<P> More so than diurnal varieties of raptor, fairly significant numbers of owls are hunted, as all species are to some extent nocturnal and thus their corresponding activity can attract the horned owl's unwanted attention . The extent of predation on other owls depends on the habitat preferences of the other species . Eastern and western screech owls may be most vulnerable since they prefer similar wooded edge habitat . In a block of Wisconsin, great horned owls were responsible for the failure of 78% of eastern screech owl's nests . Long - eared owls and, to a lesser extent, barn owls tend to hunt in open, sparsely treed habitats more so than great horned owls, but since they may return to wooded spots for nesting purposes, they may be more vulnerable there . The long - eared owl and barn owls are often compared to the great horned owl as these medium - sized species often occur in abutting habitats and often hunt primarily the same vole and mice species, although the alternate prey of the great horned tends to be much larger, including the smaller owls themselves . In a pair of studies from Colorado, the average weight of prey for long - eared owls was 28 to 30 g (0.99 to 1.06 oz), 46 to 57.1 g (1.62 to 2.01 oz) for barn owl and 177 to 220 g (6.2 to 7.8 oz) for the great horned owl . Both young and adult great grey owls, despite their superficially superior size, are apparently hunted with impunity by great horned owls . In the boreal forests, both the northern hawk owl and great grey owl appear to be in greater danger of great horned owl predation in years where the snowshoe hare have low populations . Great horned owls were the leading cause of mortality in juvenile spotted owls (30% of losses) and juvenile great grey owls (65% of losses). Less is known about relations with the snowy owl, which may compete with great horned owls for food while invading south for the winter . Anecdotally, both snowy and great horned owls have rarely been reported to dominate or even kill one another depending on the size and disposition of the individual owls, although the snowy's preference for more open areas again acts as something of a buffer . The snowy may be the one North American owl too formidable for the great horned owl to consider as prey . </P> <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 Northern harriers (Circus hudsonius) 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 was once thought to be strictly monogamous, but recent analysis indicates one male may mate with two females simultaneously, as was discovered for the first time in 2018 in Reno, Nevada . 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>

When do great horned owls get their horns