The Great Horned Owl (Bubo virginianus) is one of the earliest breeding owls in North America. They are often heard calling to each other in the fall and breed in late January to early February. They often take over a nest used by some other large bird, sometimes adding feathers to line the nest. In the Sonoran Desert, they often take over abandoned Red-Tailed Hawk nests in the arms of a Saguaro Cactus. Sonoran Desert, Tucson, AZ.