Asio otus
long-eared owl

Long-eared owls are found throughout the northern hemisphere. Their range extends throughout temperate North America, through Europe and the former Soviet Union as far east as Japan. Isolated populations are also found North and East Africa, the Azores, and the Canary Islands.

Long-eared owls inhabit dense vegetation close to grasslands, as well as open forests shrub lands from sea level up to 2000 m elevation. They are common in tree belts along streams of plains and even desert oases. They can also be found in shelterbelts, small tree groves, thickets surrounded by wetlands, grasslands, marshes and farmlands.

Long-eared owls are medium-sized owls. Females are generally much larger than males, (260 to 435 g and 27 to 40 cm in length versus 220-305 g and 35 to 37.5 cm in length for males). Long-eared owls are the most slender of all North American owls, an attribute that they use as a defense against predators. When perched, long-eared owls elongate their body and ear tufts, and compresses its feathers, making them resembles a tree limb. Long-eared owls have long, rounded wings and a long tail. The wings are so long that they cross each other in the back when the bird is perched. The wingspan of adults ranges from 90 to 100 cm. The head of long-eared owls is large and round, topped with long blackish ear tufts that are close together and are not visible in flight.

Long-eared owls are brownish gray, with vertical streaks that distinguishing them from great horned owls, which have horizontal streaks. Long-eared owls have pale patches on the face that give the appearance of white eyebrows, and a white patch below the bill. They have a black bill, orange or yellow eyes, and their legs and toes are completely feathered.

Females are generally darker and more richly colored than males. Juveniles look similar to adults, but have softer, looser feathers.

Long-eared owls are monogamous, though polygyny is occasionally observed in this species. Pairs begin to form in winter, and breeding takes place from February to mid-July. Males advertise for a mate using songs and aerial displays, such as zig-zag flights through trees in the breeding habitat.

Long-eared owls breed between February and July, and raise one brood per season. Males begin advertising for a mate as early as January. They use songs and aerial displays to attract a female.

Long-eared owls nest in trees, usually in stick nests built by other species. They may occasionally build a nest of their own, or use a nest located in an old tree stump or on the ground, but this is uncommon. Once a nest is selected, the female lays 2 to 10 (usually 5 to 6) eggs at 2-day intervals. The eggs are white, smooth and glossy. The female incubates the eggs for 25 to 30 (usually 26-28) days. She never leaves the eggs uncovered during the day, though she takes short breaks at night. The chicks are semi-altricial, and are brooded by the female for at least 2 weeks. The young leave the nest at about 21 days, though they are still flightless (called branching), and reside in nearby vegetation. They begin making short flights at about 35 days old and become independent at 10 to 11 weeks old. The male provides food for the female and owlets throughout incubation and brood-rearing. Long-eared owls usually begin breeding at 1 year.

Long-eared owls breed between February and July. They raise one brood per season. Long-eared owls nest in trees in nests built by other species. Once they choose a nest, the female lays 2 to 10 (usually 5 to 6) eggs. She lays one egg every other day. The eggs are white, smooth and glossy. The female incubates the eggs for 25 to 30 (usually 26-28) days. She never leaves the eggs uncovered during the day, but she takes short breaks at night. The chicks are semi-altricial. The female broods them for at least 2 weeks. The young leave the nest when they are about 21 days old, but they cannot fly yet. They leave the nest by walking, and live on branches near the nest. They begin flying when they are about 35 days old. The male brings food for the female and chicks until the chicks become independent. This happens when they are 10 to 11 weeks old. Long-eared owls usually begin breeding at 1 year.

Female long-eared owls incubate the eggs and brood the semi-altricial chicks for at least two weeks. During incubation and brood rearing, the male provides food for the female and chicks. The male continues to feed the chicks until they become independent at 10 to 11 weeks old.

The oldest known wild long-eared owl lived 27 years and 9 months. Adult annual survivorship in Germany and Switzerland was estimated to be 69%.

Long-eared owls are strictly nocturnal. They live in pairs during the breeding season, but are tolerant of other long-eared owls, and often roost in groups of 2 to 20 during the non-breeding season. During the breeding season, long-eared owls defend only the area immediately surrounding the nest. Nests may be found in a loose colony, with closest nests only 14 m apart.

Some long-eared owls are migratory, while others spend the winter in the breeding range. Other long-eared owls appear to be nomadic, moving in response to fluctuations in food availability.

The home range size of long-eared owls appears to vary considerably between pairs, seasons and localities. Studies have estimated home range sizes between 0.7 and 20.25 square kilometers.

Long-eared owls use a wide repertoire of calls to communicate primarily during the breeding season. They are mostly silent at other times of the year. The most common vocalizations are soft musical hoots and single quavering hoots. When excited, long-eared owls may also shriek or whistle. Alarm calls are demonstrated by both sexes. Parents strongly defend their young, with vocalizations as well as a "crippled wing act" used as a lure. Threat displays are also used, generally directed at human intruders or predators rather than toward one another.

Long-eared owls have excellent hearing and vision that aids them in perceiving their environment and in catching prey.

Long-eared owls hunt almost exclusively at night and in open habitats. During brood-rearing, they may begin hunting before sunset. Long-eared owls are active search-hunters. They most likely capture prey using their excellent low-light eyesight and their superb hearing. Most prey are captured on the ground or from low vegetation.

Long-eared owls probably prey opportunistically on small mammals under 100 g. Their principal prey are voles and deer mice. Other small mammals taken include pocket mice, kangaroo rats, pocket gophers, shrews (genera Glarina, Cryptotis and Sorex), juvenile rabbits (genera Sylvilagus and Lepus) and juvenile rats. Long-eared owls also occasionally eat small birds, small snakes, and insects. After capturing prey, long-eared owls kill it by biting the back of the skull and then swallow it whole. Excess prey is stored at the nest during incubation and during the nestling stage.

There is no information available regarding how long-eared owls drink or obtain sufficient water.

Adult long-eared owls are preyed upon by many other raptors. Raptors that have been observed taking long-eared owls include great-horned owls, barred owls, golden eagles, red-tailed hawks, red-shouldered hawks, northern goshawks, eagle owls, common buzzards, and peregrine falcons. Incubating female long-eared owls have been killed by raccoons.

Long-eared owl nestlings are vulnerable to predation by porcupines, bull snakes, American crows, black-billed magpies, and several hawk species.

Roosting adults are difficult to see because their coloration, slender body and ear tufts help them to look like a branch of the tree that they are roosting in. When a predator approaches a nest, adult long-eared owls defend the eggs or young by circling the nest and snapping their bill at the predator, or dive-bombing the predator while making alarm calls. They may also pretend to be injured in order to draw the predator away from the nest. In some cases, adults from several nearby nests may all perform defense displays when a single nest is threatened.

Long-eared owls impact the local populations of their prey. They also host several external and internal parasites.

Long-eared owls help to control populations of rodents that are considered to be agricultural pests.

Long-eared owls have no known negative effect on humans.

Populations of long-eared owls are difficult to track. However, within the U.S., populations appear to be largely stable, with declines locally in some states, including New Jersey, Minnesota and California. Most deaths are probably due to starvation or predation, though destruction of vegetation and alteration of habitat are also potential causes of population declines. Adults are occasionally killed by cars or shot by hunters in the U.S., but this is not common.

Long-eared owls are protected under CITES Appendix II and the U.S. Migratory Bird Act. They are not federally endangered or threatened in the United States, but they are considered threatened in the state of Michigan.

Six subspecies of Asio otus are recognized. The population endemic to Madagascar is usually treated as a full species (Asio madagascariensis).