Great Horned Owl - Bubo virginianus
Calls - Bubo virginianus
The Great Horned Owl was first seen in the Virginia colonies, so its species name was
created from the Latinised form of the name of this territory (originally named for Queen
Elizabeth I, the "Virgin Queen"). The first published description was made in
1788 by Johann Gmelin. Great Horned Owls are sometimes known as Hoot Owls, Cat Owls or
Winged Tiger.
Description: Great Horned Owls can vary in colour from a reddish brown to
a grey or black and white. The underside is a light grey with dark bars and a white band
of feathers on the upper breast. They have large, staring yellow-orange eyes, bordered in
most races by an orange-buff facial disc. The name is derived from tufts of feathers that
appear to be "horns" which are sometimes referred to as "ear tufts"
but have nothing to do with hearing at all. The large feet are feathered to the ends of
the toes, and the immature birds resemble the adults. Females are 10 to 20% larger than
males.
Size: Length 46-63.5cm (18-25") Wingspan 91-152cm (36-60")
Weight 900-1800g (32-63.5 oz)
Habits: Activity generally begins at dusk, but in some regions, may be seen in late afternoon or early morning. Both sexes may be very aggressive towards intruders when nesting.
Voice: Great Horned Owls have a large repertoire of
sounds, ranging from deep booming hoots to shrill shrieks. The male's resonant territorial
call "hoo-hoo hoooooo hoo-hoo" can be heard
over several miles during a still night. Both sexes hoot, but males have a lower-pitched
voice than females. They give a growling "krrooo-oo" or screaming note when
attacking intruders. Other sounds include a "whaaa whaaaaaa-a-a-aarrk" from
disturbed birds, a catlike "MEEE-OWww", barks, hair-raising
shrieks, coos, and beak snapping. Some calls are
ventriloquial. Most calling occurs from dusk to about midnight and then again just before
dawn.
Hunting & Food: Great Horned Owls hunt by perching
on snags and poles and watching for prey, or by gliding slowly above the ground. From high
perches they dive down to the ground with wings folded, before snatching prey. Prey are
usually killed instantly when grasped by its large talons. They also hunt by walking on the ground to capture
small prey or wading into water to snatch frogs and fish. They have been known to walk
into chicken coops to take domestic fowl. Rodents and small rabbits can be swallowed whole
while larger prey are carried off and ripped apart at feeding perches or at the nest.
Birds are often plucked first, and legs and wing tips discarded. An extremely wide range
of prey species (over 250 identified) are captured, but rabbits and hares are its
preferred prey. Mammalian prey includes all coexisting rodents, squirrels, mink, skunks,
raccoons, armadillos, porcupines, shrews, moles, muskrats, and
bats. They may sometimes take small domestic dogs and cats. Bird prey includes all other Owls (except Snowy Owl), grouse, woodpeckers, crows,
turkeys, pigeons, Red-tailed Hawks, bitterns, Great Blue Heron, ducks, swans, gulls, etc.
Reptiles include snakes, turtles, lizards, and young alligators. Amphibians include frogs,
toads, and salamanders. Other foods include fish, large insects, scorpions, centipedes,
crayfish, worms, spiders, and road killed animals. A Great Horned Owl is powerful enough to take
prey 2 to 3 times heavier than itself.
Pellets are very large, about 7.6 to 10.2 cm (3- 4") long and 3.8 cm
(1.5") thick. Pellets are dark greyish-black and compact. Skulls as wide as 3 cm
(1.2") are regurgitated whole. Pellets are regurgitated 6 to 10 hours after eating.
Breeding: Nesting season is in January or February when the
males and females hoot to each other. When close they bow to each other, with drooped
wings. Mutual bill rubbing and preening also occurs. They do not build a nest of their own
but utilise the nests of other birds such as the hawk, crow and heron. They may also use
squirrel nests, hollows in trees, rocky caves, clumps of witches broom, abandoned
buildings, or on artificial platforms. They are extremely aggressive when defending
the nest and will continue to attack until the intruder is killed or driven off. Normally,
two to four eggs are laid and incubated by the female only for 26-35 days. Young start
roaming from the nest onto nearby branches at 6 to 7 weeks, when they are called
"branchers", but cannot fly well until 9 to 10 weeks old. They are fed for
another few weeks as they are slowly weaned. Families remain loosely associated during
summer before young disperse in the autumn. Adults tend to remain near their breeding
areas year-round while juveniles disperse widely, over 250 km (150 miles) in the autumn.
Territories are maintained by the same pair for as many as 8 consecutive years, however,
these Owls are solitary in nature, only staying with their mate during the nesting season.
Average home ranges in various studies have been shown to be approximately 2.5 square kms
(1 square mile).
Mortality: A long-lived Owl, captive birds have been known to
live 29 to 38 years, and wild Owls up to 13 years. Most mortality is related to man -
shootings, traps, road kills and electrocutions. The only natural enemies are other Great
Horned Owls and, occasionally, Northern Goshawks during disputes over nest sites. Peregrine Falcons have also been observed attacking Great Horned Owls.
Habitat: Great Horned Owls have adapted to many different places and
climates. They occur in habitats from dense forests, deserts and plains to city parks.
They have been known to inhabit the same area as the diurnal red-tailed hawk.
Distribution: Great Horned Owls are found
throughout North America from the northern treeline and then in Central and South America.
They are resident year-round, however, birds living in the northern part of the species'
range may migrate south.
Distribution of Bubo virginianus
Status: Widespread and locally frequent.
Original Description: Gmelin, Johann Freidrich. 1788. Systema Naturae, 1, pt. 1, p. 287.
Subspecies:
B. v. virginianus,
B. v. elachistus,
B. v. heterocnemis,
B. v. lagophonus,
B. v. mayensis,
B. v. mesembrinus,
B. v. nacurutu,
B. v. nigrescens,
B. v. pacificus,
B. v. pallescens,
B. v. saturatus,
B. v. subarcticus,
B. v. wapacuthu,
B. v. deserti References:
Campbell, Wayne. 1994. "Know Your Owls (CD-ROM)". Axia Wildlife
Page Information:
Page compiled by Deane P. Lewis.
OwlPages.com Owl Species ID: 090.010.000 - Page last updated 2010-03-19
External Links:
Great Horned Owl - Bubo virginianus - Great Horned Owls at owling.com
Mark and Kim's Great Horned Owls - Photos and stories about Great Horned Owls nesting in the back yard of Mark and Kim Fabrizio.
Owls in the Brig - Follows the development of a Great Horned Owl nest on a power pole at Camp Pendleton Marine Corp Base, San Diego county, California.
The Neighborhood Owls - Photo gallery of a pair of Great Horned Owls at Bernal Hill, San Francisco.
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