Owls: Strigidae

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OWLS: Strigidae

EASTERN SCREECH-OWL (Otus asio): SPECIES ACCOUNTS
BARRED EAGLE-OWL (Bubo sumatranus): SPECIES ACCOUNTS
SNOWY OWL (Nyctea scandiaca): SPECIES ACCOUNTS

PHYSICAL CHARACTERISTICS

These owls are often called the "typical" owls. They have typical owl traits including a large, rounded head and forward-facing eyes set in a facial disk, an arrangement of feathers that focuses sound into the ears. They are adapted for night hunting, with eyes that see well in low-light conditions, very sensitive hearing, strong feet, and sharp talons (TAL-unz). Many members of this family have ear tufts on top of their heads. These are just feathers, not used for hearing. Typical owls differ from the family Tytonidae, barn owls, in several ways. Many have yellow eyes, and the facial disk is round rather than heart-shaped.

GEOGRAPHIC RANGE

Representatives of the family can be found on every continent except Antarctica. In contrast to tytonids, which are found only in regions where the climate is mild, some typical owls live in very cold climates.

HABITAT

Typical owls can be found in almost every type of habitat, but 95 percent are forest dwellers. The term "forest" covers a wide range of habitats, from tropical rainforest to boreal evergreen forest.

DIET

Small mammals such as voles are the most important food item for many typical owls. The type of prey taken varies with size. Small owls eat mostly insects but may also take small birds, reptiles, and amphibians. The largest owls, the eagle-owls, may take such large animals as rabbits, hares, and pheasants. The group called fishing owls eats fish almost exclusively.

BEHAVIOR AND REPRODUCTION

Most typical owls hunt by sitting on an elevated perch while watching and listening for prey. Exceptions to this hunting style include Northern hawk owls, which hunt like falcons, chasing other birds on the wing. Long-eared and short-eared owls patrol for prey by flying low and slowly over fields. In winter, great gray owls detect voles not by sight, but by the sounds they make under the snow, then plunge-dive. They can break through snow crusts thick enough to support a man.

Many typical owls make classic owl "hoo-hoo" vocalizations, but also use a variety of other vocalizations to communicate. Most typical owls are solitary night hunters. A few, such as long-eared owls, gather in groups in winter to roost. A few are active by day, including burrowing owls.

About 10 percent of all typical owls undergo true seasonal migration. The northern saw-whet owl is one example. Many species in northern regions move south in winters when their rodent prey are scarce.

Most strigids are monogamous (muh-NAH-guh-mus; having only one mate). In a few species (the boreal owl is one example), a male may take two mates simultaneously if food is plentiful. Most members of the group nest in tree cavities, shallow caves, or the abandoned nests of crows or hawks. A few species nest on the ground. Burrowing owls nest in the underground burrows of prairie dogs and other mammals.

NEW OWLS DISCOVERED

Owls are not well studied because they fly at night, and many species live in remote places, far from human dwellings. Scientists have had some owl surprises in recent years. One species of barn owl, the Congo Bay owl, was thought to be extinct. Then it was rediscovered in 1996 in Rwanda. In 2001, researchers discovered an entirely new species, never before known to science, in Brazil. It is called the Pernambuco pygmy-owl. Yet another new species, the Sumba hawk owl, was also discovered in 2001, on the Indonesian island of Sumba. All three species live in areas where forest is being cut down, however. Conservationists hope the news of owl discoveries will not be followed by news of their extinction.

The average clutch size is two to four, though eagle owls typically lay a single egg and burrowing owls can have clutches of ten or more when food is plentiful. The female incubates the eggs and broods the chicks while the male feeds the family. The young often leave the nest before they can fly to clamber around in the nest tree. At this stage they are called branchers.

OWLS AND PEOPLE

Through the ages, owls have been the subjects of myth, folklore, and art. People have used owls in different ways. Snowy owls are a subsistence food for Arctic people. Owl body parts are used by traditional healers in Southeast Asia. They have been revered in some cultures. In ancient Babylon, for example, pregnant women wore protective owl amulets. In many cultures, however, owls have been feared. The Swahili believed owls made children sick. Some Arab cultures believed owls were evil spirits that carried children off. In the twenty-first century, conservationists are working to overcome old superstitions and protect owls threatened by loss of habitat.

CONSERVATION STATUS

Six species in this family are considered Critically Endangered, facing an extremely high risk of extinction, six species are Endangered, facing a very high risk of extinction, and eight are Vulnerable, facing a high risk of extinction.

EASTERN SCREECH-OWL (Otus asio): SPECIES ACCOUNTS

Physical characteristics: Eastern screech-owls have ear tufts but often fold them flat, so they appear to have smooth, rounded heads. Individuals may be gray or rufous (red) in color. Rufous owls are more common in warm and moist climates such as the southern Appalachians. Gray owls are more common in northern regions and dry southern areas such as Texas. Research suggests gray birds survive better in heavy snow and cold temperatures.

Individuals range in length from 6.3 to 9.8 inches (16 to 25 centimeters). Females are slightly larger than males, and owls from northern regions tend to be larger than individuals in southern regions.

Geographic range: Eastern screech-owls are found throughout the eastern half of the United States and north into southern Canada.

Habitat: Screech-owls occupy a variety of habitats, from young to mature forests, and from lowlands and river valleys to mountain slopes. They also live alongside humans in suburbs and cities.

Diet: These small owls eat small prey, mostly invertebrates including insects, earthworms, and crayfish. Screech-owls in northern climates are more likely to take small mammals and songbirds.

Behavior and reproduction: The primary call is a distinctive, horse-like whinny that increases in pitch, then falls off gradually, ending with a trembling sound. When they are courting, males and females sing loud trilled duets.

Screech-owls usually nest in abandoned woodpecker holes. The female may lay two to six eggs. She incubates them for twenty-six to thirty-four days while the male brings food. The owlets fledge (grow feathers necessary for flying) twenty-five to twenty-seven days after hatching. Their parents continue to feed them for another eight to ten weeks.

Eastern screech-owls and people: Eastern screech-owls do well in suburban areas with mature trees and will use wooden nest boxes.

Conservation status: Populations tend to cycle naturally from high to low and back. Temporary declines are sometimes misinterpreted as evidence the species is in trouble. However, the IUCN does not consider this species to be threatened. ∎

BARRED EAGLE-OWL (Bubo sumatranus): SPECIES ACCOUNTS

Physical characteristics: The dark back is marked with reddish brown bars, contrasting with the barred, grayish white belly. The eyes are brown and the beak and feet are yellow. Barred eagle-owls have very noticeable ear tufts.

The group called "eagle-owls" includes the largest owls in the world. This species is a fairly small member of the group, 15.7 to 18.1 inches long (40 to 46 centimeters), a little smaller than the great horned owl.

Geographic range: Southern Myanmar, peninsular Thailand, south to Sumatra and Bangka Island.

Habitat: Tropical forests intersected by streams, secondary growth, plantations, and forested gardens.

Diet: Barred eagle-owls feed on large insects such as grasshoppers and beetles, along with small rodents, birds, and snakes.

Behavior and reproduction: The main call is a low-pitched "hoo." Pairs are thought to mate for life and may return to the same nest site year after year, often a natural tree cavity.

Barred eagle-owls and people: No particular significance to humans is known.

Conservation status: This species tolerates disturbed habitat and will nest around human homes. It is not considered threatened by the IUCN. ∎

SNOWY OWL (Nyctea scandiaca): SPECIES ACCOUNTS

Physical characteristics: This is the only mostly white owl. Males may be completely white; females have black bars on the back and belly. These heavy-bodied owls have very large, rounded heads and no ear tufts. The eyes are yellow and the dark beak may be hidden by feathers. Snowies are particularly well adapted to the cold. The legs and feet are completely covered with feathers. The feathers are unusually stiff, to keep out Arctic winds.

Geographic range: Snowy owls are found in a ring of habitat that circles the North Pole. In summer they breed on the tundra. In winter they may move as far south as the northern Great Plains of North America or north central Europe and Asia.

Habitat: Snowy owls nest on tundra. On their southward wanderings, they often frequent open, grassy areas such as airfields and golf courses.

Diet: Snowy owls feed almost exclusively on several kinds of Arctic voles and lemmings, species that undergo regular boom-and-bust population cycles. They sometimes take much larger prey, including ptarmigans and snowshoe hares, and often steal food from Arctic foxes. In a region where daylight can last for twenty-four hours during the summer months, they routinely hunt by day.

Behavior and reproduction: Snowy owls rarely vocalize outside of the breeding season. The typical call is a gruff, low-pitched hoot. They nest right on the ground, usually on a raised mound. A typical clutch has five eggs. The female incubates the eggs for thirty-one to thirty-three days while the male feeds her. The young leave the nest after twenty to twenty-eight days but cannot fly well until they are about fifty days old.

Snowy owls and people: In years that snowy owls wander south, their presence thrills bird watchers. A subsistence food for the Inuit, snowy owls may legally be hunted by all Alaska residents. In the twenty-first century, the snowy owl has been made popular by the success of the Harry Potter books and movies.

Conservation status: Snowy owls are not considered threatened by the IUCN, although populations in northern Europe seem to be declining somewhat. Populations are not well monitored. ∎