and over young trees and open ground of all kinds. They hunt mainly on the wing, flying low and fairly slowly, often being quite low to ground, i.e. only  around 150 cm (59 in). More often than visually finding their prey, it is thought that long-eared owls most often audibly detect the rustling of their intended food. In lab settings, long-eared owls were considerably more skilled at finding mice by sound in more or less complete darkness than tawny and barred owls (Strix varia), and in some American experiments even outclassed the auditorily-acute barn owls in this regard. Once prey is spotted, the long-eared owl's flight suddenly stalls, then they quickly drop with talons spread to pounce on prey that is perceived, or especially, that comes out into the open. Habitat may be perhaps even more key than prey numbers to the selection of hunting grounds. Often when prey numbers are more ample in timbered areas nearer the roost or rich marshy areas in the vicinity, the long-eared owls will still often come to more prey-poor areas such as old fields so that they can detect prey on open ground. The footspan of a long-eared owl, including claws, reaches on average 11.3 and 12.5 cm (4.4 and 4.9 in) in males and females, respectively, which would be large for a diurnal bird of prey but is quite small for an owl of its size, given the physiological differences in the way different birds of prey tend to kill their prey. While acciptrid raptors tend to kill by stabbing with their talons through vital organs, owls are more likely to constrict their prey to death, so tend to have proportionately larger, more robust feet. In other medium-sized owls, the footspan in tawny owls and barn owls respectively averages 13.4 and 13.2 cm (5.3 and 5.2 in) in between the sexes (notably footspan seems to be a fairly reliable predictor of body mass of an owl as well). Prey capture by long-eared owls was studied and compared to tawny owls in a European experiment. The two owl species caught mammals and beetles caught in similar ways but the long-eared owls shied away from flying sparrows and would only capture the sparrows when they perched (though the tawny did not avoid flying sparrows, it too would only capture the prey when perched). Long-eared owls either disregarded or killed but did not eat amphibians, while tawny owls did catch and eat amphibians when they were available. Occasionally the tawny owls would attack fish whilst one long-eared owl caught but did not eat a fish. The European study further revealed that several owls of different species ate bits of plant and did not appear to do so out of food deprivation or hunger.
Taken as whole, the global population of long-eared owls may appear to have a widely varying diet. One study accrued information from 312 studies from around the species’ range. In total 478 prey species were found to be described, of which 180 were mammal species, 191 were bird species, 83 were assorted invertebrate species, 15 were reptiles, 7 were amphibians, and reportedly just a couple fish species. This included a total of approximately 813,033 prey items having been reviewed. However, on closer inspection, the long-eared owl generally appears to be something of a dietary specialist. It usually takes primarily, often nearly entirely, small mammals, e.g. rodents, as food in almost every part of its range. Usually a broad picture emerges that between 80 and 99% of the diet consists of mammals, averaging 94% in one estimate for all of Europe. However, in warmer, insular or more urbanized environments, a greater percentage or, rarely, even a majority of the diet can locally be non-mammalian prey. Mean prey sizes have been studied extensively and are almost always fall within a very narrow range. In Europe, the mean estimated prey size overall was 32.2 g (1.14 oz). Meanwhile, in North America, mean prey sizes have varied between 30.7 and 37 g (1.08 and 1.31 oz) in two estimates. In general, throughout their range, the mean size of prey is generally encapsulated between 20 and 50 g (0.71 and 1.76 oz), usually well under 40 g (1.4 oz), and only in cases where long-eared owls, perhaps through lessened competition, has regular access to prey weighing 60 to 100 g (2.1 to 3.5 oz) or more, may the mean prey size range uncommonly reach 50 to 60 g (1.8 to 2.1 oz). Cases of exceptionally large prey are mentioned where they occur below.


The long-eared owls derives almost of its food energy from rodents. Among this order, they are usually associated with a single group, the voles. The life history of the long-eared owl is inexorably linked to voles. Voles, members of the family Cricetidae and subfamily Arvicolinae, are often numerous, small-to-medium-sized rodents with relatively short tails. In Europe, especially, the long-eared owl can be considered a specialized vole hunter. Out of 86 prey studies in the continent, in about 69% voles made up more than half of the prey. In particular, in the region of central Europe, a little over 82% of 57,500 prey items was made up of voles. Where a variety of voles are available in Europe, long-eared owls show a preference for the most gregariously inclined common vole (Microtus arvalis) over the less sociable field vole (Microtus agrestis). In central Europe, 76% of the diet was compromised by the common vole species alone. More specifically, in the largest known study from Germany, of 45,439 prey items in the regions of Berlin and Nordharz, common vole accounted for 72%, with the field vole and tundra vole (Microtus oeconomus) collectively another 5.5%. Another large representation of the common vole was in Slovakia, where they made up 84.1% of the diet (27,720 out of 32,192 total prey items). In different years in Slovakia, common voles may range from as much as 92.4% to as little as 57.2% depending on vole numbers. Locally, such as in former Czechoslovakia and in western Ukraine, about 94-95% of the diet may be common voles alone (of 4,153 and 5,896 prey items, respectively). The dietary association with the common vole generally continues to most areas of European Russia, such as Moscow. At times, such as indicated in Moldova, long-eared owls are capable of culling as much as 50% of the common vole population and it was opined that the voles would easily become pestilent to humans if not naturally controlled. Like many voles, common voles are subject to population cycles. In accordance with the cyclic nature of vole populations, the local numbers of long-eared owls can rise and fall sharply. In low vole years, they tend to lay fewer eggs and feed fewer young, and may not attempt to breed at all. In high vole years, they generally lay and hatch more eggs and rear more young. While incubation starts with first egg, only the oldest siblings may be feed in low food years. Generally various species of mice are eaten in poor years for common voles but appear to be an inefficient substitute (at least in more northerly climes) based on the owls’ lower breeding rates. Apparently, common voles at times may collectively shift in temporal activity into more diurnal activity in what may be an attempt to mitigate heavy owl predation (especially as basically all European owls tend to hunt them), although several diurnal predators are nearly as specialized predators of them as well. Evidence has indicated that common voles are altering their life cycles with unknown long-term results due likely to global warming. It is likely that the long-eared owls of the region are to be effected by this but it is uncertain exactly what the resulting effect will be.
In some parts of Europe, common voles are at times not found or are locally infrequent or rare, especially on large islands, Scandinavia and some parts of the southern reaches, such as the Iberian Peninsula, Italy and Greece. Therefore, long-eared owls live mostly on different prey species. Supplemental or, occasionally, primary prey when voles are less common are murid rodents, especially the commoner genera such as Apodemus or field mice, Mus or house mice and, occasionally, Rattus or typical rats. In Scandinavian studies, common voles were still the main prey in Finland where distributed (and outnumbered field voles in the owl's diet four-to-one) and partially in Denmark (where foods were split between the two commoner vole species and field mice) but are not in Sweden and Norway. In Sweden, where common voles are not found, field voles were the main food, making up 65.2% of 13,917 prey items, followed by Apodemus field mice species, which were a further 25.3%. In Norway, 3,431 prey items were primarily field voles (42.75%), Apodemus species (12.64%),  tundra voles (12.35%) and bank voles (Myodes glareolus) (12.06%). In the British Isles, primary prey switched between field voles (46.6% of 1,228 prey items in the Peak District and 79% in southern Scotland) and Apodemus mice, most especially the wood mouse (Apodemus sylvaticus), (75.6% of 1,772 prey items pooled from different parts of England and 69.5% of 1,373 prey items in Ireland, where native voles are entirely absent). In warmer areas, the long-eared owls may vary in diet depending on local prey composition. In Spain, voles, including common voles, Mediterranean pine voles (Microtus duodecimcostatus) and Lusitanian pine vole (Microtus lusitanicus), collectively made up 76.4% of 6,945 prey items in the central part of the country while on the Ebro in northern Spain, the Algerian mouse (Mus spretus) was dominant, at 69.5% of 846 prey items. Overall, in 7 studies from assorted Spanish locations, wood mice and Mus species were the most regular prey (together accounting for just under 60% of the sum total prey items). Many studies in Italy show that the species is not as much of a specialized feeder in the country with considerable regional variation in prey preferences. Inclement weather in particular, including any kind of precipitation or high winds, seems to cause Italian long-eared owls to increase the diversity of prey that's routinely caught. In some Italian studies, Savi's pine vole (Microtus savii) were the main food, at Prignano Cilento where they made up 60.4% by number and 61.6% by biomass. In others, the wood mouse was the main food, such as Cremona, at 59.1% of 1,482 prey items. An unusual close prey association was noted in northern Italy, where access to landfills allowed them access to exceptionally large prey, brown rat (Rattus norvegicus), with juvenile rats caught that weighed on average 140 g (4.9 oz) and sometimes weighing up to 243 g (8.6 oz), making up 20.5% by number and 65.1% by biomass, although wood mice were the most numerous found prey in pellets. Because of the access to rats, the mean prey size in the north Italian study was an exceptionally high 58 g (2.0 oz) Generally, Mus mice seem to be the main foods for long-eared owls in Greece, especially the Macedonian mouse (Mus macedonicus), but also not infrequently the southern vole (Microtus levis) is important in the diet there as well. In the Canary Islands, the introduced house mouse (Mus musculus) was deemed to primarily support the owls today, consisting of 69.5% of 3,628 prey items per the largest known study.
Outside of Europe within Eurasia, the feeding association with voles for long-eared owls weakens somewhat but does continue apiece in adjacent Turkey, particularly southern vole and Günther's vole (Microtus guentheri) (the latter, for instance, making up to 78.7% of 5,324 prey items in Karapınar). In the Middle East, prey preferences varied based on soil composition in desert edge areas, with Israeli studies showing primary shifting rapidly from Gerbillus gerbil species to Meriones jirds to Günther's voles, with similar findings in wintering owls in Iran. Relatively large-sized prey, Indian gerbils (Tatera indica) and short-tailed bandicoot rats (Nesokia indica),  was reported for wintering long-eared owls in Iran estimated to average 163 g (5.7 oz) and 155 g (5.5 oz), respectively, constituted a good portion of the prey (72.9% of biomass) and taken in almost even numbers with smaller Gerbillus species. Much further east, in China and Mongolia, long-eared owls often subsist on different varieties rodent, especially small hamsters, which are also cricetid but not arvicoline, such as the Chinese striped (Cricetulus barabensis) and Roborovski dwarves (Phodopus roborovskii), alternatively with larger jirds, such as midday jirds (Meriones meridianus), as well as house mice. In more northerly eastern regions, voles continue to be of import. In western Siberia, tundra voles, narrow-headed voles (Microtus gregalis), Eurasian harvest mouse (Micromys minutus) and steppe lemming (Lagurus lagurus) were the main rodent prey. In Japan, diet is strongly biased to rodents such as Japanese grass vole (Microtus montebelli) (84.2% of foods in Niigata on Honshu), grey red-backed vole (Myodes rufocanus) (87.2% on Hokkaido) or house mouse (77.7% in Ehime Prefecture, Shikoku).
In North America, long-eared owls also primarily rely on small rodents in their diet, but their diet is somewhat more diverse by rodent family and less completely reliant on voles than their Eurasian counterparts. In general, the further north they are found in North America, the more restricted and vole based the diet is for this species. While diets are poorly researched in detail in Canada, in the northern tier states of Massachusetts, Michigan, Minnesota, Ohio, New York, Wisconsin and northern Oregon voles were easily the main prey for long-eared owls. In particular, the meadow vole (Microtus pennsylvanicus) tends to be a dietary staple, such as in the two of the larger American studies, in Michigan where they constituted 70.6% of 3,269 prey items and in Wisconsin where they constituted 83.4% of 3,273 prey items. Another regularly featured vole in the diet in America is the prairie vole (Microtus ochrogaster), but few other voles seem to be taken other than opportunistically excluding Oregon where the gray-tailed vole (Microtus canicaudus) and Townsend's vole (Microtus townsendii) locally led the foods. In North America, non-arvicoline cricetid rodents such as the genus Peromyscus, or deermice, and the smaller Reithrodontomys, or harvest mice, fill the niche of small wild mice and may be irresistible to hunting long-eared owls. Peromyscus mice were the main foods for this species in Colorado, Illinois and most studies from Iowa (composing up to 59.1% of the local diet).
In many areas, particular arid vicinities, the superfamily Geomyoidea supplants cricetid rodents as the primary foods, namely pocket mice, kangaroo rats and occasionally pocket gophers and jumping mice. Particularly this appears to be the case in the American southwest where in Arizona, Perognathus pocket mice composed 61.3% of the diet, in New Mexico, where species pairs of pocket mice and kangaroo rats composed 51.8% and 20.5% of the foods, respectively, and in southern California, where Perognathus were 51% of foods and Dipodomys kangaroo rats were a further 37.8% of the foods. In the Sonoran desert of Mexico, nearly all known prey were geomyoids, in particular the Merriam's kangaroo rat (Dipodomys merriami), which alone made up 74.7% of the foods. In a well-studied population, Snake River region of southeastern Idaho as well as Owyhee county in the southwest part of the state, geomyoid rodents are usually the most prominent prey, especially the Great Basin pocket mouse (Perognathus parvus) and Ord's kangaroo rat (Dipodomys ordii) (often supplemented heavily with Peromyscus mice). Due to the relatively large size of kangaroo rats, in Idaho, mean prey size may range up to at least 41 g (1.4 oz) In some parts of North America, richer biomass are likely when larger prey takes the primary position, such as cotton rats. Cotton rats were the main prey in Janos Biosphere Reserve, Mexico (43.2% by number, 69.1% by biomass) and in Texas, in the latter slightly outnumbering (36%) the much smaller harvest mice (23%). Since the mean body size of hispid cotton rats (Sigmodon hispidus) caught reportedly is around 100 g (3.5 oz), they probably represent a very productive prey resource for long-eared owls. Similarly, exceptional large prey was taken northeastern Oregon, where both juvenile, weighing about 30 g (1.1 oz) and adult, weighing about 90 g (3.2 oz), northern pocket gophers (Thomomys talpoides) were caught and made up 55.7% by number and 74.4% by biomass of the diets of long-eared owls. Depending on circumstances, the mean size of northern pocket gophers taken in different areas can vary from 41 to 100 g (1.4 to 3.5 oz) or higher, but long-eared owls usually take juveniles outside of the Oregon study (weighing on the lower end of that mass scale).
Non-rodent mammalian prey is seldom of great import to long-eared owls, though they can take some numbers of other kinds of mammals locally. Despite claims that the long-eared owls “avoids” shrews as prey, it is probably more correct to say that they do not seek them out nearly as often as more socially inclined and/or densely populated rodent prey. Some other owls may be considered regular and common shrew predators, such as often barn owls. In Europe, a broad picture of prey selection indicates about 2% of the diet of long-eared owls consists of shrews. Locally, relatively high numbers of shrews were reported in Finland, where 10.7% of 3,759 prey items were common shrews (Sorex araneus), in southern Scotland, where the common shrew made up 17.3% of 514 prey items, in northeast Greece, where lesser white-toothed shrew (Crocidura suaveolens)  were 19.3% of 311 prey items and in western Siberia, where Sorex species were 17.3% of 335 prey items. Similarly, in North America, shrews are rarely more than secondary prey. Exceptionally high numbers of shrews were noted in Ohio, where the relatively large northern short-tailed shrew (Blarina brevicauda) and the relatively small North American least shrew (Cryptotis parva) made up 10.46% and 10.22% of the diet, respectively, and in Tennessee, where 12.85% of the diet was least shrew. The smallest mammal on earth (and thus smallest recorded mammalian or vertebrate prey), the 1.8 g (0.063 oz) Etruscan shrew (Suncus etruscus), may be seldom hunted by long-eared owls. Bats are another supplemental prey type for long-eared owls. One compilation study based on 12 study sites in the Mediterranean area (in Spain, Italy, Greece, Slovenia, Romania and Switzerland) found up to 2% of prey remains were bats. The bats taken in the Mediterranean region ranged in size from the whiskered bat (Myotis mystacinus), estimated at as low as 4 g (0.14 oz), to the European free-tailed bat (Tadarida teniotis), estimated to weigh up to 54 g (1.9 oz). A exceptionally close predatory relationship was noted between bats, especially Japanese house bats (Pipistrellus abramus), and long-eared owls in the Beijing area of China, where bats accounted for 28.6% of 3,561 prey items overall, and 56.6% of the diet locally in urban, rather than suburban, roosts. Other mammals, outside of aforementioned groups (i.e. cricetid, murid and geomyoid) rodents, are known to be hunted but are generally a negligible part of the long-eared owl's diet, including hedgehogs, moles, rabbits and hares and weasels as well as rarely taken rodents like dormice, flying squirrels and squirrels (including chipmunks). While lagomorphs such as hares and rabbits are very rare prey for long-eared owls, occasionally they may capture one. Such prey was estimated to weigh 271 g (9.6 oz) (for cottontail rabbits) and 471 g (1.038 lb) (for jackrabbits) in Idaho, meaning very small young rabbits and jackrabbits are likely captured. However, sometimes long-eared owls can very rarely capture exceptionally large lagomorphs. The record sized mammalian prey to be taken by a long-eared owl, was recorded in the case of predation upon a probable juvenile black-tailed jackrabbit (Lepus californicus) which weighed an estimated 800 g (1.8 lb). Two instances of scavenging on carrion were reported in Italy, the first known case of this for the species, where long-eared owls consumed parts of an adult crested porcupine (Hystrix cristata) and an adult European pine marten (Martes martes), both prey the long-eared owls were certainly unlikely to have killed.


Long-eared owls are generally infrequent predators of birds. Food studies from Eurasia place it as an opportunistic and occasional bird predator, while in North America they are do not seem to generally take large numbers of birds in any area. In winter, sometimes these owls can come to live largely off of small birds gathered in communal sleeping places, often near villages or towns. Particularly snow cover during winter is likely to influence local long-eared owls to switch from mammalian to avian prey. Like barn owls, long-eared owls have been known to hover around roosts in bushes in attempts to disturb the sleeping birds, which may provoke the prey to fly out of their shelter, only to be caught. Long-eared owls, along with migrating short-eared owls, were observed in Spain hunting night-migrating passerines that were attracted to manmade light sources. When killing birds, long-eared owls are very likely to peck about the rear part of the body and the head and decapitate their victims, resulting in more skeletal damage than is typical in other owls and making prey identification potentially difficult. Particularly often taken by long-eared owls in urban areas and/or the edge of arid habitat are house sparrows (Passer domesticus) and occasionally the Eurasian tree sparrow (Passer montanus). A surprisingly high balance of prey for wintering long-eared owls in desert areas was shown to be avian. This was in the case in Algeria, where 37.5% of the diet and 40% of the biomass were avian and the most identified overall prey genus was Passer species, at 20.7% by number and 17% of biomass. For wintering owls in the city of Jerusalem, 90.7% of the diet (150 prey items) were small birds, led by house sparrow (22%) and the blackcap (Sylvia atricapilla) (16.7%). Further study of the long-eared owl's diet in Israel's Negev desert showed that 28.3% of 3,062 prey items were birds. In Egypt, 24.6% of prey items were birds including house sparrow (15.4%) and European goldfinch (Carduelis carduelis) (2.4%). In Europe, birds rarely compromise a majority of the foods, but hearty numbers are taken in several areas nonetheless. In central Europe, birds were estimated to contribute an average of 8% of the diet (of 52 species). In peak vole years, birds could be less than 2% of the foods while in vole low years, as much as 33% were made up of by birds. Similarly, in the Sofia park, Bulgaria, the number of birds, with an average 9.6% by number and 7.9% by biomass,  was variable based on vole numbers but a high number of 44 avian prey species were recorded. In the Sonian Forest, Belgium, 38.3% of 355 prey items were birds, mostly of various passerine species. A study in Baden-Württemberg, Germany found birds to compromise 14.75% of 12,890 prey items, a relatively high balance, with the most common identified bird species being the European goldfinch. Overall British studies found in a sample of 7,161 prey items that 1,161 were birds (14.95%) and that bird were present in 90% of examined pellets. Of these, 46.9% were house sparrow, 7.5% were common starling (Sturnus vulgaris), 4.65% were common blackbird (Turdus merula), 3.35% were European greenfinch (Chloris chloris), 2.92% were song thrush (Turdus philomelos), 2.49% were Eurasian skylark (Alauda arvensis) and 2.23% were common linnet (Linaria cannabina). More locally in the Peak District of England, birds were 23% of the prey by number and 31.3% by biomass. Of the birds examined here, a majority of those identified were meadow pipits (Anthus pratensis) followed by twite (Linaria flavirostris), and identified birds ranged in size from a probable wood warbler (Phylloscopus sibilatrix) (average adult weight 9.2 g (0.32 oz)) to an adult northern lapwing (Vanellus vanellus) (average adult weight 219 g (7.7 oz)). Furthermore, 80% by number and 11 of 25 bird prey species were characteristic of open habitat.
Many Italian studies reflect relatively high numbers of birds being hunted, mainly in the non-breeding times. One of the smaller large representations was at Prignano Cilento where 13.85% were made up of mostly unidentified birds. In Regional Park of Decima-Malafede, birds were 31.1% of the diet, 13.7% of which were unidentified passerines, while European goldfinches and European greenfinch accounted for a further 7.1% and 4.6% of the prey items. In the Venice area, of 642 prey items examined and a total prey mass of 15,038 g (33.153 lb), birds made up 38.47% by number and 41% of the biomass. In the winter roost of Imperia, 63.43% of 1,020 prey items were birds and 36.57% were mammals. The main prey identified was the blackcap (51.6%) while the chaffinch (Fringilla coelebs) was secondary among avian prey (6.73%). In Romanian studies avian prey was relatively important as well.  In Agigea there, 32.71% of the foods were birds, with Carduelis species combined constituting 6.04% and swallows being secondary such as the common house martin (Delichon urbicum) (2.52%) and the barn swallow (Hirundo rustica) (2.44%). Birds were the main foods for wintering long-eared owls in Romania's Danube delta, with birds making up 59.5% of total prey by number and 51.6% by biomass of 948 prey items against 40.7% by number and 48.4% by biomass for mammals. Here, numerous passerines were mostly taken with the finch family (18.6%), Old World sparrow family (15.7%) and the tit family (12.7%) being the commonest prey families among the birds. The mean bird prey size was calculated at 22.2 g (0.78 oz) while the mean mammal prey size was 24 g (0.85 oz). House sparrows accounted for 14.3% of biomass and Eurasian blackbirds for 12.3% of the biomass on the Danube. While mammals usually are dominant in the diets of long-eared owls in Spain, in the Albufera reserve of the nation, birds were 53.5% by number and 48.6% of the biomass of 864 prey items. A total of 34 species of birds were noted, led by common chiffchaff (Phylloscopus collybita) (12.5% by number, 4.8% by biomass), house sparrow (8.2% by number, 12.2% by biomass), barn swallow (6.4% by number, 7% by biomass) and sand martin (Riparia riparia) (3.2% by number, 2.7% by biomass). The main recorded individual prey species in Beijing was the Eurasian tree sparrow, at 38% of the diet, but other avian prey was negligible here.
While most of the passerines attacked by long-eared owls are well within typical prey sizes for this species, while pursuing bird prey many reports note that unusually large prey may be attacked. Avian prey weighing around 100 g (3.5 oz) or somewhat higher such as the larger common thrushes or jays is not uncommonly taken. However, unusually large bird prey for long-eared owls in Europe has included several species at least twice as massive, including adults of the following species: northern lapwings, common wood pigeon (Columbus palumbus), with an average adult weight of 490 g (1.08 lb), common moorhens (Gallinula chloropus), with an average adult weight of 343 g (12.1 oz), red-legged partridges (Alectoris rufa), with an average adult weight of 528 g (1.164 lb), western jackdaws (Corvus monedula), with an average adult weight of 246 g (8.7 oz) and Eurasian magpies (Pica pica), with an average adult weight of 230 g (8.1 oz). Much of the largest identifiable and provable prey for long-eared owls in Europe overall were found to be birds. Despite the relatively scarcity of avian prey in the diet in North America, unusually large avian prey has been reported there as well. Such prey have included adults of Northwestern crow (Corvus caurinus), averaging 392 g (13.8 oz), two large adult ruffed grouse (Bonasa umbellus), estimated to weigh slightly over 600 g (1.3 lb), and even apparently at least once an adult sharp-tailed grouse (Tympanuchus phasianellus), which average a relatively huge 885 g (1.951 lb) or three times heavier than an average long-eared owl.


Other than mammals, which compromise a great majority of foods, and birds, which compromise a secondary but locally important portion of the foods, other prey varieties are seldom taken by long-eared owls anywhere. Infrequently, reptiles such as handful of species of snakes and lizards and even fewer amphibians such as frogs and toads. Generally these prey turn up more than singly only as far as is known in slightly arid warmer parts of the species range, mostly within the Canary islands and occasionally the American southwest. Fish are almost never recorded in the diet with a total of two prey fish species, both carp and further unidentified carp, recorded in Europe. Despite a rather high diversities of insects (and a low diversity of other invertebrates like arachnids) collected overall, especially in different parts of Eurasia, they are rarely significant contributors to the long-eared owl's diet. Usually in Europe, if any insects are found in pellets, they tend to contribute less than 2% to the prey numbers. Similarly present but slight numbers of insects were noted in Israel as well. Exceptionally large contributor of insects, most often a variety of species or genera of beetle, to prey numbers are noted in some studies such as contributing 6.6% of the diet in Regional Park of Decima-Malafede in Italy, 17.5% in northeastern Greece and 13.3% in western Spain. The record contribution for insects surely for Europe was study in central Poland where a single beetle, the common cockchafer (Melolontha melolontha), was found to constitute 25% of the prey items. Based on a couple studies in Algeria, insects are a common supplemental food there, contributing up to about 17.3% of the prey items. On the isle of Tenerife in the Canary islands, an exceptional 33% of the food was recorded to be insects, with both bush crickets and field crickets contributing 14.8% each, although in broader Canary island studies the significance of insects is reduced to 10.4%. The maximum known contribution of insects to the diet in North America was merely 4.3% of the foods for communal roosting long-eared owls in southeast Idaho.


The long-eared owl occurs in multiple competitive environments of the temperate zone alongside other birds of prey. A wide variety of owls are especially likely to be encountered both in terms of shared nocturnality and a shared preference for rodent prey, which is favored by about 75% of owls found in North America and about 85% of the owls found in Europe and occasionally favored by nearly all owls in both continents. Much study has gone into contrasting the ecology of long-eared owls against other owls and also occasionally diurnal birds of prey, especially in terms of differences in dietary habits and habitat preferences. In Europe, arguably the most populous owl is likely the tawny owl, which has therefore warranted a considerable number of comparisons with long-eared owls. While tawny owls overlap in prey preferences with the long-eared owl, it tends to show greater dietary flexibility, with larger contributions of secondary prey such as birds, reptiles and amphibians and insects. For example, in southern Sweden, the food niche breadth of tawny owls was roughly three times greater than that of long-eared owls. Generally tawny owls prefer more extensively wooded environments than long-eared owls but can adapt as well as the long-eared to forest fragmentation and peri-urbanisation, thus often competing rather directly over foods. While the tawny owl usually selects slightly larger prey on average than long-eared owls, often over 30 g (1.1 oz) mean prey mass, studied size of common voles hunted in central Lithuania showed that both long-eared and tawny owls selected larger than average voles, with average caught estimated at 21.45 g (0.757 oz) against the average weight surveyed by humans at 16.42 g (0.579 oz). Surprisingly, especially in the non-breeding season in this study, long-eared owls in Lithuania tended to select larger voles on average (at 21.56 g (0.761 oz)) than did tawny owls (19.56 g (0.690 oz)). Despite the potential for competition and mortality (for long-eared owls) in the interspecific relationship between the tawny and long-eared owls, the proximity of tawny owls in a study from Switzerland appeared to have no deleterious effect on the breeding on the long-eared species. A few studies have examined the habits of the little owl, probably the next most common European owl and just ahead of the long-eared owl in third, and the long-eared owl in areas where their somewhat overlapping habitat preferences draw them into similar areas. However, the long-eared owl takes larger prey on average usually than little owls, since it focuses more on rodents rather than invertebrates like insects and earthworms and, especially during winter, varies its prey compositions less so than the smaller species. Also, the long-eared owl requires some timbered spots for roosting purposes while little owls can adapt to both treeless and partially treed areas as well as, in Spain at least, more heavily modified areas by humans. Many diurnal raptors in Europe broadly overlap in dietary habits, largely taking voles where they are available, including most species of harrier, buzzards and some falcons, especially common kestrels (Falco tinnunculus). Other than occasional predatory interactions, competition is limited with most of these diurnal birds of prey due to the temporal differences of their habits. In Europe, several other owls, from ones much smaller than to a few species much larger than a long-eared owl, prefer voles and/or lemmings as prey but often differ considerably in their habitat preferences, distributions, nesting habits and/or hunting habits so the long-eared owls are largely naturally partitioned from competing directly with them.
On a broader scale, both short-eared owls and barn owls potentially compete for resources with long-eared owls. Despite considerable overlap in both range and diet, long-eared owls are largely buffered from considerable competition with short-eared owls by habitat preferences, as the short-eared owls always venture to more open habitats, generally roosting and nesting in tall grasses rather than timber, and seldom, if ever, hunt in the same edge habitats as the long-eared species. In western Russia when compared to short-eared owl, long-eared owl showed less of a tendency to appear in cluster where prey was concentrated, most likely because of the habitat differences. In both western Russia and further east in western Siberia, the short-eared tended to take more tundra voles in addition to common voles, while long-eared owls focused more exclusively on common voles. Comparisons between barn and long-eared owls have been made in many areas of the latter species less extensive range. The habitats used by the barn and long-eared owls are not mutually exclusive nor are their prey species. Despite being similar aerial hunters of open areas, barn owls differ in life history in many respects from long-eared owls, in part by being cavity nesters. While their dietary habits can appear similar and show similar dependence on small mammals, barn owls are somewhat more generalized and catholic as feeders, with less of a heavy reliance on voles. Barn owls can live quite well on virtually any small mammal assemblage. In some parts of Europe, the two species’ food niche breadth is comparable or even slightly higher in the long-eared. However, globally barn owls are much more wide-ranging, more tropical in their central range and globally have a much wider prey spectrum than long-eared owls. Barn owls are also more widely adaptive to insular living than long-eared owls, and are capable living proficiently on a diversity of prey classes even in environments completely lacking small mammals. The American barn owl race is larger than the western barn owl race from Europe and relevant parts of Asia, being more comparable in body mass and foot and talon size to the tawny owl while the western race in Europe is roughly intermediate between the tawny and long-eared owls in body size and foot span. Consequently, in the Americas, barn owls tend to consistently take slightly larger prey than long-eared owls and tend to access a broader overall feeding niche. Despite the great adaptability and range of the barn owl, it was found in a study from France that they experience higher mortality due to starvation than long-eared and tawny owls. This was attributed to the barn owl's inferior lipid fat reserves while they attempt to survive the cooler seasons within temperate climates, as they are better suited to survival in warmer climates.
North America has more species of owl than Europe and can be considered a more competitive environment for long-eared owls living there. However, again, in most cases habitat preferences, slight partitioning in dietary preferences (which may be in prey species or body sizes of prey selected) and life histories generally allow most species to persist even when living in proximity to one another. As throughout their range, long-eared owls tend to differ from most other North American owls by being much more migratory in nature. Therefore, cyclic food variations affect them differently and are less likely to be the direct cause of winter mortality than in more permanently residential owls. Oddly enough, among American owls, long-eared owls most strongly mirror the much smaller northern saw-whet owl in distribution, migratory habits and, to a lesser extent, food habits. The main food of saw-whet owls tends to be Peromyscus mice where they are available and, like most owls, their rodent food selection can broadly overlap with that of long-eared owls. It has been posited that the less broadly ranging occurrence of long-eared owls in general compared to in their European range is in part due to greater resource competition between them and the two widespread screech owls, the eastern (Megascops asio) and western screech owls (Megascops kennicotti). However, the feeding niche tends to be much wider and more opportunistic in screech owls, which often feed on a diversity of invertebrates (mainly insects but also crayfish) and alternate prey (a higher balance of birds and frogs, for instance) and so are unlikely to competitively limit rodent numbers to the detriment of long-eared owls.
The most easily observed and most dramatic portion of interspecies owl and raptor ecology is interspecific predations. In this regard, long-eared owls are much more often the victims rather than the predators. Their generally successful life history on the contrary often makes long-eared owls perhaps more vulnerable than most other medium-sized owls to predations and even perhaps many smaller owl species. These include nesting in relatively open abandoned bird nests rather than hard to access cavities. Also, long-eared owls tendency to occur in quite open areas whilst hunting coupled with the loud vocalizations (including begging calls of their fledglings) and other auditory displays are all likely to court predators. In Europe, their most serious predators tend to be the Eurasian eagle-owl and the northern goshawk (Accipiter gentilis). One account recorded 768 instances of predation by eagle-owls and 317 by goshawks (or 55% of the owl prey for recorded for goshawks in Europe). Long-eared owls rank in the five most regular predated bird species by eagle-owls in Europe. Some biologists feel that long-eared owls tendency to avoid richer prey concentrations in favor of opener habitats and spatial usage, especially while migrating and wintering, is partial dictated by the detection of eagle-owl (and perhaps goshawk) activity, so therefore the eagle-owl has a serious influence on the long-eared owl's life history. In general, long-eared owls endure predation by a formidable array of diurnal birds of prey in Europe. It is likely that largely perch hunting raptor such as Buteo and most eagles may either chance upon an owl roost during a hunting foray or encounter a long-eared owl perhaps during overlapping activity around dawn or dusk, while large falcons are likely to only strike one down when an owl is flushed during daytime. Goshawks and other Accipiter hawks are a particularly deadly threat among diurnal raptors due to their intensive searching hunting methods and willingness to dive into wooded thickets holding roosting owls. Beyond goshawks, diurnal raptors in Europe known to be predators of long-eared owls of potentially any age are known to include golden eagle (Aquila chrysaetos), Bonelli's eagle (Aquila fasciata), eastern imperial eagle (Aquila heliaca), greater spotted eagle (Clanga clanga), lesser spotted eagle (Clanga pomarina), black kite (Milvus migrans), red kite (Milvus milvus), white-tailed eagle (Haliaeetus albicilla), common buzzard, rough-legged buzzard (Buteo lagopus), peregrine falcon (Falco peregrinus), saker falcon (Falco cherrug) and even (in two cases) the slightly smaller Eurasian sparrowhawk (Accipiter nisus). Other than eagle-owls, tawny owls and Ural owls (Strix uralensis) regularly kill long-eared owls where their ranges meet, though in some cases these may begin as territorial attacks by the Strix owls, the smaller long-eared may be consumed regardless.
In North America, the range of predators of long-eared owls is no less daunting. Undoubtedly the most dangerous American predator is the great horned owl. Similarly as in its European eagle-owl counterpart, horned owls kill long-eared owls regardless of season and conditions. However, despite many accounts of predation, long-eared owls do not generally seem to be as prominent in the diet of great horned owls, at least as so far documented, as they are in the diet of Eurasian eagle-owls. Barred owls can also be somewhat serious predators of long-eared owls as well. Rarer acts of predation on long-eared owls in North America have reportedly been committed by spotted owls (Strix occidentalis) and even their cousins, the short-eared owl. Diurnal predators of long-eared owls including some species that also hunt them in Europe such as golden eagles, northern goshawks and peregrine falcons, as well as bald eagle (Haliaeetus leucocephalus), Cooper's hawk (Accipiter cooperii), red-tailed hawk (Buteo jamaicensis) and red-shouldered hawk (Buteo lineatus). Though less well documented throughout the range, long-eared owls are also vulnerable to mammalian predators, mainly near the nest. Suspected or confirmed predators in Europe are often European pine martens or stone martens (Martes foina), which are likely to depredate nestlings but also will consume eggs and adults if they are able to ambush them. Martens are also a potential threat in North America, as are the North American porcupine (Erethizon dorsatum), bullsnake (Pituophis catenifer) and, especially, the raccoon (Procyon lotor) (the latter species may semi-regularly kill and eat brooding adult female long-eared owls). Corvids, many of which build the nests long-eared owls use, such as magpies and crows will also semi-regularly raid the long-eared owl's nests and eat the eggs or nestlings. On the other side of the equation, long-eared owls themselves may infrequently prey on smaller owls. This species has been known to hunt eastern screech owls, little owls, Eurasian pygmy owls (Glaucidium passerinum) and boreal owls (Aegolius funereus), as well as the young of the common kestrel.


Long-eared owls tend to be monogamous breeders. Non-migratory populations are usually monogamous throughout the year, the pair bond being renewed annually. A study in Idaho determined that long-eared owls were locally extremely monogamous, with no extra-pair fertilizations were detected in 59 nestlings from 12 nests. There is a single record of a male breeding with 2 females in Netherlands, a very atypical case. Similarly, evidence of polyandry and alloparenting was found in a nest in western Montana where the four offspring of the female owl had two fathers, one of which was related to the female. Males claim their territory with singing and display flights with wing clapping. Singing normally starts at dusk on calm evenings and may continue through the night, clear windless moonlit nights are preferred. The song is usually delivered from a perch, most often at medium height in trees or from the upper half near the canopy, sometimes in flight. Males are responsive to playback during the period leading up to the breeding season (especially during courtship), to such a degree 45% territories would've been undetected in Spain if males has not responded to recordings (as opposed to listening for spontaneous callings). Often between 8 and 50 pairs are recorded in different parts of the range in a typical range of 100 km² (39 sq mi). In Scotland, about 17% of the 9-18 pairs per 10 km² (3.9 sq mi) were non-breeders. Typical territories for pairs are 50 to 100 ha (0.19 to 0.39 sq mi) in Finland when voles are plentiful. Several pairs may nest rather close together nonetheless. The minimal distance is normally around 50 to 150 m (160 to 490 ft) between active nests, but in Idaho a nearest nest distance of only 16 m (52 ft) was recorded. When food is abundant, about 10-12 pairs, infrequently as many as 50, may nest within area of 100 km² (39 sq mi). Pairs may tolerate each other in the same patch of trees while nesting if food supplies are abundant. A study in Province of Pisa of Italy of 32 territories found 10-15 pairs per 100 km² (39 sq mi) with a mean nest spacing of 1,727 m (5,666 ft). In a south-central Idaho study area, pair occurred on average 0.65 km (0.40 mi) apart. The highest densities may come from central Europe. The average density in central Europe is typically around 10-12 pairs per 100 km² (39 sq mi). However, in Brandenburg, Germany, over a 24-year study, it was found the average density was 72.7 pairs per 100 km² (39 sq mi). Based on studies from Michigan and Wyoming, anywhere from 10 to 100 pairs per 100 km² (39 sq mi) was estimated, with the average range in Wyoming riparian habitat about 55 ha (0.21 sq mi). Densities appeared lower in the Snake River area (0.28-0.42 pairs per square km) than elsewhere in southern Idaho (0.64-1.55 pairs per square km). Globally, many pairs of long-eared owl occupy the same territory all year around but most prefer to use a different nest each year even if the same nest as last year is still in good standing. Females typically take on the duty of inspecting potential nesting sites and duets with its mate; perched on a chosen nest, she sings to contact the male, later vocal activity is confined to weak calls only heard at short range. During displays, females have also have been recorded doing the wing clap display but much less intensely than males. Copulation tends to occur close to the nest. In Germany, it was recorded that the male precedes copulation with calls and display flights, followed by strong waving wing signals and tilting their body while perched near female and/or the nest. Copulation has also been observed on both the ground and the trees, preceded frequently by a duet, a male aerial display which ending in descent to ground and a flight by the female. Boundary fights between males are unrecorded in this species. Breeding occurs later in the year than sympatric species such as tawny owls and barn owls perhaps due to their more strongly migratory ways. Rarely mating may occur early as February in cooler temperate areas, but the pairs copulations usually take place in March or April. Winter breeding detected as new juveniles of 14–18 days of age were recorded in early February in Slovakia. Other prior reports of winter breeding are known from Italy, in two cases, as well as in the Czech Republic.
Normally nests in stick nest of large birds, i.e. Corvus, Pica, raptors and Ardea herons. Other nest builders in Europe can often include common wood pigeons and Eurasian sparrowhawks. In Britain and Finland 84% of 239 and 85 nest were made by carrion (Corvus corone) or hooded crows (Corvus cornix) and Eurasian magpies. In England and Finland, 77% and 66% of the nest were in conifers, respectively. In Brandenburg, Germany, 90% of the nest were built by carrion crows and most were in Pinus sylvestris. In different studies of Idaho, nearly all known nests were in old corvid nests (most being in juniper). In one large study, nest heights, which averaged 3.2 m (10 ft), and diameter of the nest construction, which averaged 22.3 cm (8.8 in), were deemed likely to be the most significant criteria for nest selection. In Ontario, conifers were usually used, often Pinus or Juniperus, in corvid nests between 2.5 and 18.5 m (8.2 and 60.7 ft) high, but mostly between 5.5 and 9 m (18 and 30 ft). Nest height averaged 6.7 m (22 ft) in Great Britain. In Slovenia, long-eared owls preferred coniferous trees for breeding (in almost exclusively corvid nests), those that nested in deciduous trees had higher nest mortality especially earlier in the season due to higher predation rates. Similarly, nest site selection was largely correlated to predation risk in Spain, with ivy and tree canopy coverage less important than high scrub cover from below, in part because terrestrial predators were more common in the particular study area than aerial ones. In northeast Switzerland, nesting location are selected for anti-predator features, among 38 nesting sites, the ones seemingly preferred bore denser forest edges, greater canopy cover and were within conifers much more so than were prevalent in the overall environment, while the vicinities of buildings were avoided in the study area. An unusual case of urban breeding long-eared owls was observed in Moscow, Russia, where a loose colony was observed to form. The Moscow nesting was thought to be the result of synanthropization by the owls, in part due to lower predation risk in the urban areas versus rural vicinities (where predation was 6.6% higher). The mean distance of nesting owls in Moscow was 603 m (1,978 ft) whereas it was more than twice the distance in nearby rural areas. Tree nests are usually under 30 m (98 ft) above the ground, and can sometimes be so small that the wings and tail of brooding female may be visible from below. More infrequently than avian tree nests, leaf nests of tree squirrels, hawk nests in cacti and cliff nests of various birds may be used. While they usually take up already abandoned nest sites, sometimes long-eared owls are capable of chasing off prior occupant of nest even including other raptors (extending to fierce Accipiters such as sparrowhawks, sharp-shinned hawks and even larger Cooper's hawks) indicative of their potential for fierceness and tenacity. Other than other bird's nests, alternate nesting sites have been used but appear to be usually rare or uncommon. Among these, are shallow depressions on the ground. Some ground nest locations recorded (in Europe) have included among heather, bracken and bramble, and even on reed beds, rabbit warrens. Some nests have been recorded in wicker baskets placed in trees for ducks. In North America, pairs of ground nest were found in each west-central Montana and in Okavagan, British Columbia, in all cases between the roots of or the ground immediate adjacent to the base of trees or bushes (with two other historic records of ground nesting in North America). Artificial nesting platforms made of twigs for the owls are also locally accepted. In Woodwalton Fen reserve of eastern England, 71 nests were built in wicker baskets set out for owls. Also in Yizre'el in Israel, 6 of 16 nest baskets hung in Eucalyptus were used by long-eared owls, with all occupied by February. In this general area of Israel, at least 72 other nest baskets for long-eared owls have been set out, to encourage the rodent controlling birds.  Exceptionally, long-eared owls have nested in shallow cavities, in hollow willows or oaks, tree stumps or holes in cliffsides, however as a rule they tend to not be cavity nesters. 6.5% of 153 nests in Great Britain were on natural surfaces (mostly the ground) rather than animal nests. Nesting vicinities where previous attempts were successful are more likely to be reused, i.e. in Idaho where 48% of prior nesting areas were reused after successful attempts.
Egg-laying is between normally between late March and early May in most of the range. Egg laying dates in the northeastern United States, in a sample of 42 eggs, were between March 14 and May 30. Additional records in southern Canada show laying as occurring at as late as June 5. 43 eggs in Ontario were laid between March 19 to May 24, more than half between April 15 and May 5. In northern Italy, the mean egg laying date was March 27. Exceptional eggs were recorded as early as December 31 to January 3 in Spain. Re-nesting can occur within about 20 days after a clutch is lost. In Europe up to two broods have been successfully been raised at times of food abundance. Generally the female lays 3-5 eggs (sometimes more if food is unusually abundant).  Larger clutches are typical further north in the range. Record sized clutches have been recorded for Europe of up to 8 eggs in Sweden in years of a “vole plague” while record sized clutches worldwide were recorded of 10–11 in the Kazan area of Russia in similar conditions. In Great Britain, the average clutch size was recorded as 3.9 while in Germany it was 5.5 and, similarly, in Slovenia it was 5.6. In a study from Montana, the mean clutch size was 5. The pure white eggs are 40.2 mm × 32.5 mm (1.58 in × 1.28 in) on average in both North America and central Europe and weight about 23 g (0.81 oz). At 1-5 day intervals (on average 2), the eggs are laid on the bottom of nesting area. A clutch of 7 eggs takes 10 to 11 days to lay. Incubation begins with the first egg and continues for about 27–28 days (in extreme cases from about 21 to 30 days). The female alone incubates while the male provides food, which is brought direct to nest. She may leave the nest early on to feed but does so much less later into incubation. A study in Montana found that corticosterone levels were considerably higher in adults of both sexes during the breeding season than during the non-breeding season, suggesting that the breeding season is more stressful on the owls.
The young hatch at 2 day intervals at any point between very late April and June. The average weight of 52 hatchlings in Montana was 18.4 g (0.65 oz). Their eyes open at 5–7 days (averaging 6.4 days in Montana) and they are brooded by the mother for about 2 weeks, often while the male perches nearby and watches over. The female alone feeds the chicks. In Idaho, the male was recorded to 2.5 times more prey deliveries during nesting than did the female. Injury feigning displays have been recorded at the nestling stage as an anti-predation measure. Usually long-eared owls are less bold in nest defense than some other owls, Strix owls for example, but they are capable of fierce protective attack nonetheless. Nesting defense by parents increased in Italy further into breeding season, with older nestlings being defended more vigorously. Females do a majority of nest defenses. Owl pairs incurring higher levels of regular disturbance are more likely to have a milder nest defense. During a defensive display, the parent ruffles up their plumage and partially spreads the wings to half open, trampling from one foot to the other, hissing and bill snapping and can look surprisingly large in this posture. If a perceived threat continues towards the owls, they may leap up and try to rake and grab at the threat with their talons. Even animals as large as humans may find themselves the victim of long-eared owl defensive attacks if they approach or, especially, if they climb up to a nest. The young leave the nest at 20–27 days of age (average about 22 days) but are initially flightless, often climbing about surrounding branches. At this stage they may be referred to as "branchers". Quite often the young fall to the ground, but they are usually able to climb back up using their claws and bill with heavy wing flapping. At dusk the begging branchers call to their parents with high pitched notes to indicate their location. At about 35–37 days, they are fully fledged and can fly well, but they often follow their parents and are fed by them for up to about 2 months, continuing to make high pitched calls. In Slovenia, independence was gained about 50–80 days after hatching, while in Idaho it was about 45 to 56 days.
Normally in North  America the species produces one clutch per year, but 2 clutches in a year have been recorded in high vole years. An exceptional double brood was recorded in Idaho due to high food availability, allowing the pair to successfully raise all 11 nestlings to fledgling, while in same season 3 other females in same grove were able to produce an average of 5.3 fledglings in their single broods. Like other species using open nests, rather than enclosed cavities, the species has relatively short fledging period and quickly moves away from the dangerous situation of the nest site. Nesting success averaged 46% between two study years in a study of 112 nests in Idaho with raccoon predation considered the most serious cause of nesting failure. A different Idaho study of 24 nests showed that the owls fledged an average of 3.7 young per nest. In Montana, the mean number hatched per nest was 3.8 and mean number to have fledged per nest was approximately 2.2. 59% of 78 nesting attempts failed in Britain, with an average clutch size per successful pair of 3.91 to 4.53. 41 of 78 continuously monitored in this British study nest successfully produced 1 or more fledglings.  In another British study, of 58 monitored pairs over 4 years, 83% laid eggs, 63% hatched one or more young, and 57% fledged young, with an average of 3.2 young fledged per successful nest. In yet another English study, this time exclusively of owls using wicker baskets, 50.7% of 71 attempts managed to fledge young. Among the wicker basket users, earlier nesters (i.e. March-early April) raised larger broods and had more fledglings than later (late April-early May), in part due to rising water tables making prey capture less ideal later in nesting season. For 6 pairs of long-eared owls using wicker baskets in Israel, the mean brood size was 3.6 and mean number of young owls to leave the nest was 3. At all stages and in all regions, reproduction tends to be more successful when prey populations are higher. In continental Europe, conditions are better than in England or Finland, perhaps due to the large population of common voles there that are absent in the more northerly countries, and nesting success averages higher. However, breeding success still is reliant on prey populations. In an 15 km² (5.8 sq mi) area of southern Germany, one cold spring with few voles no breeding pairs were found. A year later, with a warm spring and many voles, 19 breeding pairs took up residence in the study area. First year mortality of long-eared owls has been calculated in Germany as 52% and 31%. In Brandenburg, Germany, of 867 breeding attempts, 36.6% (335) pairs were successful in raising 1,468 young, which equates to 1.57 fledgling per all pairs that attempted, 4.31 per successful pair. The Brandenburg data shows that after 1990, when conservation minded farming initiative began, numbers increased significantly. Also in Brandenburg, in one case, 2 successive females to the same male were killed, the male mate was able to pair with a third female and resulting in a late successful fledging (August 24). In Slovenia, as studied between 1984 and 1993, of 79 nests, 32 (40%) produced young, 37 (47%) failed completely, and 10 (12%) failed after hatching. The Slovenian average number of owls hatched was 2.4 per nest (5.3 per successful nest) and the average number of owls fledged was 1.6 per nest (3.9 per successful nest). In Pisa, Italy, long-eared owl pairs produced a mean of 0.95 per territorial pair and 2.13 per successful pair. In central Slovenia, 57 nests produced an average of 5.7 eggs per clutch. Of the 51 fledged owls, 31 died in the study, 22 of which were due to mammal and bird predation, 6 due to starvation, 2 due to road collisions and 1 drowned in ditch. In Britain, the most common diagnosed cause of nest failure was egg theft by humans (accounting for 28.2% of 46 failed nests). Banding studies show that the long-eared owl typically have a short lifespan, with more than 91% of 105 owls recovered in North America of determined age being 4 years or younger. The oldest recorded in these efforts was banded in New York and recovered in Ontario at the age of 11 years and 4 months. Another one may have been over 15 years old, however. One exceptional isolated record is known of a European long-eared owl of just under 28 years of age. Annual survivorship in Germany and Switzerland for adults is 69%.


The long-eared owl is rather common and widespread in many regions. With a range of 80 million square kilometers, it is easily one of the most widely found owls. The IUCN estimates the total population between 2 million and 5.5 million, placing it as one of the most numerous owls beyond the wider ranging barn owl and less wide-ranging little owl (both likely between 5 and 10 million total birds) and roughly equaling the total population of great horned owls. The long-eared owl is more numerous than its more scarce but more wide-ranging cousin, the short-eared owl, with the peak number possible of short-ears roughly equivalent to the minimum number of long-ears. Their range of limit for breeding is typically in Mediterranean type arid, hot climates, where terrestrial insects and reptiles may prevail over small, sociable rodents, the long-eared owl is cut-off, whereas these are peak areas for barn owls. In the north, it is scarce to absent in areas of the deep boreal forest and the treeless northern areas such as around large wetland bogs or lower tundra, where the short-eared owl tends to supplant them. Densities of populations depend on availability of food. Local threats are typically pesticides and persecution. Out of myth and ignorance, this species has long been persecuted by humans. In many areas, some humans may carelessly shoot at any crow-like nest in order to destroy the contents, out of resentment for the crow's perception as a pest. In North America, hunters historically often shot long-eared owls as all owls were badly persecuted. Even though it was perceived early in the 20th century that the species is actually beneficial to human interests, many hunters continued to shoot them, claiming that they represent young individuals of the then nationally despised great horned owl. Largely in correlation with persecution, long-eared owls were recorded as formerly abundant and then rare in North America in the early 20th century. Long-eared owl potentially face lethal contamination with heavy metals such as mercury, organic biocides, including insecticides, fungicides and rodenticides and PCBs recorded. Pesticides seem to effect the species less than those predators with more varied diets and those that eat carrion. High levels of contamination were found in long-eared owl pellets in Serbia, with the concentrations of pollutants in prey that are sourced from industrial and agricultural practices in the region. Like many birds, they may be vulnerable to helminths, which are probably underrated as a potential source of mortality. Other parasites and mites may reduce health of populations. West Nile virus and Salmonella has been the recorded source of mortality for some long-eared owls. Anticoagulants may also threaten this species. In the Canary islands, it has become increasingly scarce due to loss of habitat. Many long-eared owls are also killed by road traffic. High owl mortality were particularly noted along roadways in France, especially due to high common vole numerous in roadside areas, proposed that letting vegetation grow may mitigate some mortalities. During 1963–1995, 128 dead long-eared owls turned in England, 89 were females and 34 were males. 61% turned had died from collisions (40% from those with vehicles). In this study from England, high levels of DDE (metabolite of DDT) and HEOD found in long-eared owls prior to 1977, similar levels to those seen in falcons there, lessened in later samples but 2 birds still had fatal levels of pesticide contamination. In areas such as Switzerland, to offset persecution and increase survival as well as to allow observers to watch them more easily, wintering owls in towns and cities were fed daily white lab mice. Breeding can be promoted by artificial platforms of twigs in bushes or trees. Also augmented feeding may ensure survival during low food winters. An attempt to release captive raised long-eared owl in the wild in Italy was largely unsuccessful. Of these, 3 of 8 attempted owls seemed to disperse successfully while the others died or disappeared, while 8 tawny owls released all but 1 seemed to successfully disperse. The species has actually increased in Iran, rising from 25 records over 12 decades to 49 records in two decades (between late 70s and 1997). Now breeding confirmed in up to 12 regions for the Persian breeding population and between 1997-2014 there were 32 non-breeding and 17 breeding records.
In southern California (San Diego county and Orange county), long-eared owls are thought to have lost more than 55% of their range due to habitat alterations. A decreasing trend has been observed in wintering owls in New Jersey, with 9 of 58 known roosts entirely eliminated due to land development, while the remaining 49 have shown reductions or are no longer used over the course of 30 years. Land use changes and habitat destruction accounts for reduced habitat quality and lower vole populations, with more adaptable raptors such as great horned owls and hawks exploiting much of what remains to the detriment of long-eared owls. A similar reduction was noted over 20 years in Pennsylvania. Broader studies of banding across Canada, gathered during long term monitoring from consistent annual bird counts from 1966–1992, showed that long-eared owl has declined relatively significantly. A net total 0.98% decline was recorded over the survey time. This was considered the second greatest reduction behind short-eared owl and burrowing owl (Athene cunicularia), furthermore among the 19 raptors surveyed in Canada, these 3 owls showed the most declining trends. The long-eared owl was apparently the most scarce of the 6 sub-boreal owl species surveyed. A similar trend has been detected throughout North America with a very large net 1.6% reduction overall during Christmas Bird Counts (CBC), again making it the most severe decline for an owl behind only the short-eared owl and the two related owl species seemed to have had the most severe declines of all 28 raptor species mentioned in these CBC surveys.


John James Audubon illustrates the "Long-eared Owl - Strix otus" as Plate 383 in Birds of America, published London, 1827–38. The print was engraved by Robert Havell in 1837. The original watercolour was purchased from Audubon's destitute widow by The New York History Society where it remained until 9/11, when it was destroyed.


Asparagus acutifolius, common name wild asparagus, is an evergreen perennial plant belonging to the genus Asparagus. The specific epithet, acutifolius, meaning "thorny leaves", is derived from Latin acutus (pointed, acute), and -folius (-leaved), and refers to the characteristic shape of the leaves, a quite common feature in the typical plants of the Mediterranean.


Asparagus acutifolius reaches on average 30–70 centimetres (12–28 in) of height. The stems have much-branched feathery foliage. The "leaves" are in fact needle-like modified stems. The flowers are bell-shaped and in small clusters, greenish-white to yellowish, 4.5–5.5 millimetres (0.18–0.22 in) long. The flowers are dioecious (on each plant they are only male or female). In some Mediterranean regions flowering occurs in late Summer from August through September, often after heavy storms. In this case the small green berries, of 5–6 millimetres (0.20–0.24 in) in diameter, are fully ripe in winter.


This species is present throughout the Mediterranean Basin.


These plants grow near woods and in uncultivated places, on dry and sunny soil. They can be found at an altitude of 0–1,300 metres (0–4,265 ft) above sea level.


This species reaches about  15 millimetres (0.59 in)  in length. Larvae have a gregarious habit and feed on Ipomoea species, with potentially dangerous impact on crops.


Aspidimorpha miliaris occurs throughout SE Asia and India.


The Chihuahuan spotted whiptail (Aspidoscelis exsanguis) is a species of lizard native to the United States in southern Arizona, southern New Mexico and southwestern Texas, and northern Mexico in northern Chihuahua and northern Sonora.
The species is believed to be the result of extensive hybridization between the little striped whiptail, Aspidoscelis inornatus, the plateau spotted whiptail, Aspidoscelis septemvittatus, and the western Mexico whiptail, Aspidoscelis costatus. It is one of many lizard species known to be parthenogenetic.


The Chihuahuan spotted whiptail grows from 9.5 to 12 inches in length. It is typically a reddish-brown in color, with six lighter colored stripes that run the length of the body, with spotting between the stripes. The underside is white or sometimes pale blue. It is slender-bodied with a tail nearly three times its body length.


The Sonoran spotted whiptail (Aspidoscelis sonorae) is a parthenogenic species of teiid lizard found in Arizona and New Mexico in the United States, and Mexico.


It is characterised by a short rhizome which gives rise to several green fronds that have a pinnated lamina with trichomes on the abaxial (lower) surface, but not the adaxial (upper) one. These trichomes (hairs) are orange-brown in colour, hence the name "rustyback". The petiole is shorter than the corpus of the leaf.


This species is found in Western and Central Europe, including the Mediterranean region, in the Arabian Peninsula and in temperate Asia as far east as Tibet. It is associated with fissures in carbonate rocks and also grows on the mortar of stone and brick walls. Can be found growing up to 2700 metres above the sea level, although it prefers mountainous locations, where it is usually found growing in sunny rocky walls and slopes.
Unlike many others, this fern likes growing in full sun, and requires little, if any, humidity.


It has been widely used for making infusions as a diuretic.


This fern is well known as a resurrection plant due to its ability to withstand desiccation and subsequently recover on rewetting. It has been shown that this is in part due to its high concentrations of phenolic compounds such as chlorogenic acid and caffeic acid which allow it to negate the destructive capacity of the reactive oxygen species generated by the drying process; the concentrations of these phenols decrease during the dehydration process. Enzymes such as peroxidase and polyphenol oxidase have also been shown to be important in allowing this fern to cope with desiccation; the concentrations of these enzymes increase when the fern is subjected to water shortages.


Asplenium flabellifolium is commonly known as the necklace fern. This small fern occurs in all states of Australia, as well as in New Zealand. It was initially described by Spanish botanist Antonio José Cavanilles.
Its natural habitats are open forest or rainforest. Usually on the ground, but sometimes epiphytic. Often seen in rock crevices, caves, on fallen logs and tree trunks, beside streams, or near cliffs, or waterfalls.
The fronds are 10 to 20 cm long, with 5 to 20 pairs of pinnae (leaflets), often fan-shaped or sometimes lanceolate.


Asplenium flaccidum is a species of fern in the family Aspleniaceae. The plant common name is drooping spleenwort or weeping spleenwort, and the species name flaccidum derives from the Latin root meaning drooping. An example occurrence of A. flaccidum is within a Nothofagus-Podocarp forest at Hamilton Ecological District on New Zealand's North Island in association with other fern species understory plants, crown fern, Blechnum discolor being an example.


A global phylogeny of Asplenium published in 2020 divided the genus into eleven clades, which were given informal names pending further taxonomic study. A. flaccidum belongs to the "Neottopteris clade", members of which generally have somewhat leathery leaf tissue. It forms a clade with A. appendiculatum and A. chathamense.


A. gracillimum individuals occasionally grow small bulbils on top of their fronds, which can fall off and grow into new ferns. There are a number of similar Southern Hemisphere species which have a similar mode of reproduction, including A. daucifolium and Polystichum australiense. Fronds range from 10.5 to 108 cm long. A. gracillimum has larger spores than A. bulbiferum, and fewer bulbils. The scales are ovate on A. bulbiferum, but narrower and almost always drawn out into thin threadlike points in A. gracillimum (filiform apices). The selected lectotype was Dannevirke, New Zealand.


The species is an allotetraploid hybrid between A. bulbiferum and A. hookerianum. It was previously known as Asplenium bulbiferum subsp. gracillimum.
A 2020 plastid phylogeny of Asplenium showed a sample of the species nested within a clade containing both of its parents.


The hen and chicken fern commonly grows in most bush areas in New Zealand. It thrives in many situations from shade to partial sunlight. Often seen in moist or rainforest areas in eastern Australia, occasionally as an epiphyte on tree ferns or tree trunks.


This small fern may be found two forms. The broad-pinnuled version's fronds have rounded ultimate segments while the narrow-pinnuled version has very fine and narrow ultimate segments.


Asplenium hookerianum is found in New Zealand (including the Chatham Islands) and Australia.


Found throughout the North and South Islands of New Zealand. Less common in Northland, inland Taranaki, western Waikato, King Country and the West Coast.
Its range extends to Stewart Island and the Chatham Islands although it is uncommon.
Occurs in lowland and montane forests, on shaded clay banks and rocky outcrops, in shrubland and open forest. May also be found among grass and in open pasture, under pine and macrocarpa trees, and in disturbed forest remnants.
In the South Island, it is mostly confined to lowland areas. In the North Island, it can reach altitudes of up to 1375 metres but is less common above 1000 metres on both islands.


Found in Tasmania and Victoria where an estimated 700 plants live in four wild populations. Little is known about the previous distribution of this species.
In Tasmania, it occurs in rainforest, usually on the heavily shaded margins of waterways and vertical banks. It may also be found in sheltered gullies within drier forests. Can also be found growing on the lower trunks of soft tree-ferns. They may reach altitudes of up to 500 metres.
In Victoria, it occurs on sheltered rock faces in cracks and crevices under overhangs. They may reach altitudes of up to 1,200 metres. Because of its preference for cold and wet environments, it may be impacted by climate change in the future.


First described by Raoul in 1844 as Asplenium adiantoides. This name was disregarded due to conflicting earlier homonyms. It was later described by Colenso in 1845.
It was named after British botanist Sir Joseph Dalton Hooker.
A global phylogeny of Asplenium published in 2020 divided the genus into eleven clades, which were given informal names pending further taxonomic study. A. hookerianum belongs to the "Neottopteris clade", members of which generally have somewhat leathery leaf tissue. It formed a clade with A. bulbiferum, A. cimmeriorum, and A. richardii.


Asplenium hookerianum produces spores that are dispersed by wind.


In New Zealand, A. hookerianum is listed as Not Threatened.
In Tasmania, it is listed as Endangered. In Victoria, it is listed as Vulnerable. Not much is known about the threats to A. hookerianum. Intensive farming, forestry, and cliff-based recreational activities such as abseiling and rock climbing may have some impact.


Asplenium hookerianum is easily grown and makes a good pot plant, though it is slow growing. It is prone to scale and mealy bug infestations. It is not commercially available.


Asplenium platyneuron (syn. Asplenium ebeneum), commonly known as ebony spleenwort or brownstem spleenwort, is a fern native to North America east of the Rocky Mountains. It takes its common name from its dark, reddish-brown, glossy stipe and rachis (leaf stalk and midrib), which support a once-divided, pinnate leaf. The fertile fronds, which die off in the winter, are darker green and stand upright, while the sterile fronds are evergreen and lie flat on the ground. An auricle at the base of each pinna points towards the tip of the frond. The dimorphic fronds and alternate, rather than opposite, pinnae distinguish it from the similar black-stemmed spleenwort.
The species was first described in 1753 by Linnaeus as Acrostichum platyneuros, although Linnaeus' type drew on material from several other species as well. It was more commonly called Asplenium ebeneum, a name published by William Aiton in 1789, until the rediscovery and revival of the Linnaean epithet in the late nineteenth century. Several forms and varieties of the species have been described, but few are recognized today; in particular, larger and more fertile specimens, those with more or less toothed leaves, and those with proliferating buds are considered to fall within the natural range of variation of the species, and do not require taxonomic distinction. A. platyneuron f. hortonae, a sterile form with the pinnae cut to toothed pinnules, and f. furcatum, with forking fronds, are still recognized.
The formation of proliferating buds is one of several unusual adaptations for reproduction in this species. The buds form near the base of the stipe, and when covered with soil, can grow into new individuals as the frond that bore them dies. Ebony spleenwort is also well-adapted to propagate by spores: the upright sterile fronds help the spores enter the airstream for long-distance dispersal, and a low genetic load allows spores that have grown into a gametophyte to self-fertilize with a high degree of success. This dispersal ability seems to have helped the species spread rapidly in the Great Lakes region in the late 20th century. Long-distance dispersal may also explain its naturalized appearance in South Africa, and the existence of an isolated population found in Slovakia in 2009, its first known occurrence in Europe.
Ebony spleenwort has broad habitat preferences, growing both on rocks like many other North American spleenworts and in a variety of soils. Unlike many other spleenworts, it is not particularly sensitive to soil pH. It hybridizes with several other spleenworts, particularly mountain spleenwort and walking fern; these species, their sterile hybrid offspring, fertile allotetraploid hybrids, and backcrosses between allotetraploids and the parents are collectively known as the "Appalachian Asplenium complex". Two hybrids between A. platyneuron and spleenworts outside of this complex are also known.


Ebony spleenwort is a small fern with pinnate fronds, growing in tufts, with a shiny reddish-brown stipe and rachis. The fronds are dimorphic, with long, erect, dark green fertile fronds, which are deciduous, and shorter, spreading, lighter green sterile fronds, which are evergreen.


This fern does not spread and form new plants via the roots. The rhizome, from 1 to 2.5 millimeters (0.04 to 0.1 in) or perhaps 4 millimeters (0.2 in) in diameter, bears a few narrowly linear-deltate scales, black to dark brown in color and strongly clathrate (bearing a lattice-like pattern). The scales are 2 to 4 millimeters (0.08 to 0.2 in) or 5 millimeters (0.2 in) long and 0.3 to 0.6 millimeters (0.01 to 0.02 in) wide, with margins entire (untoothed) or very nearly so.


The stipe (the stalk of the leaf, below the blade) is 1 to 10 centimeters (0.4 to 4 in) long, and comprises one-quarter to one-third of the length of the blade. It lacks wings, and is a shiny reddish-brown or blackish-brown throughout its length. Towards the base, it has a few threadlike scales similar in color to those of the rhizome. Starch granules are stored in tissue at the base of the stipe and, to a lesser extent, in the rhizome, giving the bases an enlarged appearance and a firm texture. The stipe bases are long-lived and may survive the disintegration of the rest of the stipe and the blade.
The leaf blade of ebony spleenwort is linear to narrowly oblanceolate (slightly wider in the upper half of the blade) in shape, measuring from 4 to 50 centimeters (2 to 20 in) long and from 2 to 5 centimeters (0.8 to 2 in) wide, sometimes as wide as 7 centimeters (3 in). It is acute (pointed) at its tip and gradually tapers at its base. The blade is shiny and has a few scattered hairs, or lacks them entirely. The rachis (leaf axis), like the stipe, is reddish-, purplish- or blackish-brown, shiny and hairless.
The blade is cut into pinnae (leaflets) throughout its length, from 15 to 45 pairs per leaf. The pinnae are distinctly alternate along the rachis. They are oblong (roughly rectangular) or quadrangular in shape, sometimes somewhat falcate and angled towards the leaf base, those in the middle of the leaf blade measuring from 1 to 2.5 centimeters (0.4 to 1 in) in length and from 0.3 to 0.5 centimeters (0.1 to 0.2 in) in width. Each pinna has an obvious auricle at its base, pointing towards the tip of the blade and overlapping the rachis. Sometimes a small auricle pointing at the base of the blade is present as well The edges of the pinnae are crenate or serrulate (bearing rounded or small sharp teeth); they are more deeply cut in small forms. The tips of the pinnae may be acute or obtuse (blunt. On the underside of the blade, veins are clearly visible and free (they do not anastomose or rejoin each other). A few minute scales may also be scattered on the underside.


Ebony spleenwort is capable of proliferating by forming new plantlets from buds on the rachis at the base of the plant. These allow new individuals to form at different levels when prostrate fronds become buried in the leaf litter. Wagner & Johnson found proliferous buds in almost every site in the Great Lakes populations they studied; very rarely did more than one bud per plant occur. They occurred, on average, on 1 out of 6 plants, both on sterile and fertile fronds, and their position at the base of the lowest pinnae made them difficult to find among the cluster of fronds. The buds are button-like, pale in color, and appear on the upper side of the lowest pinnae. Each bud contains a shoot and one or sometimes two leaf primordia, covered in clathrate scales, occasionally with roots if the bud has begun to develop. Contact with soil at the plant base stimulates their development, and the decay of their connection with the parental leaf results in the development of a new plant. Similar buds have also been reported from the single-sorus spleenwort, Asplenium monanthes.


The species most similar to Asplenium platyneuron is the black-stemmed spleenwort, A. resiliens. However, this stipe of this species is darker, and the pinnae are opposite, rather than alternate, along the rachis. Maidenhair spleenwort, A. trichomanes, is also pinnately cut with a dark, glossy rachis, but the pinnae are oval and somewhat rounded rather than broadly oblong, usually less than two times as long as wide. Neither of these two species, nor the other pinnate American spleenworts, have dimorphic fertile and sterile fronds. It is very similar to Boydston's spleenwort, Asplenium × boydstoniae, an extremely rare backcross with Tutwiler's spleenwort, Asplenium tutwilerae; however, Boydston's spleenwort has an elongated, acute frond tip similar to that of Tutwiler's spleenwort. Among similar South African spleenworts, A. lunulatum has proliferating frond tips, while A. monanthes has only one sorus on each pinna.
Among the larger ferns, A. platyneuron might be confused with a young Christmas fern, Polystichum acrostichoides, but that species is generally much larger and has a green, scaly stipe and rachis. Fishbone fern, Nephrolepis cordifolia is likewise larger, with yellowish-green pinnae and a green rachis.


This species is commonly known as "ebony spleenwort" or "brownstem spleenwort" for the dark color of its stipe and rachis.
The basionym for the species is Acrostichum platyneuros, published by Linnaeus in Species Plantarum in 1753 (the official starting point of modern botanical nomenclature). Linnaeus' treatment came from a 1745 dissertation by his student J. B. Heiligtag, which in turn drew on the descriptions by several earlier authorities. The first description listed was that of Jan Gronovius, botanist and mentor of Linnaeus, in his Flora Virginica of 1743, based on a specimen collected by the collector John Clayton. The specific epithet platyneuros ("flat nerves") was drawn from a description by the botanist Leonard Plukenet in his Almagestum of 1696. Unfortunately, only Clayton's specimen, now the lectotype for the species, represents the species now known as Asplenium platyneuron; the specimens upon which the other descriptions are based, including that of Plukenet which yielded the specific epithet, are a mixture of Pleopeltis polypodioides and Polypodium virginianum sensu lato. In 1789, the species was independently described by William Aiton in Hortus Kewensis, and given the name Asplenium ebeneum, referring to the ebony color of its stalk. The species was also independently described by Olof Swartz in 1801, as Asplenium polypodioides, and by André Michaux in 1803 as Asplenium trichomanoides; both these names were reduced to synonymy with Asplenium ebeneum by Carl Ludwig Willdenow. The name Asplenium trichomanoides, however, had already been used by Linnaeus in 1767, making Michaux's name a nomen illegitimum.
It was Aiton's epithet, ebeneum, that was used by American botanists throughout most of the 19th century. The transfer of Linnaeus' specific epithet to form the name Asplenium platyneuron was mooted by D. C. Eaton in 1878, who attributed the combination to a pencil notation by William Oakes in the margin of a copy of Flora Virginica. Therefore, the combination has historically been attributed to Oakes or Oakes ex D.C.Eaton. However, in 1981, David B. Lellinger pointed out that Eaton had not, in fact, accepted the combination in 1878, preferring the more descriptive epithet ebeneum to the less accurate through senior platyneuron. Eaton's use, therefore, was to be treated as provisional, and not as a published combination by him. Eaton aside, the first valid publication of Asplenium platyneuron was that of Britton, Emerson E. Sterns, and Justus F. Poggenburg in 1888, which implicitly references Linnaeus's basionym. Despite the revival of Linnaeus' epithet, the name Asplenium ebeneum continued to be widely used through 1896, when Lucien Underwood, in Britton & Brown's Illustrated Flora, used the name Asplenium platyneuron with explicit reference to the basionym.
The species has twice been placed in genera segregated from Asplenium: as Chamaefilix platyneuros by Oliver A. Farwell in 1931, and as Tarachia platyneura by Sizuo Momose in 1960. Neither combination was widely accepted and current authorities do not recognize these genera.
A global phylogeny of Asplenium published in 2020 divided the genus into eleven clades, which were given informal names pending further taxonomic study. A. platyneuron belongs to the "A. incisum subclade" of the "Schaffneria clade". The Schaffneria clade has a worldwide distribution, and members vary widely in form and habitat. There is no clear morphological feature that has evolved within the A. incisum subclade to define it, but members of the subclade do share a chestnut-brown stipe base. Relationships within the clade are not well-resolved; it includes species from South America, Europe, and China, but no other North American species.