<P> Whereas owls of any age are freely attacked by great horned owls whether nesting or not, when it comes to diurnal raptors, great horned owls are mainly a danger around the nest . They are often hunt diurnal raptors when they come across their often relatively conspicuous active platform nests during hunting forays in spring and summer, taking numbers of both nestlings and brooding adults . Again, like owls, diurnal raptors are attacked depending on the relative similarity of their habitat preferences to the owl . Cooper's hawks (Accipiter cooperii) and red - tailed hawks tend to be most vulnerable, as they prefer the same wooded edges frequented by great horned owls . Other diurnal raptors may be attracted to more enclosed wooded areas, such as sharp - shinned hawks (Accipiter striatus) or zone - tailed hawks (Buteo albonotatus), or more open plain and meadow areas, such as hen harriers (Circus cyaneus) and ferruginous hawks, but this is almost never a total insurance against predation as all of these are recorded prey . In a study of red - shouldered hawks (Buteo lineatus) and broad - winged hawk (Buteo brachyurus) s breeding in New York, despite their nesting in deeper woods than those that host these owls, the main cause of nest failure was great horned owl predation . Similarly, the great horned owl was the primary cause of nesting failure for both desert - dwelling Harris's hawks (Parabuteo unicinctus) and forest - dwelling northern goshawk in Arizona (39% and 40% of failures, respectively), wetland - inhabiting osprey (Pandion haliaetus) in Delaware (21% of failures) and peregrine falcons (Falco peregrinus) in the Western United States (27% of failures). The fact that many of the nests great horned owls use are constructed by accipitrids may lead to localized conflicts, almost always to the detriment of the hawks rather than the owls . While the young of larger diurnal raptors are typically stolen in the night, great horned owls also readily kill large adult raptors both in and out of breeding seasons, including osprey, northern goshawk and rough - legged buzzard . </P> <P> Great horned owls are frequently mobbed by other birds . Most accipitrids will readily mob them, as will falcons . Hen harriers, northern goshawks, Cooper's hawks, Harris's hawks, red - tailed hawks, Swainson's hawks, ferruginous hawks, red - shouldered hawks, American kestrels, peregrine falcons, prairie falcons (Falco mexicanus) and common ravens (Corvus corax) are among the reported species who have been recorded diving on great horned owls when they discover them . In Arizona and Texas, they may be mobbed by Mexican and western scrub jays (Aphelocoma wollweberi & californica) and western and Cassin's kingbirds (Tyrannus verticalis & vociferans). The most infamous nemesis of this owl, however, is the American crow, who seems to regard it with great scorn . Several incidences have been recorded of dozens or even hundreds of crows appearing to mob a great horned owl . Such daytime flights normally cover short distances; if the owl flies, it alights to the nearest secluded spot to escape its tormentors . If an owl alights on ground or on exposed branch or ledge, it may respond to swooping and stooping flights of corvids and raptors with threat display and raising of its wings . </P> <P> Great horned owls are some of the earliest - breeding birds in North America, seemingly in part because of the lengthy nightfall at this time of year and additionally the competitive advantage it gives the owl over other raptors . In most of North America, courtship is from October to December and mates are chosen by December to January . This species is strictly monogamous . During courtship in late fall or early winter, the male attracts the attention of his mate by hooting emphatically while leaning over (with the tail folded or cocked) and puffing up his white throat to look like a ball . The white throat may serve as a visual stimuli in the low light conditions typical of when this owl courts . He often flies up and down on a perch, while approaching the potential mate . Eventually, he comes to approach the female and tries to rub his bill against hers while repeatedly bowing . If receptive, the female hoots back when the pair meet but is more subdued in both her hoot and display . The male may convince the female by bringing her freshly caught prey, which they will share . While males often hoot emphatically for about a month or six weeks towards the end of the year, the period where females also hoot is usually only a week to ten days . Pairs typically breed together year after year and may mate for life, although they associate with each other more loosely when their young become mostly independent . Pairs rekindling their reproductive relationship in the winter may perform a milder courtship to strengthen pair bonds before producing young . </P> <P> Males select nesting sites and bring the females' attention to them by flying to them and then stomping on them . Nests with open access, considering this birds large size, as opposed to enclosed with surrounding branches, are preferred . Like all owls, great horned owls do not build their own nest . They nest in a wider variety of nest sites than any other North American bird . Many nests are in cavernous hollows of dead trees or their branches, especially in southern states in large trees along the edge of old - growth lots . In mountainous or hilly areas, especially in canyons of the southwest and Rocky Mountains, cliff ledges, small caves, and other sheltered depressions may be used . Owls living in prairie country, in the absence of other animals' nests, riparian trees or non-native trees or the bare ground of tree hollows or man - made structures, will use boulders, buttes, railroad cuts, low bushes and even the bare ground as nest sites . Ground nests have also been recorded in the midst of tall grasses in Florida and in the midsts of brushy spots on the desert ground . Even the burrow entrances of American badger and coyote dens have reportedly been used as nests, in spite of the inherent risk of sharing space with such potentially dangerous co-inhabitants . </P>

When is mating season for great horned owls