Bird of the Month: Great Horned Owl
By Andy McCormick
PC: Mick Thompson (Great Horned Owl)
Scientific Name: Bubo virginianus
Length 22 in
Wingspan 44 in
Weight 3.1 lb (1400 g)
AOU Band code GHOW
Now is the time of year to keep your ears perked up for the hoo-hoo-HOO-hooo-hoo Good for you, me too call of the Great Horned Owl, probably the most widespread owl in North America which can be found in a variety of wooded sites. Its hooting is the quintessential sound of an owl at night, but it also makes other vocalizations such as clucks, screams, and squawks.These owls breed in winter and as part of courtship they will call in a duet at dawn or dusk. The hooting of the female is generally higher pitched than that of the male. After chicks hatch the adults remain mostly quiet.
The Great Horned Owl is a fierce predator. Its diet is made up of a variety of mammals including those as large as a hare and birds including hawks. It will also consume rodents and snakes. The Great Horned attacks with extremely powerful talons which first crush its prey. Then its hooked bill is so powerful it will sever the spinal column of even prey that outweigh the owl.
It is an early nester. The first eggs can hatch as early as January (Alderfer). The male initiates courtship with hooting and display flights as early as October and November (Houston, et al). Typically the Great Horned does not build its own nest, choosing instead to use the old nests of a Red-tailed Hawk, crow, heron, or other large bird species, but it will also nest in a broken tree stump or cave or on a cliff ledge (Kaufman). It adds little nesting material except pehaps a few feathers. A Great Horned Owl can reuse a nest and males have a high degree of filiopatry, fidelity to their nest site.
Usually two to three dull whitish eggs are deposited and the female incubates them for about a month. After hatching the owlets are dependent on the parents for food for several months even continuing to beg for food until the following fall (Houston, et al). However, they will begin to leave the nest to climb on nearby branches at around five weeks of age. At this stage the young owls are sometimes called “branchlings.” They can begin flights at around 9-10 weeks of age (Kaufman).
The Great Horned is a long-lived bird with some individuals reaching age 20 or more. It is highly adaptable to changing habitat conditions and can be found in almost any habitat in North America except the arctic, high altitudes and extreme desert (Houston, et al). It is named after the two tufts of feathers that resemble horns. Its genus Bubo is from the Greek buas, horned or buzo, to hoot.
Although the population of Great Horned Owls is thought to be robust, more research is needed to obtain more accurate information about them (Houston, et al). Their numbers are generally not counted in breeding bird surveys, which are held in April and May and count birds by ear, when these owls have usually stopped hooting. At this time there are no conservation measures required for the Great Horned Owl, a denizen of our woodlands which adds a spirit of wilderness when encountered.