The nest is usually an old abandoned stick nest of another bird, typically a crow, raptor, or heron. Tree hollows, rocky caves, and abandoned buildings are sometimes also used. The female lays two to four eggs, which she incubates for twenty-six to thirty-five days. The male roosts nearby by day and hunts for his mate and young at night. At six to seven weeks, the young start roaming outside on nearby branches, and by nine to ten weeks they can fly. A pair of owls is extremely aggressive while rearing young and will attack intruders until they are killed or driven away. This species has a particularly fractious relationship with the red-tailed hawk (Buteo jamaicensis), whose breeding territory it shares.
Although the Great Horned Owl seldom lives more than thirteen years in the wild, it has topped thirty in captivity. It has few natural threats, although occasionally falls victim to the golden eagle (Aquila chrysaetos). Of more concern are human threats, which, in addition to the ongoing loss of habitat to development and agricultural intensification, include collisions with road traffic and power lines. Nonetheless, with a population estimated to be at least five million individuals, this species is classified as Least Concern.
The Great Horned Owl is a species of all terrain, from the cold forests in the north of North America to the deserts in the south.
Three nestlings peer out from their spiny cactus citadel.
An adult Great Horned Owl shows the long wings typical of Bubo owls.
A female Great Horned Owl at its nest in a tree cavity; intruders are repelled fiercely.
A Western Screech Owl, like all screech owls, is camouflaged to resemble the trees in which it nests and roosts.
WESTERN SCREECH OWL
MEGASCOPS KENNICOTTII
APPEARANCE
Small; pale brown facial disk with dark edges and faint eyebrows over yellow eyes and a yellowish bill; crown and upper parts gray-brown and heavily streaked, with white scapular line on shoulders; under parts pale, with blackish streaks and irregular cross-barring; flight feathers and tail heavily barred; a rare brown color morph occurs in some northern areas.
SIZE
length 8.7 in. (22 cm) ave
weight 3.1 – 7.8 oz (88 – 220 g)
wingspan 22 in. (55 cm)
females slightly larger than males
DISTRIBUTION
Western North America, from Alaska in the far north, south to central Mexico and east to Western Texas.
STATUS
Least Concern
“SCREECH” IS NOT A PARTICULARLY APT NAME for this diminutive owl. It can certainly produce a variety of harsh noises, but the call for which it is best known is the male’s distinctive territorial song: a series of whistled notes all uttered at the same pitch and accelerating with the rhythm of a bouncing ball. This repetitive refrain can be heard after dark up the length of western North America. It carries for more than a mile on still nights, providing a nocturnal sound track to landscapes as diverse as the humid northwest forests of towering Douglas firs and the stands of saguaro cactus on the edge of the Arizona desert. Rival males contest their territorial claims, each hoping for a female’s answer.
This species is one of several very similar owls in the Megascops genus. It was once thought to be conspecific with the Eastern Screech Owl (Megascops asio), which occupies a corresponding ecological niche in the eastern half of the continent, but the two have completely different songs—voice is the most reliable way to separate species in this genus—and DNA studies have confirmed that they are indeed different species. In the few places where their ranges overlap, such as the Pecos River in Texas, they are not known to interbreed.
The Megascops screech owls comprise up to twenty-nine species and are the New World equivalent of the Old World scops owls (Otus). Some six to eight million years ago, the two groups diverged from a common ancestor, and it was only in the late twentieth century that taxonomists assigned each its own genus. Certainly, the Western Screech Owl looks very similar to the Common Scops Owl and other Otus species. It is roughly the same size, with a large round head, short tail, distinct ear tufts, and cryptic plumage that provides effective camouflage at its daytime roost. Taxonomists recognize nine subspecies, with the nominate race M. k. kennicottii found from Alaska to northern California. Across most of its range, this bird is a permanent resident; only at the northernmost limits do some undertake southbound winter migrations.
The diverse habitats favored by the Western Screech Owl comprise a mixture of woodland, with abundant nesting cavities and roost sites, and open country, in which it can hunt. Consequently, it tends to occur in highest densities at forest edges, clearings, and alongside rivers. Forest types vary from western hemlock, western red cedar, and Sitka spruce in the northwest, to deciduous woodland, pinyon pine, and cacti stands in the southwest. This species avoids dense forest, partly because here it runs a greater risk of encountering the Great Horned Owl and Barred Owl, which both pose a significant threat. It has, however, shown an increasing capacity to adapt to gardens and suburban habitats, which serve well when prime wild habitat is lost elsewhere.
The Western Screech Owl is a nocturnal bird, seldom active by day. It roosts in tree cavities or in dense foliage near the tree trunk, where it freezes when disturbed in an attempt to blend into the bark. About half an hour after sunset, it sets out hunting, at which point it is often seen moving between trees. It flies directly—with glides interspersed between bursts of fast, soft wingbeats—and appears rather front-heavy, with its short tail and large head tucked in. This bird’s standard hunting technique is to watch for prey from a high perch—often on a forest edge or beside wetlands—and then, having spotted a target, to swoop down and grab it, delivering the mortal blow with its sturdy little bill. Prey varies from deer mice (Peromyscus) and other small rodents to large insects and small birds, depending on local abundance. This agile owl is also able to capture prey on the wing, including insects, bats, and flying squirrels. It has even been known to snatch small trout from a pool, scavenge from a roadkill possum, and attack domestic ducks that are at least twice as big as itself.
The Western Screech Owl generally mates for life, but an individual will take a new partner if it loses its mate. Adults remain near their breeding territory and may use the same nest site for many years. Courtship starts in late winter or early spring, when males sing their bouncing-ball refrain in order to reestablish territorial boundaries. Once mates have renewed contact, the male’s call changes to a high double trill. Male and female duet as they approach one another through the woods. The male performs a dancing display along a branch, and the two birds nibble bills and preen one another as they renew their bonds and he shows her to a suitable nest site. They may also make discreet barking and chuckling calls, as well as a softer “coo-roo” in greeting. The nest site is a tree hole, usually one excavated by a woodpecker. It is generally located around 16 to 20 feet (5 – 6 m) off the ground in a large deciduous tree, such as an oak or sycamore, but sizable fir trees and junipers will also do, as will cacti in the southwest. One