ABSTRACT
The great horned owl is common in most forest, grassland, and desert ecosystems of North and South America, where it is at the top of many terrestrial food chains. Great horned owls are not migratory, and during a year, adult owls may confine their activities to 600 ha or less. In the forested portions of its range, great horned owls generally nest in trees, often in old nests of other raptors or corvids, and sometimes in hollow trees. The best method for counting numbers of territorial great horned owls is systematic and replicated searches for hooting males. In deciduous forests, all large nests likely to be used by great horned owls can often be located from vehicles or aircraft prior to leaf emergence. If no horned owls are seen at the nest, it must be inspected for presence of eggs or young.
