Great Horned Owl

The great horned owl (Bubo virginianus), also known as the tiger owl (originally derived from early naturalists' description as the "winged tiger" or "tiger of the air") or the hoot owl, is a large owl native to the Americas. It is an extremely adaptable bird with a vast range and is the most widely distributed true owl in the Americas. Its primary diet is rabbits and hares, rats and mice and voles, although it freely hunts any animal it can overtake, including rodents and other small mammals, larger mid-sized mammals, birds, reptiles, amphibians, and invertebrates. In ornithological study, the great horned owl is often compared to the Eurasian eagle-owl (Bubo bubo), a closely related species which, despite the latter's notably larger size, occupies the same ecological niche in Eurasia, and the red-tailed hawk (Buteo jamaicensis), with which it often shares similar habitat, prey and nesting habits by day and is thus something of a diurnal ecological equivalent. The great horned owl is one of the earliest nesting birds in North America, often laying eggs weeks or even months before other raptorial birds.
== Description ==
The great horned owl is generally colored for camouflage. The underparts of the species are usually light with some brown horizontal barring; the upper parts and upper wings are generally a mottled brown usually bearing heavy, complex darker markings. All subspecies are darkly barred to some extent along the sides as well.
There is a variable sized white patch on the throat. The white throat may continue as a streak running down the middle of the breast even when the birds are not displaying, which in particularly pale individuals can widen at the belly into a large white area. South American horned owls typically have a smaller white throat patch, often unseen unless actively displaying, and rarely display the white area on the chest. There are individual and regional variations in overall color, with birds from the subarctic showing a washed-out, light-buff color, while those from the Pacific Coast of North America, Central America and much of South America can be a dark brownish color overlaid with blackish blotching. The skin of the feet and legs, though almost entirely obscured by feathers, is black. Even tropical great horned owls have feathered legs and feet. The feathers on the feet of the great horned owl are the second longest known in any owl (after the snowy owl). The bill is dark gunmetal-gray, as are the talons.
All great horned owls have a facial disc. This can be reddish, brown or gray in color (depending on geographical and racial variation) and is demarked by a dark rim culminating in bold, blackish side brackets. This species' "horns" are tufts of feathers, called plumicorns. The purpose of plumicorns is not fully understood, but the theory that they serve as a visual cue in territorial and socio-sexual interactions with other owls is generally accepted.
The great horned owl is the heaviest extant owl in Central and South America and is the second heaviest owl in North America, after the closely related but very different-looking snowy owl. It is heavily built, with a barrel-shaped body, a large head and broad wings. Its size can vary considerably across its range, with interior Alaskaand Ontario populations being largest and populations in California and Texas being smallest, though those from the Yucatán Peninsula and Baja California appear to be even smaller. Adult great horned owls range in length from 43 to 64 cm (17 to 25 in), with an average of 55 cm (22 in), and possess a wingspan of 91 to 153 cm (3 ft 0 in to 5 ft 0 in), with an average of 122 cm (48 in). Females are somewhat larger than males. Mean body weight is 1,608 g (3.545 lb) for females and 1,224 g (2.698 lb) for males. Depending on subspecies, maximum weight can reach 2,503 g (5.518 lb).
The wing chord length is 297–400 mm (11.7–15.7 in). The wing loading, the measured wing area in cm2 calculated against grams of weight, is high, meaning the wings are relatively small in surface area for the bird's weight; the species' wing loading has been described as proportionately the highest among raptors. The tail, being relatively short as is typical of most owls, is 175 to 252 mm (6.9 to 9.9 in) long.
The legs, feet and talons are large and powerful. Tarsal length is 54–80 mm (2.1–3.1 in). The average foot span of a fully spread foot, from talon to talon, is around 20 cm (7.9 in), as compared to 8 cm (3.1 in) in long-eared owls, 13 to 15 cm (5.1 to 5.9 in) in barn owls and 18 cm (7.1 in) in the great grey owl. Great horned owls can apply at least 300 pounds per square inch (PSI) of crushing power in their talons, a PSI considerably greater than the human hand is capable of exerting. In some big females, the gripping power of the great horned owl may be comparable to much larger raptor species such as the golden eagle.
The hard, inflexible bill of the great horned owl is 3.3–5.2 cm (1.3–2.0 in) long, although the culmen, the exposed bill portion as measured along the top of the beak, is only 2.1 to 3.3 cm (0.83 to 1.30 in).
The outer ear openings, which are concealed by feathers on the sides of the head, are relatively smaller than that of the Eurasian eagle owl, being 2.3 cm (0.91 in) in vertical axis, with the left ear slightly larger than the right.
The great horned owl's eyes, just slightly smaller than the eyes of a human being, are large even for an owl and rank proportionately among the largest eyes of all terrestrial vertebrates. They are visually highly adapted for nocturnal hunting and provide a wide, almost completely binocular field of view, a large corneal surface and a predominantly rod retina. Instead of turning its eyes, an owl must turn its whole head and the great horned owl is capable rotating its neck 270 degrees. The irisis yellow, except in the amber-eyed South American great horned owl (B. v. nacurutu).
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