Boreal owl

The boreal owl was formally described by the Swedish naturalist Carl Linnaeus in 1758 in the tenth edition of his Systema Naturae. Linnaeus placed it with all the other owls in the genus Strix and coined the binomial name Strix funerea. The boreal owl is now placed in the genus Aegolius that was introduced in 1829 by the German naturalist Johann Jakob Kaup with Strix tengmalmi J. F. Gmelin, 1788 (a synonym of A. f. funereus) as the type species. Subspecies Currently, seven subspecies are accepted, Some authors, notably the Ornithological Society of the Middle East, have recommended splitting the Old and New World populations as separate species due to significant differences in vocal behaviour, and genetics; but this has not yet been widely followed. • New World • A. f. richardsoni (Bonaparte, 1838) – Alaska, northern Canada and north United States • Old World • A. f funereus (Linnaeus, 1758) – nominate subspecies, from Scandinavia down south to the Pyrenees and east to the Urals, but not the Caucasus Mountains • A. f. magnus (Buturlin, 1907) – northeast Siberia • A. f. sibiricus (Buturlin, 1910) – southeast and south Siberia • A. f. pallens (Schalow, 1908) – west and central Siberia, south to the central Asian mountains in Kyrgyzstan Fossil history Remains of the boreal owl dating back to the Pleistocene era were found in a cave in southern New Mexico. Bones were found in a pueblo in north-central New Mexico that has been inhabited from around A.D. 1250 to the present. ==Etymology==

The genus name is Latin for a screech owl, the word came from the Ancient Greek aigōlios meaning "a bird of ill omen". The specific epithet funereus is Latin meaning "funereal". ==Description==

The boreal owl is small with a large head and long wings. Both sexes are similar in appearance, though females are larger. Males typically measure in length, with a wingspan of , while females are larger, , with a wingspan of . Females, weighing are heavier than males, which weigh . Adult identification The plumage is brown above, with conspicuous pearly-white spots on the back and wings (giving it its Danish name of perleugle, "pearl owl"), and whitish underparts with rust-coloured streaks. Its large head has yellow eyes and an olive-brown crown with small white droplets and larger central spots. The dull white facial disc is framed with a dark border and white "eyebrows" often described as giving the owl a "surprised" expression. The underparts are cream-white with russet-brown streaks, while the tail has olive-brown feathers with narrow bars. Flight feathers are dark olive-brown with contrasting white spots. The primaries typically have up to five rows of white spots, while the tail has three distinct rows of spots. The beak is light yellow, rather than dark like its relative the northern saw-whet owl. The ears are asymmetrical in multiple bones, which enhances their hunting success. The flight is relatively noiseless and straight. Juvenile identification Juveniles, at about 3 weeks old, have a completely dull, chocolate-brown upperparts and underparts, with a dark brown facial disc bordered by black and white markings near the bill. Upon fledging, their plumage remains similar but with white markings on the neck, scapulars, flight feathers, and tail. They develop a broad white "X" between the eyes and distinct white streaks along the face, with cream-coloured belly and flanks streaked in dark grey-brown. Moults Boreal Owls have two primary moulting phases. The first, post-juvenile moult occurs around the age of two months, between August and September. It only affects the head, body, and wing coverts. The flight feathers, tertials, greater primary coverts, and tail are unaffected. Subsequent moults are also partial, affecting all of the head, body, and wing coverts, as well as the tail, but only a portion of the flight feathers, which are replaced in a specific order each year; the sequence of the primary moult not yet fully understood. Males in Idaho moult from June to October, while females do so from May to October. == Vocal behaviour ==

Calls and related functions can be challenging to interpret because of their nocturnal and hard to locate lifestyle. Starting at one week old, young owls produce a harsh "peep" or "chirp" that softens after fledging. Comprehensive studies in North America have found 8 different types of calls that play an important role in communication, mating, and territorial behaviour: • The Primary Song - loud trill sung by males to attract females and establish territory ==Distribution and habitat==

The boreal owl breeds in dense boreal, subalpine forest as well as mixed woodland. The preferred habitats are old-growth forests as they provide shelter from avian predators and an abundance of prey. Breeding habitats include boreal forests of black and white spruce, ==Behaviour==

Breeding Boreal owls are monogamous and raise a single brood once they reach one year of age. The breeding begins with a lengthy courtship process where males sing for up to 102 days, starting from mid-February to mid-April, depending on environmental factors like prey availability and weather. The nest is usually a hole in a tree often made by a woodpecker, but the birds also readily use nest-boxes. Nesting period last for 28–36 days. The clutch is usually 3-7 eggs which are laid at 2-day intervals. They are glossy white and measure and weigh around . The eggs are incubated only by the female beginning with the second egg and incubation lasts on average 29 days for the first egg and 2.6 days less for the last one. Food and feeding behaviour This small owl eats mainly voles and other mammals (such as mice, chipmunks, other squirrels, gophers, moles, shrews and bats), but also birds as well as small amphibians, Threats Biological resource use - timber harvest Logging activities have a negative impact on prey availability, foraging efficiency and suitable nesting sites. Since the 1990s, significant population declines in northern Europe have been attributed to clear-cutting. Moreover, pesticides from agriculture and forestry effluents are damaging to the species' health. The slow forest succession in spruce-fir ecosystems disrupts the recovery of critical habitat which impacts the species' ability to thrive. Predation Marten species (Martes spp.) and tawny owls (Strix aluco) are the predominant predators of boreal owl owlets and adult females at nest locations, with martens preying on 48% of Norwegian clutches. Other predators include American red squirrels (Tamiasciurus hudsonicus), Cooper's hawk (Astur cooperii), American goshawk (Astur atricapillus), Eurasian goshawk (Astur gentilis) great horned owl (Bubo virginianus) and ural owl (Strix uralensis). Moreover, Eurasian nuthatches (Sitta europaea) have been observed blocking the entrance of nests with mud, occasionally trapping females inside and starving them to death. Mortality Boreal owl mortality rates vary by region and age. In Idaho, adult annual survival rate was 46%, while in Finland, first-year males had a survival rate of 50%, and adult males 67%. Most fledgling males (78%) died before their first breeding attempt. Overall, adult survival ranges from 62% to 72% across studies. Moreover, the average lifespan of breeding males is 3.5 years, and can go up to 11 years. Ringed boreal owls have been known to live up to 16 years. == Conservation status ==

The current population trend is stable with 730,000 - 1,810,000 mature individuals: the species is currently listed under Least Concerned under CITES Appendix II, the EU Birds Directive Appendix I, and Raptors MOU Category 3. Nest boxes are implemented to create suitable nesting sites and ensure reproductive success. The preservation of old-growth forests (with selective tree harvest to allow tree removal while maintaining suitable habitats) and protection of black woodpeckers (Dryocopus martius), that provide nesting cavities, are mandatory for the species' long-term survival. ==References==