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. 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, 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