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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 ConcernGreat Horned Owls are common and widespread throughout much of the Americas, however populations declined throughout their range by about 33% between 1966 and 2015, according to the North American Breeding Bird Survey. Canadian populations had even greater declines - over 2.5% per year during those years - resulting in a cumulative loss of 72%. Partners in Flight estimates the global breeding population at 6 million with about 45% of in the U.S., 14% in Canada, and 7% in Mexico. The species rates an 8 out of 20 on the Continental Concern Score and is not on the 2016 State of the Birds Watch List. Great Horned Owls were heavily hunted until the practice was abolished in the mid-twentieth century. Some illegal hunting continues. Northern populations rise and fall in cycles along with prey populations. The species adapts well to habitat change as long as nest sites are available. In the Pacific Northwest they have expanded into open land recently created by logging. 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. Owls are sometimes poisoned by pesticides and other toxic substances that have accumulated in their prey. Back to top

    Backyard Tips

    Consider putting up a nest box to attract a breeding pair. Make sure you put it up well before breeding season. Attach a guard to keep predators from raiding eggs and young. Find out more about nest boxes on our Attract Birds pages. You'll find plans for building a nest box of the appropriate size on our All About Birdhouses site.

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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.

    IUCN. IUCN Red List of threatened species (Version 2012.2) 2012. Available from http://www.iucnredlist.org.

    Lutmerding, J. A. and A. S. Love. Longevity records of North American birds. Version 2015.2. Patuxent Wildlife Research Center, Bird Banding Laboratory 2015.

    Partners in Flight. 2017. Avian Conservation Assessment Database. 2017.

    Sauer, J. R., D. K. Niven, J. E. Hines, Jr. Ziolkowski, D. J., K. L. Pardieck, J. E. Fallon and W. A. Link. The North American breeding bird survey, results and analysis 1966-2015 (Version 2.07.2017). USGS Patuxent Wildlife Research Center 2017.

    Sibley, David Allen. 2014. The Sibley guide to birds, second edition. Alfred A Knopf, New York.

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