Great horned owl (Bubo virginianus)

Synonyms: Strix virginianus
KingdomAnimalia
PhylumChordata
ClassAves
OrderStringiformes
FamilyStrigidae
GenusBubo (1)
SizeLength: 46 - 63 cm (2)
Wingspan: c. 139 cm (3)
Weight910 - 2,500 g (2)
Top facts

The great horned owl is classified as Least Concern (LC) on the IUCN Red List (1) and is listed on Appendix II of CITES (4).

The great horned owl (Bubo virginianus) is a large and powerful bird of prey, with characteristic horn-like ear tufts from which it gains its common name (3) (5). The second largest owl in North America (3), the great horned owl also has a distinctive white ‘bib’, or throat patch, as well extraordinarily large yellow eyes and powerful, fully feathered talons (2) (3). The female is generally larger and heavier than the male (2) (5) (6) and also has a brood patch which is not present in the male. In general, the overall appearance of the male and female great horned owl is fairly similar (2).

The plumage of the great horned owl has an undertone of white to buff (6), which is suffused with darker shades of brown, grey-brown or black-brown (3) (5) (6). The throat is white or sometimes orange-buff, which is especially visible when the bird is perched or calling (5) (6). The underside of the body is buff, with light and dark brown barring and dark brown tips to the feathers (3) (5) (6).

On the face, the well-defined tawny facial disk is encircled by a narrow black band (2), and has two white ‘eyebrows’ above the eyes (2) (6). The bill is slate-coloured or black and is partially hidden within the facial feathers (6). The legs of the great horned owl are fully feathered and are mottled brown or buff (5) (6), while the tail is short and barred, with white edges (6).

Juvenile great horned owls look fairly similar to the adults, with a slightly more red-buff colouration (3) and softer, looser feathers, which are fluffy in appearance. The horn-like tufts on the head are shorter and the cinnamon-buff feathers on the head have paler tips. The breast and face of the juvenile great horned owl are much darker than in the adult, with more black and dark brown colouration (2).

There are at least 16 subspecies of great horned owl, all of which differ in size, as well as the colour and pattern of their plumage (2).

The characteristic territorial, hooting call of the great horned owl is a low-pitched, solemn ‘who-hoo-ho-oo’. The vocalisations of the male and female are similar, although the male’s are usually longer, deeper and more elaborate, with a different rhythm (2). When calling, the male will usually position itself on a high perch, inflating its throat to display the conspicuous white throat patch (5). 

The vast range of the great horned owl extends from the Arctic treeline in Canada and Alaska, south through the USA and Central America, and into South America (2) (7) (8). It is also sometimes recorded as a vagrant in Bermuda and Panama (7).

Occurring in a variety of different habitats, the great horned owl is found from the Arctic treeline in the north of its range to tropical rainforests in the south (9). Throughout its range, the great horned owl inhabits deciduous, mixed and coniferous forests, river valleys, lake shores and agricultural areas, as well as urban areas, where it is mostly found around golf courses and parks with an abundance of trees (2) (3) (8). The home range of the great horned owl usually includes open areas for hunting (2).

This wide-ranging bird is found up to elevations of 2,040 metres (8).

An opportunistic hunter, the great horned owl has a remarkably varied diet that includes insects, rabbits, hares, opossums, skunks, ducks, geese, herons, reptiles, frogs, fish and occasionally domestic cats (Felis catus) (2) (3) (5) (9). It has also been known to kill animals as large as porcupines (3).

A well-adapted predator, the great horned owl has large eyes which provide it with excellent night vision, making it perfectly suited for hunting at night. Although the eyes are unable to move within the eye socket, the neck of the great horned owl is able to rotate 180 degrees, giving it nearly all-round vision. The acute hearing of this bird enables it to detect its prey and its exceptionally soft feathers prevent it from being detected while flying (2). Hunting at night from an elevated position, the great horned owl is able to see its prey and then attack with its powerful talons. Excess food is stored within the great horned owl’s territory (5).

A generally nocturnal species (3), the great horned owl spends its days roosting in trees, bushes or crevices in cliffs (2) (5). Breeding pairs typically occupy the same territory, which they protect from intruders, becoming especially aggressive and territorial during the breeding season (2) (5). The pair establish and maintain their territory through vocalising (2).

One of the earliest species to begin nesting, the great horned owl begins breeding in late January in certain populations (3). The male and female vocalise together prior to mating, after which a nest is chosen at a suitable site (2) (3) (5). The nesting sites of the great horned owl are extraordinarily variable, and this species occupies a wider range of nest sites than any other bird in the Americas (2).The nest is usually the disused nest of another large bird species, but cavities in trees, cliffs and deserted buildings will also be used, and the great horned owl will also nest on the ground (2) (3) (5).

A single clutch of two eggs is usually laid, although the clutch size occasionally ranges between one and four eggs. The eggs of the great horned owl are dull and white with a slightly rough surface, and are incubated by the female for between 30 and 37 days, with the male feeding the female throughout this period (2).

Once hatched, the nestlings remain in the nest for between 6 and 7 weeks, and begin to fly between 10 and 12 weeks old (2) (5). The nestlings are voracious feeders and weigh around 75 percent of the total adult mass when they leave the nest, after which time they remain within close proximity to the adults until the end of summer or early autumn (2) (3) (5).

The great horned owl is a sedentary species and even the most northerly populations do not migrate (2) (3) (9). However, in times when food becomes scarce, individuals may move to areas where there is more abundant prey (9).

Once persecuted for being a pest to humans and agriculture, the great horned owl is now protected throughout its range and hunting is banned (2) (6), although some illegal shooting still occurs (2). Currently, its populations do not seem to have been affected by habitat loss, although in the future certain areas may not be able to provide the large home ranges and abundant prey required by this species (2) (5) (6).

The use of pesticides and rodenticides on agricultural land is known to contaminate the prey species of the great horned owl, which can cause poisoning (2) (5). Road traffic accidents and collisions with electric wires are also threats to this species (5).

As it is a common and widespread species (9), there are no specific conservation measures currently in place for the great horned owl, although artificial nesting sites are known to encourage its population growth in some areas (2). The great horned owl is listed on Appendix II of the  Convention on International Trade in Endangered Species (CITES), which means that any international trade in this species should be carefully controlled (4).

Find out more about the great horned owl:

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
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  1.  IUCN Red List (March, 2012)
    http://www.iucnredlist.org/
  2. Stuart, H.C., Smith, D.G. and Rohner, C. (1998) Great horned owl (Bubo virginianus). In: Poole, A. (Ed.) The Birds of North America Online. Cornell Lab of Ornithology, Ithaca. Available at:
    http://bna.birds.cornell.edu/bna/species/372
  3. Deal, K.H. (2010) Wildlife and Natural Resource Management. Delmar Cengage Learning, New York.
  4. CITES (March, 2012)
    http://www.cites.org/
  5. König, C. and Weick, F. (2008) Owls of the World. Christopher Helm Publishers, London.
  6. Smith, D.G. (2002) Great Horned Owl. Stackpole Books, Pennsylvania.
  7. BirdLife International (March, 2012)
    http://www.birdlife.org/datazone/speciesfactsheet.php?id=2214
  8. Campbell, R.W. et al. (1990) Birds of British Columbia.Volume Two.Nonpasserines:Diurnal Birds of Prey through Woodpeckers. University of British Colombia, Vancouver.
  9. Johnston, J.L. (2007) Home Range Analysis of Rehabilitated and Released Great Horned Owls (Bubo Virginianus) in Denton County,Texas, Through Radio Telemetry. M.Sc. Thesis, University of North Texas.