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Great Horned Owl Life History

Habitat

Habitat ForestsFound all across North America up to the northern tree line, Great Horned Owls usually gravitate toward secondary-growth woodlands, swamps, orchards, and agricultural areas, but they are found in a wide variety of deciduous, coniferous or mixed forests. In some areas, such as the southern Appalachians, they prefer old-growth stands. Their home range usually includes some open habitat—such as fields, wetlands, pastures, or croplands—as well as forest. In deserts, they may use cliffs or juniper for nesting. Great Horned Owls are also fairly common in wooded parks, suburban area, and even cities. Back to top

Food

Food MammalsGreat Horned Owls have the most diverse diet of all North American raptors. Their prey range in size from tiny rodents and scorpions to hares, skunks, geese, and raptors. They eat mostly mammals and birds—especially rabbits, hares, mice, and American Coots, but also many other species including voles, moles, shrews, rats, gophers, chipmunks, squirrels, woodchucks, marmots, prairie dogs, bats, skunks, house cats, porcupines, ducks, loons, mergansers, grebes, rails, owls, hawks, crows, ravens, doves, and starlings. They supplement their diet with reptiles, insects, fish, invertebrates, and sometimes carrion. Although they are usually nocturnal hunters, Great Horned Owls sometimes hunt in broad daylight. After spotting their prey from a perch, they pursue it on the wing over woodland edges, meadows, wetlands, open water, or other habitats. They may walk along the ground to stalk small prey around bushes or other obstacles. Back to top

Nesting

Nest Placement

Nest TreeGreat Horned Owls typically nest in trees such as cottonwood, juniper, beech, pine, and others. They usually adopt a nest that was built by another species, but they also use cavities in live trees, dead snags, deserted buildings, cliff ledges, and human-made platforms. In the Yukon they nest in white spruces with “witches’ brooms,” which are clumps of dense foliage caused by a fungus. They occasionally nest on the ground. Pairs may roost together near the future nest site for several months before laying eggs.

Nest Description

Nests often consist of sticks and vary widely in size, depending on which species originally built the nest (usually Red-tailed Hawks, other hawk species, crows, ravens, herons, or squirrels). Great Horned Owls may line the nest with shreds of bark, leaves, downy feathers plucked from their own breast, fur or feathers from prey, or trampled pellets. In some areas they add no lining at all. Nests deteriorate over the course of the breeding season, and are seldom reused in later years.

Nesting Facts

Clutch Size:1-4 eggs
Number of Broods:1 brood
Egg Length:2.1-2.2 in (5.3-5.6 cm)
Egg Width:1.8-1.9 in (4.5-4.7 cm)
Incubation Period:30-37 days
Nestling Period:42 days
Egg Description:Dull white and nearly spherical, with a rough surface.
Condition at Hatching:Helpless, with closed eyes, pink skin, and white down on upperparts.
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Behavior

Behavior Aerial Dive (ground/talons)Great Horned Owls roost in trees, snags, thick brush, cavities, ledges, and human-made structures. They are active mostly during the night—especially at dusk and before dawn. When food supplies are low they may begin hunting in the evening and continue into the early morning; in winter they may hunt during daylight hours. Mated pairs are monogamous and defend their territories with vigorous hooting, especially in the winter before egg-laying and in the fall when their young leave the area. Great Horned Owls respond to intruders and other threats with bill-clapping, hisses, screams, and guttural noises, eventually spreading their wings and striking with their feet if the threat escalates. They may kill other members of their own species. Crows, ravens, songbirds, and raptors often harass Great Horned Owls with loud, incessant calls and by dive-bombing, chasing, and even pecking them. Unattended eggs and nestlings may fall prey to foxes, coyotes, raccoons, lynx, raptors, crows, and ravens. Both members of a pair may stay within the territory outside of the breeding season, but they roost separately.Back to top

Conservation

Conservation Low Concern

Great Horned Owls are common and widespread throughout much of the Americas and they adapt well to habitat change as long as nest sites are available. Population size has been fairly steady between 1966 and 2019, according to the North American Breeding Bird Survey. Partners in Flight estimates the global breeding population at 5.7 million and rates it 8 out of 20 on the Continental Concern Score, indicating a species of low conservation concern. Great Horned Owls were heavily hunted until the practice was abolished in the mid-twentieth century, but some illegal hunting continues. Because of their prowess as predators, Great Horned Owls can pose a threat to other species of concern, such as Peregrine Falcons and Spotted Owls. Northern populations rise and fall in cycles along with prey populations. Owls are sometimes poisoned by pesticides and other toxic substances that have accumulated in their prey.

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Credits

Artuso, Christian, C. Stuart Houston, Dwight G. Smith and Christoph Rohner. (2013). Great Horned Owl (Bubo virginianus), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Lutmerding, J. A. and A. S. Love. (2020). Longevity records of North American birds. Version 2020. Patuxent Wildlife Research Center, Bird Banding Laboratory 2020.

Partners in Flight. (2020). Avian Conservation Assessment Database, version 2020.

Sauer, J. R., D. K. Niven, J. E. Hines, D. J. Ziolkowski Jr., K. L. Pardieck, J. E. Fallon, and W. A. Link (2019). The North American Breeding Bird Survey, Results and Analysis 1966–2019. Version 2.07.2019. USGS Patuxent Wildlife Research Center, Laurel, MD, USA.

Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, NY, USA.

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