Spring to early summer is the time of year when most North American bird species elect to nest. Great horned owls take exception to that rule and, as contrary as it may seem, these “wise” nocturnal hunters begin their pre-mating rituals in November and December.
Why would any bird choose to nest during the coldest and snowiest months of the year? The answer to that question may be partially linked to how and where great horned owls prefer to nest. Rather than building their own nests great horned owls often use abandoned nests of other birds and sometimes squirrels. Because they nest in winter, great horned owls do not have competition for nesting sites from other birds. As spring approaches, eagles, crows, herons, magpies, and other large birds may return to last season’s nest site only to find that a great horned owl has moved in. Most birds, including eagles, will not contest the owl’s presence in their former domicile.
From November to December, male great horned owls do a lot of hooting during the early evening and pre-dawn hours as they are establishing breeding territories. After a brief courtship, a bonded pair will mate and select a nest site.
Eggs are laid one at a time in two-day intervals until an average clutch size of three to four is reached. Though both sexes incubate the eggs, it is the female that spends most of the time on the nest. Each egg hatches 26-35 days from the time it was laid. The owl chicks will remain in the nest (nestling phase) for 6-8 weeks. When the young birds first fledge (leave the nest), they usually do not go far and will remain in the care of the parents for as long as another 3 months.
The great horned owl is the most common and widespread owl found in Colorado. It occupies a variety of habitats from coniferous forests just below 10,000 feet to riparian woodlands of the eastern plains.