Long-eared Owl

识别特征

This species is a rather slim and long winged owl with usually prominent erectile ear tufts, which are positioned closer to the center of the head than in many other types of owl. The purposes of ear tufts are not definitively known and are present in about half of living owls. Arguably the most popular theory amongst biologists and ornithologists is that ear tufts could be a means of intraspecies communication of intent and mood. In general coloration, the long-eared owl is often considered a hue of ochraceous-tawny with a grayish or brownish wash variably manifesting. The base color is commonly overlaid with variable blackish vertical streaks (and occasionally spots), which are usually more apparent about the wings and back. The scapulars are usually marked whitish, which provide further contrast when seen against the base color and blackish markings. The wing's dark carpal patches can also display broad panels of buff or almost orange on the wings across the base of primaries, which represent a more richly emphasized version of a pattern shared with other owls that tend to be vole-hunting specialists, like short-eared owls (Asio flammeus) and great gray owl (Strix nebulosa). On the underside, the body tends to be a somewhat paler ochraceous-tawny compared to the upperside. Long-eared owls tend to have dusky streaks on the upper breast, below which they may be heavily marked with herring bone pattern (which is created by dusky shaft-streaks and crossbars on these feathers). There is much individual and regional variation in markings with owls dwelling in more extensively forested regions tending to be of a darker hue, often so densely washed above as to appear largely dusky brown on the back and the underside largely overlaid with bolder dusky-blackish marks. Meanwhile, in some desert-like regions, the plumage may tend towards a somewhat more washed out look, at times appearing fairly cream or yellowish, with sparser and lighter dusky markings overall. The facial disc is visibly well developed and variably colored (see subspecies) in the species, rimmed dusky often with white running down along the center through the bill, while at times the white lines form a “moustache” and/or extending to the inside of the facial disc rim. The ear tufts are usually dusky in front and paler tawny on the back. Long-eared owl possess a blackish bill color while its eyes may vary from yellowish-orange to orange-red, tarsi and toes feathered.<p>The long-eared owl is a medium-sized owl, which measures between 31 and 40 cm (12 and 16 in) in total length. Their wingspan is relatively large for their size, measuring 86 to 102 cm (2 ft 10 in to 3 ft 4 in). However, compared to other widespread owls considered of medium size and to which they can appear broadly similar in size, such as barn owl (Tyto alba), short-eared owls and tawny owls (Strix aluco), the long-eared owl is quite a bit lighter and slenderer bodied, with mature weights around half of those of tawny owls not being uncommon. As expected in owls and birds of prey in general, long-eared owls display reverse sexual dimorphism in which females are usually slightly larger than males (to the contrary of most non-raptorial birds). Males furthermore may tend to be somewhat paler in plumage than females. In Finland, one survey of the body mass of mature birds found that 22 males averaged 288 g (10.2 oz) while 20 females averaged 327 g (11.5 oz). In body mass, European long-eared owls per a study were shown to run contrary to Bergmann's rule (that widespread animals should be smaller closer to the Equator) as body mass seemed to increase further south, being lightest in Sweden, where 37 males averaged 197 g (6.9 oz) and 24 females averaged 225 g (7.9 oz), intermediate in Denmark and heaviest in the Netherlands, where 21 males averaged 256 g (9.0 oz) and 24 females averaged 308 g (10.9 oz). In migratory owls largely from Scandinavian summer grounds in England, the average weight of 8 males was 263.6 g (9.30 oz) and the average of 28 females was 294.7 g (10.40 oz). Meanwhile, in various studies in North America, 38 males (in Montana) were found to average 245.3 g (8.65 oz), 55 males (also Montana in a different study) to average 261 g (9.2 oz) and 15 males (from Idaho) 232 g (8.2 oz). From the same studies, respectively, 28 females averaged 279.4 g (9.86 oz), 49 females averaged 337 g (11.9 oz) and 19 females averaged 288 g (10.2 oz). Museum specimens in North America were found to average 245 g (8.6 oz) in 38 males and 279 g (9.8 oz) in 28 females, while 520 migrating adults in Duluth, Minnesota averaged 281.1 g (9.92 oz). In all, long-eared owl males may vary in weight from 160 to 330 g (5.6 to 11.6 oz) while females may vary from 180 to 435 g (6.3 to 15.3 oz). <p>In standard measurements, long-eared owls vary in wing chord length from 262 to 315 mm (10.3 to 12.4 in) in males, with 883 in North America averaging 285.1 mm (11.22 in), and 255 to 332 mm (10.0 to 13.1 in) in females, with 520 American ones averaging 286.2 mm (11.27 in). The tail may measure 121.5 to 161 mm (4.78 to 6.34 in) in males and 143.5 to 165 mm (5.65 to 6.50 in) in females, with 1,408 owls averaging 146.3 mm (5.76 in). Less widely measured are bill length, which averaged 15.7 mm (0.62 in) in males and 16.2 mm (0.64 in) in females from North America, and tarsus length, which averaged 38.2 mm (1.50 in) in 20 males and 39.9 mm (1.57 in) for 16 females from Europe, with a range in both sexes of 36.9 to 42.3 mm (1.45 to 1.67 in). In terms of their skeletal structure, it bears a relatively wide skull but relatively small eyes and orbits, while the beak is relatively elongated but weak. The legs are relatively long and thin and, while needle-sharp, the talons are relatively fine and the feet relatively weak for an owl. However, the talons are still highly proficient at drawing blood if contact is made with human skin.<p>If seen well, an experienced observer is usually able to distinguish a long-eared owl by combination of its field marks, size and coloration. However, some potential owl species may be confused for them. The Stygian owl (Asio stygius) (which barely overlaps, perhaps in northern Mexico) is larger with partially bare toes and generally darker with inky and more boldly patterned plumage, with often nearly the enter facial mask appearing off-black. Tawny owls, which co-exist with long-eared owls in Eurasia, are unlikely to be mistaken given that they usually appear considerably rounder and bulkier overall (and are indeed slightly larger and much heavier), and possess a much broader, more rounded head. The tawny owl has no ear-tufts, eyes of blackish-brown colour and relatively shorter wings. In flight, tawny owls show well-fingered primaries (with five apparent emarginations) unlike the squared off wings of the long-eared owl. The Eurasian eagle-owl (Bubo bubo) is far larger and more massive than a long-eared owl with visibly more overdeveloped and powerful-looking feet and talons and a huge squared-off-looking head with the ear-tufts set nearer to the edge. The eagle-owl is often more heavily patterned on the crown and back with heavy blackish marking but has a less strongly demarcated (and shallower) facial disc when compared to the long-eared owl. In some parts of the wintering range, other eagle-owls may scarcely abut the wide range of long-eared owls in Eurasia (and perhaps northwestern Africa) but are usually distinguishable (similarly as in the Eurasian species) by size differences, plumage characteristics and, occasionally, habitat preferences. Asian fish owls, which are essentially a subset of eagle-owls, are generally also much larger than long-eared owls with tousled-looking ear-tufts, less variable coloring and often feathered over only part of their tarsi. In North America, great horned owls (Bubo virginianus), yet another type of eagle-owl in all but name, have a squarish head and more widely separated ear-tufts. Like other Bubo species, great horned owls are also perceptibly larger and more massively built than any long-eared owl (despite being smaller than the Eurasian eagle-owl). Great horned owls also have typically heavily barred, rather than streaked, underparts. Scops and screech owls are much smaller than long-eared owls, as well as differently marked (often with more individually varying overall coloring, i.e. from gray to brown to rufous) and usually having rather short ear-tufts. The Marsh owl (Asio capensis) (rare overlap, perhaps in northern Morocco) is generally brown with quite different-looking fine mottling or barring below and has brown eyes and tiny ear-tufts.<p>Over much of its range, long-eared owls occur with the related short-eared owl, the latter species averaging slightly larger. Much has been written about distinguishing them in the field, though, if seen well, the resemblance between the species is not particularly strong. Furthermore, the two species differ in habitat preferences, with the short-eared owl often favoring (where available) any kind of entirely treeless, open habitats (including many wetlands and Arctic tundra as well as steppe, prairie and extensive meadows), often avoiding the edge habitats favored by the long-eared owl. However, in dim light, at a distance or in flight, confusion is certainly possible. In both long-eared and short-eared owls, the flight style when seen has a distinctive, erratic and buoyant flapping quality that many birdwatchers consider reminiscent of a moth. At rest, the ear-tufts of the long-eared owl serve to easily distinguish the two (although long-eared owls can sometimes hold their ear-tufts lax). The iris-colour differs: yellow in short-eared, and often orange in long-eared. Furthermore, the black surrounding the eyes is vertical and slight on the long-eared, and horizontal and far more conspicuous on the short-eared. Overall, the short-eared owl tends to be a paler, sandier-looking bird than the long-eared, lacking the darker and more extensive markings of the latter. There are a number of other ways in which the two species differ which are best seen when they are flying. Short-eared owls often have a broad white band along the rear edge of the wing, which is not shown by long-eared owls. On the upperwing, the short-eared owl's primary-patches are usually paler and more obvious. The band on the upper side of the short-eared owl's tail is usually bolder than that of the long-eared. The short-eared's innermost secondaries are often dark-marked, contrasting with the rest of the underwing. The long-eared owl has streaking throughout its underparts, whereas on the short-eared the streaking ends at the breast. The dark markings on the underside of the tips of the longest primaries are bolder on short-eared owls. The upperparts of short-eared owls are coarsely blotched, whereas on the long-eared they are more finely marked. The short-eared owl also differs structurally from the long-eared, having longer, slimmer wings. The shorter and broader wings in combination with a squarer tail in long-eared owls produce proportions more reminiscent of a buzzard than the short-eared owl. When studied by their osteological features, however, the long-eared and short-eared owls are difficult to distinguish.<p>The long-eared owl has relatively large ear slits placed asymmetrically on the sides of its head, as in a majority of owls, with the left ear higher and right lower in order to allow them to absorb sound both from above and below. The ear slit very nearly occupy the full height of the skull, being are about 38 mm (1.5 in), long and covered in movable skin flaps. The right ear is about 13% larger based on freshly dead owls. Due to its ear structure, the hearing of a long-eared owl is around ten times better at hearing high and medium pitches than humans. Barn owls and boreal owl (Aegolius funereus) have (via convergent evolution) roughly similar ear structures, with the relative size of the ear structure and facial disc in owls generally indicative of the level of importance of acute hearing to their life history. Owls with relatively smaller ear slits and shallower or vestigial facial discs tend to skew towards more crepuscular or partially diurnal behaviors, whereas owls such as long-eared owls are more or less entirely nocturnal. It is well known that a majority of owls can hunt in darkness due to their extraordinary hearing, which allows them to pinpoint locations of prey, but they can also utilize their hearing to track intraspecific calls and activities and avoid predation risks.<p>The vocalizations of this species are highly variable. Amongst owls of all ages, long-eared owls in Michigan were recorded to have made 23 different vocalizations. Karel Voous considered them to likely be the most diverse vocalists of all owl species in the Northern hemisphere. The song of the male long-eared owl is a deep whoop, which is repeated at intervals of several seconds. It starts with some hoots at slightly lower pitch before reaching full volume and quality. On calm nights, this song may carry over up to 1 to 2 km (0.62 to 1.24 mi) away (at least to human auditory perception). The song of the male is around 400 hertz. In North America, some observers have considered the male's song as analogous to the deep cooing of band-tailed pigeons (Patagioenas fasciata). Females gives a weaker, less clear and much higher pitched song with a nasal quality. In nearly all owl species, the females, despite being typically the larger sex, have smaller syrinx than the males and so tend to have less powerful voices. The call of the female is at times compared to a weak tin whistle and is only audible at close range, being about 4-5 halftones higher than the song of the male. Females usually call only in duet with male during courtship, but also when the nest is selected and around the beginning of incubation (probably in conjunction with food-begging). In fact, close study has revealed that female calling may occur as frequently as every 2–8 seconds at times of night between nest selection and egg laying. Both sexes utter a cat-like, somewhat hoarse jaiow notes or high yip-yip notes, the latter reminiscent of a call made by barn owls. When disturbed near the nest holding young, both parents may utter a series of tinny tones, watt-watt-watt-watt. During the period of courtship the male flies around and flaps its wing around, producing a clapping sound. During the display flight, the male may make as many as 20 claps. As with many owls, all ages may produce hissing sounds and bill snapping when they feel threatened, especially in the context of nesting. Fledging young call all with high-pitched, drawn-out notes, variously transcribed as feek, peeyee and pzeei, and are often likened to the noise of a gate swinging on a rusty hinge.

分类信息

The long-eared owl was formally described by the Swedish naturalist Carl Linnaeus in 1758 in the tenth edition of his Systema Naturae under the binomial name Strix otus. This owl is now assigned to the genus Asio that was introduced by the French zoologist Mathurin Jacques Brisson in 1760.<p>Owls in the genus Asio are sometimes commonly referred to as eared owls. Despite their extensive distribution, only eight modern species are thought to exist. Four species are found both in Eurasia and Africa, and in the Americas, including the long-eared owl and short-eared owl. Despite similarities and being considered as in the same genus, it was found in a study utilizing electrophoresis that the genetic distance between long-eared owls and short-eared owls was unusually large for species within the same genera. Notwithstanding fossil records of Asio species showing their presence during prehistory in locations like Kansas and Idaho (Asio brevipes) and California (Asio priscus), the exact area of evolutionary origin of the long-eared owl is unknown and unlikely to ever be known. At least three modern species represent related derivations, possibly with long-eared owls as the paraspecies or as part of a species complex that potentially bears a basal common ancestor. In all three cases, the related owls are obviously more tropical in distribution and adapted to more humid conditions, with darker plumage, and larger bodies with apparently stronger feet and more overdeveloped talons, possibly exploiting a relatively unoccupied ecological niche against competing owls. One of these three is the Stygian owl, which is the darkest derivation of all and readily known to be distinct for some time. The other two slightly larger, tropical species, possibly housed in a species complex with the long-eared owl, were at one time considered to be part of the long-eared owl species. One of these is the Madagascar owl (Asio madagascariensis), obviously endemic to the island of its name, while the other is the Abyssinian owl (Asio abyssinicus), native to east Africa, especially in the northern area such as Ethiopia. While the marsh owl of Africa is outwardly very similar to and likely closely related to the short-eared owl, the striped owl (Asio clamator) is somewhat of an outlier among living Asio species and of mysterious origin. Despite being genetically related to the other living Asio species, it does not appear to be a close cousin. Studies of the mitochondrial genome found that the Asio genus, and consequently the long-eared owl, diverged most recently among living owl groups from the Otus or scops owl genus, with a more distant branch division from the Strix genus. A study of the genetic homogeny of long-eared owls in a single roost site was shown to be slightly higher than between different roosts. However, this homogeny is relatively low for a communal roosting bird in general.<p>Four subspecies of the long-eared owl are recognised:

学名

Asio otus

命名信息

(Linnaeus, 1758)

目

Strigiformes

科

Strigidae

属

Asio

分布与栖息地

The long-eared owl has an extremely large distributional range. In Eurasia, they are distributed from the Iberian Peninsula and the British Isles (including almost the entirety of Ireland), in both of which they are found somewhat spottily but quite broadly, especially for an owl. From western France east through the remainder of Europe they are found nearly everywhere. Though still usually quite common in these areas, there are small spots where they do not usually occur in Italy, Austria and Southeastern Europe. In Scandinavia they are found only as a breeding species in about the southern two-thirds of Norway, Sweden and Finland while they usual persist year around in haunts in the southern tips of Norway and Sweden, respectively, as well as in all of Denmark. In coastal Norway they are found at their worldwide northern limit as breeding bird, with long-eared owls nesting as far north as in the Subarctic zone of Troms. In latitudinal range, they are found as far south the Azores, the Canary Islands while their limited breeding range in north Africa is from Morocco to Tunisia, as well as seemingly in northernmost Algeria. Out of Europe, they are found very spottily as breeders in Turkey, northernmost Syria, Israel and Lebanon. They are quite broadly distributed within Russia, breeding in about the southern two-thirds of the country (north as far as roughly Chernyshevsky and Yakutsk) and often occurring year around in about the southern third of it (north to about the cities of Perm, Tyumen and Tomsk) and east to Siberia, ranging far as Sakhalin. Their range is continuous from Russia into most of Kazakhstan, Georgia, Kyrgyzstan, about half of Uzbekistan and infrequently into northern Afghanistan and Turkmenistan. In the east, they range through most of Mongolia (absent from the southwest) and the western and eastern parts of northern China, with seasonally uncertain status in the Koreas. Long-eared owls are found throughout the islands of Japan but mainly winter only in points south of Osaka. The long-eared owl occurs apparently only in winter in small spots of southern France, southern Greece, northwestern Egypt, northern Iran, southern Turkmenistan, broadly in much of Afghanistan, Pakistan and northern India (such as the Kutch, Punjab, Kashmir), as well as to the east in Bhutan, southern China, Taiwan and most of South Korea. Irruptive wanderings have resulted in vagrant long-eared owls in various places such as the Faroe islands, Iceland and Madeira as well as Ryukyu Islands in the east.<p>This species is found widely distributed in North America as well. Their northern limits are reached in much of British Columbia, though they are mainly absent from the western and coastal part, with the breeding range scarcely spilling over into the southern part of the Northwest Territories. As is the case in most of Eurasia, they are usually found at up to 50 degrees north. Long-eared owls are also found breeding in most of Alberta, all but northern Manitoba and southern Ontario and Quebec only to the southernmost part of the Hudson Bay. However, with the exception of inland southern British Columbia, southern Alberta, and the southern parts of Ontario and Quebec, as well as an isolated population in Newfoundland, long-eared owls usually vacate their Canadian range during winter. The species range as a breeding species is far more extensive in the west than the east within the United States. They breed in Washington, Montana and North Dakota mostly continuously to much of California, where habitat is appropriate, Arizona, western Colorado and western New Mexico as well as less broadly in South Dakota and Iowa. Even though they are absent from the Pacific coasts in Washington and Oregon, they may be found breeding along the Pacific in southern California and even Baja California in Mexico. The first record of breeding for mainland Mexico was recorded for an incidental observed nest built by owls in Janos Biosphere Reserve in Chihuahua. They also breed and occur year around in most of Minnesota, Wisconsin and Michigan. Breeding and/or year around occurrence is very rare in the eastern U.S. with a few records of them nesting in Maine, Virginia and West Virginia. The long-eared owl occurs much more broadly in North America during the non-breeding season and may found essentially all over the Midwest, Texas and as far south in Mexico as Colima, Veracruz and northern Oaxaca. The species also occurs in the non-breeding season in Louisiana (but for the southeast) and much of northern Mississippi, Alabama, Georgia and South Carolina north to Illinois, Indiana, Ohio and southern Pennsylvania. Very rarely, these birds have turned up in Florida (in times of exceptional irruption) and, as a vagrant, even the Bermudas. They are found also by winter and in migration in much of the east coast of the United States, from the Outer Banks in North Carolina, broadly in eastern Pennsylvania and almost anywhere in Delaware or New Jersey, southeastern New York (including New York City) and north to much of southern New England including almost all of Connecticut, Massachusetts and Rhode Island as well as southern New Hampshire.<p>Optimal habitat tends towards access to open spaces with short vegetation and abundant prey and wooded cover for roosting and nesting. In terms of attitudinal range, this species may live at many elevations with no strong altitudinal preferences noted, although they tend to be absent above the montane tree line. The species has been recorded exceptionally nesting at 2,700 m (8,900 ft) above sea level in Kashmir. Long-eared owls tend to inhabit usually rather open landscapes with groups of trees, hedges or small woods, as well as pastureland with rows of trees and bushes, any type of forest with clearings, forest edges, semi-open taiga forest, swampy areas and bogs, especially those with willows, alder and poplars, orchards with old fruit trees, parks, cemeteries with trees and bushes, even gardens and timbered areas in villages, towns or cities. In many parts of the world, including China, Israel and the American southwest, long-eared owls have shown the ability to adapt to deserts, though more commonly semi-desert, and may nest and roost in available oases and adapting to hunt prey over the open desert ground, whether it is sandy or more rocky. The preferred habitat in Great Britain was found to consist most regularly (amongst 200 nests) of small tree plantations, copses or scattered trees on moorlands, heath or mosses (33%), followed by blocks of forest (24.5%), smaller plantations, shelterbelts or hedgerows in various agricultural areas (24%) and scrub or wooded clumps near the coast and in wetlands (15%). All nests in Finland in a study were no more than 500 m (1,600 ft) from cultivated land and only occurred on margins of larger woods or forests. Ecological compensation areas (i.e. habitat for wildlife on privately owned farmland) in Switzerland did provide habitat for long-eared owls but it was found that voles were more extensively hunted in mowed sections of the lands rather than the more densely vegetated areas where voles were most abundant. This indicates habitat (in particular open ground habitat) is more important to the predators than prey densities, at least locally. In Spain, when compared to the little owl (Athene noctua), long-eared owls were more likely to be found in low disturbance areas where forest transitioned into plantations and to areas with a relatively low human presence. A preference by long-eared owls for stands of conifers has been noted in many American studies. In Ontario, the species breeds most often in dense conifer stands of wood and reforestation groves that are often somewhat wet, thence less often in mixed or deciduous areas. A similar association with conifers was observed aseasonally in Michigan. In North Dakota, dense thickets of small trees and brushy margins of more extensive forest tracts were the main habitat for these owls. In western areas where mixed woodlands may occur, however, deciduous stands may attract wintering owls, providing they have heavy growths of climbing vines. In the Sierra Nevadas, long-eared owls are often found in riparian zone of mixed woods around oaks and ponderosa pines (Pinus ponderosa). Analysis from Oregon has shown that forest management had no discernable effect on long-eared owls, indicating that they are not truly forest owls but clearances of riparian vegetation, conversion of foraging areas to agricultural fields and reforestation of open habitats did reduce local numbers. Despite being adaptable to both very cold areas, including the taiga and scarcely Subarctic, and quite warm areas, including drier and/or arid parts of the subtropics, the long-eared owl is largely confined to temperate zones of the north and is less climatically adaptable than the short-eared owl, with the latter species acclimating to nearly all climates and making its homes both in the Arctic and the tropics whether wet and dry so long as open habitats are available.

迁徙

Complete migrants

行为

Long-eared owls are more or less strictly nocturnal in activity. Usually activity for the species commences at dusk. After nightfall long-eared owls in Idaho were least active from 8-10 pm and from 5-6 am, while the hours around 10-12 pm and 3-5 am were often the peak times of activity. When living relatively close to the Arctic, long-eared owls may be forced to forage during daylight as no full nightfall may occur during summer. When flying by day, long-eared owls are often mobbed by diurnal birds such as corvids and other birds of prey. Often long-eared owls will discharge a fairly large amount of pellets and drop them below regular day roosts. Unlike most other owls, the species has no territorial hunting ground. In Switzerland, 14 long-eared owls examined using radiotelemetry were found to have an average home range of 980 ha (3.8 sq mi). In the study, they required fields along borders of woodlands, avoiding completely treeless areas more so than they were prevalent in the environment. In the České Budějovice area of Czech Republic, 9 radiotagged owls were studied. Nearly equal numbers were found in suburban and urban areas, and urban ones used developed areas for more than 50% of their nocturnal activity while suburban ones used developed areas for less than half of their activities. Similar habitats were favored by both urban and suburban owls but urban owls had to range wider to avoid heavy human activity and access city parks and so had larger average ranges, 446 ha (1.72 sq mi) vs 56 ha (0.22 sq mi), while suburban ones had easier access to meadows and stands of woods.<p>Out of roughly 19 regular species of owl in North America and 13 regular species of owl in Europe, the long-eared owl is classed as one of the five in both continents to be truly migratory, moving annually in at least some areas and in some numbers from summer to winter grounds and back whether or not it is an irruptive year. Northern populations are migratory, showing a strong tendency to wander south in autumn. Some normally young bird from central Europe migrate southwest at distances of up to more than 2,000 km (1,200 mi). Central European adults are less migratory, at most merely wandering in winter. Long-eared owls that breed Scandinavia generally migrate to nearly anywhere in Europe, from Great Britain to Southeast Europe, though some may disperse as far as north Africa or Asia Minor. In Europe, males and females seem to differ slightly in migratory behaviour. Long-eared owls wintering in Denmark were found to be heavily biased towards females, also there is a bias towards females in winter surveys in other areas such as southern Sweden. At 10 wintering sites in Europe, females were 36% more common than males. The hypothesis posited by those that studied the owls in Denmark is that females face a higher rate of predation by larger birds of prey and may distribute away from Fennoscandia where densities are high of those predators and to areas that show low densities of these predators. Another, non-exclusive, theory is that they may be avoiding areas with deep snow that may inhibit prey capture. Supporting data that male long-eared owls winter further north than females was gathered in southern Norway, where the recovery of dead owls (from car or powerline collisions) of the species encountered in late fall throughout winter, males were 45% more common than females. On evidence, many of the females that vacate Norway and even Fennoscandia come to winter in Great Britain (the female migrants here being up to 3.5 times more common during winter than male migrants in one study). Two birds in ringing studies that were recorded in late winter in Germany were observed to return for the summer to central Russia (near Yaroslavl, 2,050 km (1,270 mi) away) and to eastern Russia (near Kazan, 2,410 km (1,500 mi) away). Birds that breed in central Asia have been recorded to winter in a wide variety of locales, including the Egyptian Nile valley, Pakistan, northern India and southern China. In North America, migrants generally sourced from Canada and the Upper Midwest winter almost anywhere in the remaining United States, however they will irruptively migrate as far as Georgia and several areas of Mexico and seldom in Florida. Typically the northern limit of the wintering range fall up to the Okanagan Valley of British Columbia, the southern reaches of the Upper Midwest and central New England. Spring migration was tracked along with northern saw-whet owls (Aegolius acadius) as they migrated through Oswego County, New York via mist nets, with the saw-whet considerably outnumbering long-eared owls. Here, migration of long-eared owl was between March 21 and April 14 and, unlike the saw-whets, the long-eared owl migration does not appear to be effected as extensively by weather conditions. Long-eared owls are 19.5% of owls (or 197 total owls) recorded migrating through Cape May Point in fall (against a majority, 60.6%, being saw-whet owls), with 26.1% of the specimens from the species caught in the mist nets being adults. More than 90% of long-eared owls migrate between mid-October and late November, with the immatures migrating earlier, 52.1% of juveniles having passed through in October whereas only 9.4% of adults migrated in the month. Cape May studies also indicated that 58.87% of long-eared owls were caught in the dark before dawn rather than other times of night. Based on evidence from Cape May, migrating long-eared owls tend to fly higher above the ground than do migrating saw-whet and barn owls but not as high as the short-eared owl, with the latter owl often able to avoid mist nets apparently via its flying height while moving through. Per a study in Idaho, 7 radio-tagged owls actually migrating both north, 75 to 125 km (47 to 78 mi) north of their respective nesting sites, and to higher elevations after the breeding season (in many cases possibly to exploit displaced rodents in recently logged areas).<p>The long-eared owl has the peculiar ability to increase populations and then disperse in nearly multi-directional movements during good years for prey numbers. Banding records across North America show highly erratic numbers and movements across the continent of North America with unpredictable peak numbers of migrants in completely different years respectively for the states of Wisconsin, Michigan, New York and New Jersey. Therefore, the species is sometimes considered “nomadic” despite many populations of the species being consistent annual migrants. Similar tendency towards so-called “nomadism” is shared by other widespread raptors semi-specialized to hunting voles over open ground, such as short-eared owls and hen harriers (Circus cyaneus). These erratic movements and peaks and ebbs of northern populations has lent to descriptions of the long-eared owl as “irruptive”, however it generally moves in quite different ways from owls largely endemic to the taiga (or tundra), which are more traditionally irruptive in that they tend to migrate little or not at all when prey remain ample in their native home range but then move south in mass when prey populations crash. Long-eared owls, unlike these irruptive northern owls, often migrate from the northern areas regardless of conditions. However, like the northern irruptive owls, long-eared owls tend to appear in unprecedented numbers to the south when a peak prey year is followed by a winter during which prey population crashes. In North America, the migratory habits of long-eared owls are strongly mirrored by those of northern saw-whet owls. Study of banding records in Saskatchewan show that the long-eared owl Canadian populations may be considered more truly irruptive species both as a breeder and migrant in that only appears in numbers during peak vole years, with large numbers only in 4 of 44 banding years. During 7 low years, the long-eared owls of Saskatchewan seemed to disappear altogether from much of the province. Peak years also coincided often with snowshoe hare (Lepus americanus) peaks, possibly due to lessened competition (as the larger owls favored prey is locally the hare) and interspecific predation by great horned owls. The phenomena of movements that seem to be nomadic or purportedly irruptive in nature may occur as well in Europe, though given the species' denser population in general there in comparison to North America may result in less noticeable wide variations in numbers. Years with irruptive numbers of long-eared owls have been noted in the British Isles when prey peaks then crashes back in Scandinavia, resulting in much larger numbers of migrant long-eared owls into the islands than normal, as well as concurrently large numbers of short-eared owls and harriers. In southern Finland during a peak prey year followed by a prey crash, a very large number of long-eared owls were detected and were seen to be likely food stressed, as several were foraging actively during daylight despite the extensive nighttime hours during the season.<p>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, the long-eared owl often stays close to the same tree or grove of trees (i.e. in and around parks, large gardens, or cemeteries). Usually, when approached, the owl 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 may form aggregations of owls while roosting. Such groupings may include 6 to 50 owls, 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.

保护状况

种群趋势

declining