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Great Horned Owl Biology
A Reference for North and Central American Owls

Great Horned Owl - Bubo virginianus

Breeding Range Map  
Other Common Names: Virginia Horned Owl (virginianus); Dusky Great Horned Owl (saturatus); Montana Great Horned Owl (occidentalis); Northwestern Great Horned Owl (lagophonus); Labrador Great Horned Owl (heterocnemis); St. Michael Great Horned Owl (algistus); Western Great Horned Owl (pallescens) Pacific Great Horned Owl (pacificus); Tundra Great Horned Owl (subarticus); hoot owl; chicken owl; eagle owl; king owl.

Subspecies: Strictly speaking the Great Horned Owl is only found in the Americas. It has sometimes been considered to be part of the Eurasian Eagle-Owl (Bubo bubo) species that is spread across Eurasia. There are currently 8 recognized races of Great Horned Owl in North America. There are 4 races that have been described but further study will be required. There are also 2 races in Central America and 2 in South America (a third was recently divided into its own species).
B. v. lagophonus is found from Alaska south in the mountains to N. E. Oregon and as far east as W. Montana. The described race algistus is included here although both northern populations of races lagophonus and N. E. Canada's heterocnemis race may not be separable with the western race saturatus.
B. v. saturatus is found along the pacific coast from S. E. Alaska to N. California.
B. v. pacificus is found along the California coastline (except far north) and as far south as N. Baja California.
B. v. subarticus is found from E. British Columbia east to the Hudson Bay and south to at least the Northern U. S. The described race occidentalis of the Rocky Mountains has been included here. A mix with lagophonus or pallescens (or an unnamed race) may inhabit south to Arizona.
B. v. pallescens is found from C. and S. E. California east to W. Kansas and south to C. Mexico.
B. v. heterocnemis is found in N. E. Canada south to the Great Lakes. The described race scalariventris of Ontario and E. Manitoba has been included here.
B. v. virginianus is found from Minnesota south to E. Texas and east to the Atlantic from Prince Edward Island to Florida.
B. v. elachistus is found in Baja California.
B. v. mayensis is found on the Yucatan Peninsula.

Measurements and Weights:
Wingspan: 50 - 60 in.
Length: 18 - 25 in.
Tail: 6.9 - 9.9 in.
Average Weight:
Male: 46 1/2 oz.
Female: 61 oz.

Description: The Great Horned Owl is a large, powerful, and mostly nocturnal owl. It is also the only large owl with ear tufts. The smaller, medium sized Long-Eared Owl is similar in appearance although can be distinguished by its smaller size, slimmer shape, longer ear tufts, cross barred under parts, and different call (the Great Horned has a distinctive advertising hoot that 'might' only be confused with a Great Gray Owl). The Great Horned Owl is very widespread and common but can vary in color dramatically between regions although its markings do remain reasonably constant and it always has prominent ear tufts. Its under parts have thin dark brown bars on a whitish base with the upper chest bars becoming somewhat blotchy. The throat has a bold white patch; white mustache and white to tan along the sides of the bill into the eyebrows. The prominent facial disk is bordered at the sides with black. The eyes are from lemon yellow to straw colored with a thin black border. The backside has fine dark mottling with dark bars on the primaries and tail. The races tend to get smaller in size from the northeast to the southwest. The races also tend to blend with their habitat in their coloration. The owl varies in overall and facial disk color from whitish to orange-buff to brownish-gray to dark brown. The northern members of the subarticus race being the lightest with a whitish facial disk and overall whitish-buff base color. The darkest race being the saturatus with a deep brown facial disk, chest, and base color to its backside.

Young: The young are similar in coloration with the adults although their barring and dark markings are not as crisp and defined, ear tufts smaller or not apparent. It also has a screech similar to a barn owl for a call.

Habitat: The Great Horned Owl has probably the most diverse habitat and climatic tolerance of any North American owl. It inhabits virtually every type of terrain in North America form sea level to 11,000-ft. elevation. Of the three main requirements being nesting sites, available prey, and roosting sites the Great Horned is very adaptable. If there is a preferred habitat it would include mature deciduous woods with scattered conifers for maximum roosting concealment, that border water with adjacent open habitats for hunting.

Food and Feeding: The Great Horned Owl has such a long and diverse variety of prey that it would not be practical to list. It is a very opportunistic forager that generally chooses a perch and scans for prey although it will glide over areas where prey is likely to be, it will walk on the ground, and it has even been reported to wade into the water. Scarcely anything that moves is safe from this owl. It will eat prey as small as insects and scorpions or as large as domestic cats, woodchucks, geese, and Great Blue Herons. This owl's diverse diet may include small mammals to rabbits, birds, and reptiles to fish and amphibians. It will take carrion when the weather is bad. It has one of thee most powerful grips with its feet of any of the owls. It regularly preys on smaller owls and has been reported to attack and kill even Red-tailed Hawks. It has no predators and will eat anything from crayfish to young foxes.

Breeding: The Great Horned is the earliest nesting owl with breeding season from December to July depending on latitude. Because of its tremendously varied habitat, the Great Horned has developed flexibility in its nesting locations also. It usually nests in old stick nests of raptors or jays although depending on the habitat, it will also nest in caves, hollows of broken off snags, cliff ledges or faces, rock outcrops, abandoned quarries, crotches in cacti or holes in them, to mention but a few. Clutch size is normally small; 1 - 3 eggs (usually 2) but can have as many as 6 in years of abundant food. Incubation lasts 28 - 35 days (maybe temperature dependant). The young climb out on nearby branches at 5 - 6 weeks of age but do not fly well until they are about 10 weeks old. Subsequent parent care lasts for up to 5 months.

Movements and Life Span: The Great Horned Owl is generally regarded as sedentary except in the north of its range. Studies in Canada (Saskatchewan) show 17 of 35 recovered birds moving more than 150 miles with young birds more prone to travel than adults. Southern populations move very little. The Great Horned have potential for a very long life. Multiple studies show post-fledging mortality for the Great Horned is very high especially in the first 2 years of life. Natural causes include parasitism, disease, and starvation. Unfortunately the major causes of death are related to mankind with 52 - 86% of deaths in some banding studies caused by shooting and 19% by trapping (96% potentially intentionally caused by man). Other studies show 21% shooting deaths, 15% trapped, 20% hit by cars, and 7% electrocuted. Road kills, pesticides, illegal shootings, and electrocution are major causes of death in North America. The Great Horned Owl has a maximum recorded longevity record of more than 28 years.

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