Species-Specific Management (SSM)

Great Horned Owl

The great horned owl, Bubo virginianus, is a fierce avian predator that represents the ultimate in strength and power among North American birds of prey. These owls are so pugnacious that they commonly overtake the nests of red-tailed hawks and bald eagles. Great horned owls have a wide variety of ecological and esthetic values.

In the past, these magnificent owls were shot and trapped because of the unfounded fears that people held of predatory species. Recently, citizens interested in wildlife have recognized the benefits of the great horned owl. The following list of management possibilities may help hold or attract an owl to a desired area.

1. Great horned owls in the southern Appalachian forests require large areas of forested habitat or woodlot containing mature trees (home range of approximately 300 hectares or 740 acres).
2. The birds are highly territorial and will attack any animal (owls, hawks, humans, etc.) that encroaches on their breeding territory. Densities average 1 pair per square mile. Therefore, do not expect to have many great horned owls in a given area. Other raptors may be excluded from an area by the owl.
3. Habitat quality is the primary controlling factor of population size. Populations tend to be very stable and widely distributed within proper habitat.
4. Large conifers are the best trees for roosting since they provide concealment and protection in all seasons. Large oaks that keep their leaves long into winter are also suitable for roosting. Allow trees meeting these criteria to reach maturity. Favored roosts are often trees that are segregated by size, type, or location from nearby trees.
5. Great horned owls rarely build a nest of their own since they simply commandeer the nests of other large raptors (particularly red-tailed hawks).
6. Nest sites can be a limiting factor if raptor nests do not exist. Building large nesting platforms patterned after red-tailed hawk nests is an alternative (such artificial nests are experimental).
7. Nesting areas near water consisting of about 8 hectares of wooded habitat are preferred, and these areas commonly include conifers. Look for these key areas and protect them along with water resources.
8. Snags, large hollow trees, cliff ledges, and caves provide alternate nesting sites. These areas must be protected. Doing so will also benefit other wildlife.
9. Great horned owls feed on the greatest variety of prey of any North American raptor. Rodents make up the largest percentage of their diet, but the opportunistic nature (they even eat skunks) of great horned owls reduces the detrimental effects of a fluctuating prey base. Snakes, bats, frogs, fish, insects, birds, and almost any small animal such as the squirrels and chipmunks will be eaten.
10. Proper management of prey habitat can ensure a food base. Great horned owls numbers have declined drastically in areas of extensive agriculture. "Clean farming" must be avoided. Shelter belts, woodlots, fence rows, brush piles, and all possible cover for prey must be preserved.
11. Prevent extensive cutting of mature forests. Dense forests intermingled with clearings are the favored habitat. Such areas provide nesting areas and an adequate prey base.
12. Creating clearings within large expanses of forest can improve prey populations (especially rodents, snakes, and lizards). Woodland edges are favorite hunting sites.
13. Hunting areas typically include woodland and open areas with scattered large trees for perching, and areas of this type must be preserved. The owls often prefer to hunt in mature forests without numerous small branches to obstruct their flight.
14. Prevent fires from destroying mature roosting and nesting trees.
15. Working to change human attitudes may be the most important activity for ensuring stable great horned owl populations. People must realize that all owls can be beneficial and are a natural part of the North American ecosystem. Human effects are the primary concern of managers. As much as 90% of owl mortality can be attributed to people. Therefore, tough laws must be enforced to protect these birds from human depredation.
16. Education is a must! Work with citizens' groups and encourage recognition of the benefits of owls. The misconception that owls decimate game bird populations must be corrected. Non-game species and rodents are the primary prey.
17. Managers and bird watchers wishing to increase great horned owl numbers must remember that the birds are highly adaptable to differing habitat conditions as long as nesting sites, roosting sites, and prey are available.
18. Studies are needed of the night-time environment, "profound cover", and relations of owl and other animal behavior to lunar forces.
19. Monitor the population changes and make adjustments in the expenditures based on the changes that occur in owls present, in their sign (re-gurgitated pellets or hair and bone), or in their sightings.
20. Human effects are of primary concern and must be properly managed. Anticipate how the forest will change, thus owls within it, and the effects on the populations, the prey base, and humans using the area. Can anything be done today to prepare for those anticipated changes?

A contribution of Mark D. Jones (1992) Department of Fisheries and Wildlife Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061

Submitted by Robert H. Giles, Jr.

This Web site is maintained by R. H. Giles, Jr.
Last revision July 17, 2002.