A Parliament of Owls

The Boreal Owl operates almost entirely between dusk and dawn, and voles make up the bulk of its diet. Its standard hunting technique is to perch on a low branch and move its head slowly from side to side to pinpoint the movement of a rodent by ear. This species has the most pronounced ear asymmetry of any owl, an indication of the exceptionally powerful hearing with which it finds food in dark forests. Once prey is located, the bird swoops down to secure the prize, sometimes plunging through layers of leaf litter or snow. It may also take other small mammals, including shrews, mice, and moles, and in poor vole years it will more regularly target small birds. Like some other owls, this species may cache food in a tree crevice larder. It has even been observed thawing out frozen prey by crouching on it, as though brooding chicks.

Although hard to see, the Boreal Owl is easily heard; the male’s courtship song is audible for 2 miles (3 km) on a still night. It comprises a series of six to ten “poop” notes, which resemble the call of a hoopoe (Upupa epops) and are repeated with three- to four-second breaks. This song varies between individuals in pitch and speed, so each male in a given area is easily identified. Once a female approaches, the male’s call becomes more stuttering and develops into a long trill as he shows her to a potential nest site. The female’s song is weaker and higher pitched. Both sexes also utter various barks, croaks, and other softer calls. Pair bonding is seasonal, with the male defending a small territory but finding new mates each year. The nest is often an old woodpecker hole, but natural cavities will also do and nest boxes are readily accepted. A female lays three to eight eggs, one day apart, and incubates her clutch for twenty-eight to twenty-nine days, while the male provides food. In good years, a pair may have a second brood.

With an estimated global population of two million, the Boreal Owl is classed as Least Concern. However, numbers are hard to assess and it is declining in some areas. Nesting birds often fall prey to martens, and other predators include the northern goshawk (Accipiter gentilis) and the Tawny Owl (#litres_trial_promo). Nevertheless, habitat loss through deforestation is a much greater threat.

A Boreal Owl peers out from its nest hole beneath the ever-changing night sky.

Burrowing Owls are often seen in pairs or family groups near the entrance to their burrows.

BURROWING OWL

ATHENE CUNICULARIA

APPEARANCE

Small, with round head, long legs, and upright stance; pale yellow eyes, brownish facial disk, white eyebrows and white throat band; under parts pale to brownish, spotted in white and dusky-brown; upper parts and crown brown with whitish streaks and dots; short tail and barred, rounded wings.

SIZE

length 7.5 – 11 in. (19 – 28 cm)

weight 4.9 – 8.5 oz (140 – 240 g)

wingspan 20 – 24 in. (50 – 61 cm)

female slightly larger than male

DISTRIBUTION

In North America, all states west of Mississippi Valley, north to southern Canada, and south into Mexico and Florida; also in South America, Central America, and the Caribbean; birds from northern North America migrate south to Mexico and Central America.

STATUS

Least Concern

IF EVER A BIRD WAS DESTINED to feature in a cartoon strip, it is this charismatic little owl. Typically, it appears from a hole in the ground, stands tall on stilt-like legs, bobs its head up and down, and fixes you with a furious glare. Small wonder that the Burrowing Owl continually pops up, so to speak, in children’s fiction, recently as a band of Mexican Mariachi musicians in the animated movie Rango (2011).

This is the most terrestrial of the world’s owls: it not only spends much of its time on the ground, but also, as the name suggests, nests beneath it. Although capable of digging its own burrow, this owl generally reappropriates the burrow systems of ground-dwelling mammals, such as prairie dogs (Cynomys). The two are often seen in close proximity and inhabit the same terrain: open grasslands, from the prairies of North America to the pampas of South America. Other favored habitats range from semidesert to pinyon and ponderosa pine scrub, and this owl will happily take to farmland and other human landscapes, too, including golf courses and airports, if conditions are suitable.

The Burrowing Owl is one of the most widely distributed owls in the Americas. However, it avoids mountains and forest. In South America, for example, it is found discontinuously in all suitable habitat as far south as Tierra del Fuego, but is absent from the Amazon Basin and the high Andes. Birds toward the north of the North American range are migratory, but the South American population is largely sedentary.

This species was once assigned its own genus, Speotyto. Today, most taxonomists group it within Athene, along with Eurasia’s Little Owl (#litres_trial_promo), which it closely resembles. The fragmented distribution has produced up to twenty-two subspecies, with the nominate race, A. c. cunicularia, found on the eastern side of South America. These vary in markings, but the Burrowing Owl’s distinctive habits and posture—small, round head and long-legged silhouette atop an anthill or fence post—mean that confusion with other owls is unlikely. In fact, it is one of the easier owls to observe up close; it is both diurnal and reasonably approachable, especially where it is used to human disturbance. A good view reveals pale yellow eyes set in a brownish facial disk. The strong white throat band stands out above a brownish upper breast, which is spotted in white to differing degrees according to subspecies. The tarsi are long and white, the tail is short, and the heavily barred wings appear broad and rounded in flight. Males are generally lighter in color, especially toward the end of the breeding season, when their guard duties outside the burrow expose their plumage to the bleaching of the sun.

The Burrowing Owl is seldom seen far from its burrow, and often perches at the entrance or on a nearby perch. When alarmed it will bob up and down excitedly, and if threatened it will fly away low, with irregular, jerky wingbeats between long glides. Although visible throughout the day, the bird becomes most active at dusk. Its prey changes with season and location, but the staple diet in most areas is large arthropods, including beetles, grasshoppers, and scorpions. However, this owl will also turn to small vertebrates, from reptiles and amphibians to small mammals, as well as birds up to the size of the eared dove (Zenaida auriculata), which is its equivalent. Birds in different areas specialize in a particular food type: in southern Brazil, for example, the delicate vesper mouse (Calomys tener) is a favorite. The usual hunting technique is to watch for prey, then glide silently toward it and snatch it from the ground with talons. However, the Burrowing Owl is a versatile little predator and will also chase insects on foot or hawk them in midair. When feeding young, it may hunt around the clock.

In the northern hemisphere, courtship starts in March and April. Generally, this species forms monogamous pairs, although polygyny—one male mating with and providing for two or more females in separate burrows—is occasionally recorded. Activity starts with the male’s distinctive two-syllable call, a hollow “cu-cuhooh.” This song varies according to individual and mood. The female’s call is similar but higher, and both sexes have a repertoire of harsh and curious calls. The male backs up his vocal performance with a choreographed courtship display, in which he coos, bows, and scratches the ground, flashing his prominent white throat and eyebrows. He may also rise in a brief hovering display flight, hanging above the female, then flying in a circle around her.

A pair will return to the same nesting burrow, or one close by, for many years in succession. Once settled, the female lines the burrow with dry material, including cattle dung. Indeed, the pair will often deposit dung outside the burrow entrance: once thought to be a means of repelling predators, this is now believed to encourage dung beetles and other insects on which the owls can feed. The female lays six to nine eggs (a maximum of twelve), one day apart, which she incubates for twenty-eight to thirty days. The male, meanwhile, provides food and aggressively defends the small area around the burrow.

In productive habitat, the Burrowing Owl may form loose colonies. This enables it to cooperate in sounding the alarm and warding off predators. Another ingenious defense system is deployed by the young chicks in the burrow: if disturbed, they make a harsh alarm call that sounds uncannily like the warning rattle of a rattlesnake. This is a prime example of Batesian mimicry, in which a vulnerable animal imitates a more dangerous one in order to deceive a potential predator. And this species certainly has many predators, from larger owls and other raptors to badgers, skunks, armadillos, and even domestic cats and dogs.

Globally, the Burrowing Owl is classed as Least Concern, with an estimated population of two million individuals. However, its wide distribution belies the fact that it is declining in many areas. Today, it is endangered in Canada, threatened in Mexico, and of special concern in Florida. Among the threats it faces are the loss of habitat to agricultural intensification, pesticides, and control programs for prairie dogs. Conservationists try to relocate Burrowing Owls whose burrows are threatened by a development project by enticing them to new burrows and perches constructed on safe alternative quarters nearby.

Burrowing Owls often find a home in human environments.

A Burrowing Owl drives an American Badger away from its nesting burrow.

Frogs feature among a wide variety of prey for this species.

The Great Horned Owl held an iconic status among the native peoples of North America.

GREAT HORNED OWL

BUBO VIRGINIANUS

APPEARANCE

Medium-large to large owl with prominent ear tufts; plumage variable across its range; rusty-brown to ocher facial disk, with blackish rim, whitish eyebrows, yellow-orange eyes, and white throat; upper parts warm brownish-buff, patterned in gray, black, and white; crown, tail, and flight feathers strongly barred; under parts brownish buff, with blackish blotches and crossbars and sometimes a white stripe down the center.

SIZE

length 17 – 25 in. (43 – 64 cm)

weight 2.6 – 5.5 lb (1.2 – 2.5 kg)

wingspan 3 – 5 ft (91– 153 cm)

DISTRIBUTION

All of North America south of the northern treeline; Central America into northern South America, from coastal Venezuela to Peru; discontinuous population south of the Amazon Basin in southern and eastern Brazil and Argentina.

STATUS

Least Concern

THE SIZE, FEROCITY, AND BEAUTY of this impressive owl made it a subject of veneration among many Native American peoples. In the southwest, the Pima believed that it was a reincarnation of slain warriors who fly about by night, whereas the Arikara of the Great Plains conducted mystical initiation ceremonies, wearing facial masks adorned with its wing and tail feathers. For others, it was a spiritual intermediary in matters of love or crop fertility, and the Hopi used its feathers in a winter solstice ceremony in the hope of summoning the heat of summer. Today, it remains North America’s best-known owl, and it is the provincial bird of Alberta.

Within North America, the Great Horned Owl is unmistakable. Resembling a slightly smaller version of the Eurasian Eagle Owl (#litres_trial_promo), it is a typical member of the Bubo genus, with a large powerful body, broad wings, and prominent ear tufts. Its only rival for size on the continent is the slightly heavier Snowy Owl (#ulink_099ac609-f10a-5029-b8d0-5441af15b02a) and, like its Arctic cousin, it is an apex predator wherever it occurs. First described to science by early settlers in the Virginia colonies, hence its scientific name virginianus, it is also known as the “hoot owl” and “winged tiger”—the latter a reference to its strong, stripe-like barring. In general, this owl has a rusty-brown to ocher facial disk, with a prominent rim and eyebrows that accentuate the stern expression of the bright yellow-orange eyes. Its ear tufts are long and tousled, and held erect when alarmed or roosting. Upper parts are a warm brownish-buff, finely marked and mottled in gray, black, and white; under parts are brownish-buff, paler toward the belly, with strong blackish blotches and crossbars. The white throat is especially prominent when inflated during the bird’s territorial calling, and it may continue as a whitish stripe down the center of the breast.

The Great Horned Owl occurs across the entirety of North America and down through Central America into northern South America. In southern and western South America, it is replaced by the similar but slightly smaller and paler Magellanic Horned Owl (Bubo magellanicus), with which it was once thought to be conspecific until DNA research proved otherwise. Taxonomists recognize up to twenty subspecies, which differ in size and markings. Birds in forested regions tend to be darker and those in northern regions larger, thereby following Bergman’s rule, which states that individuals of any species tend to be larger in the colder parts of its range, because a higher body mass to surface area ratio helps to preserve heat. Northernmost populations may migrate south in winter, depending on weather conditions.

This species has a very wide habitat tolerance, found from dense forests to desert fringes, from open plains to city parks, and ranging up to 14,700 feet (4,500 m) in the Andes. Wherever it occurs, however, the Great Horned Owl requires mature trees for roosting and nesting and open ground or clearings in which to hunt. It generally becomes active around dusk and roosts by day, typically against a tree trunk, where its camouflage patterning is highly effective. In some regions, it may be out and about in the early morning or late afternoon.

The Great Horned Owl takes a variety of prey, which is one explanation for its success. Small to medium-sized mammals are at the top of the menu: typically, rabbits and hares, but also everything from small rodents to bats, squirrels, armadillos, raccoons, muskrats, porcupines, and domestic cats. Birds are also taken and range from crows, pigeons, and woodpeckers to grouse, herons, turkeys, and raptors, including all other North American owls except the Snowy Owl. Its standard hunting technique is to watch from an elevated perch, then swoop down with wings folded, before swinging its lethal talons forward to grab the prey. It may also hunt by quartering the ground like a Short-eared Owl (#litres_trial_promo). Such is the power of this owl—with feet that can exert 300 pounds of pressure per square inch (136 kg per 6.5 sq cm), about five times that of a human hand—that it can kill prey weighing up to three times its own weight. It is also highly versatile and has been known to wade into water to capture fish or even walk into an open hencoop to seize a chicken. Observations suggest that for hunting it relies more on eyesight than hearing, and indeed its eyes are almost as big as those of a human.

The Great Horned Owl is largely monogamous, with a pairdefending the same breeding territory for up to eight years. Outside the breeding season, however, it is solitary and does not get together with its mate until late winter to renew its bond. The male’s courtship song is a sequence of deep mellow hoots, with an emphasis on the central one: “hoo hoo HOOO hoo hoo.” He may call from dusk to midnight, and again just before dawn. The female responds with a similar but higher-pitched call. When the pair are close, the male will perform a bowing display, with wings drooped and white throat fluffed out. Among other noises in this owl’s broad vocal repertoire are various grunts, meows, and shrieks, and a growling “krooo-oo” given when attacking intruders.

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.