Boreal Owl - Aegolius funereus

Also known as Tengmalm's Owl

Male territorial song		© Brinzal
Chick calling		© Brinzal

The Boreal, or Tengmalm's Owl was first classified in 1758 by Carolus Linnaeus (1707-1778), the Swedish naturalist, who developed binomial nomenclature to classify and organise plants and animals. "Funereus" comes from the Latin word for funeral. In North America, where it is known as the Boreal Owl, it was named after the Greek god of the north wind, Boreas. In other parts of the world, it is known as Tengmalms Owl. Other names for this Owl are Richardson's Owl, Sparrow Owl, Partridge-haw and Pearl Owl (Finland).

Description: Colouration varies widely between individuals, with some having reddish-brown hues, while others are more greyish.
The facial disc is whitish, surrounded by a dark rim with small white spots. There is a small dark portion between the eyes and the base of the bill. Eyes are pale to bright yellow, and the bill is yellowish horn.
Upper parts are dark brown with bold white spotting. Underparts are off-white, with broad streaks of darkish brown, denser on the breast and trailing off at the lower belly.
The tail is short and brown, with 4-5 white cross-bars. The legs and feet are covered with white feathers. Claws are darkish horn to blackish brown, and have very sharp black tips.

Size: Length: 20-30cm (7.9-11.8")
Wing length (one wing): Females 164-185mm (6.5-7.3")  Males 158-178mm (6.2-7")
Weight: Females 126-194g (4.5-6.8oz)  Males 90-113g (3.2-4oz)

Habits: A nocturnal Owl, also unsociable. Adult males are territorial, however, territories are small. Males will sing intensively only as long as they are unmated. Flight is straight and noisless, with soft wingbeats.

Voice: The most common call is the territorial song of the male, which varies widely from individual to individual. It is a series of "Poop" notes followed by a 3-4 second break, then another series. The individual variation is in the number of notes and the pitch and speed at which the notes are uttered.
When the female approaches the singing male, the notes become more "stuttering". This usually leads into a trill of up to 350 rapid notes, which is sung from potential nest sites to show the female.
The male will emit a low "Wood" or "Wood-whoohd" to contact a breeding female. To show aggression he can deliver a whip-like "zjuck" sound.
The female's call is infrequently heard, and similar to the male's, but fainter, higher pitched and not as clear. An aggressive female may utter a sharp "Jack" as well as hoarse "oohwack" and croaking sounds "kraihk, kwahk".
When the male announces his arrival with trills or "wood" calls, the female will respond from the nest hole with a high pitched "seeh", sometimes with a verse of suppressed song. Her contact call is a mewing, hoarse "zuihd".

Hunting & Food: Boreal Owls usually hunt by perching on low branches or tree trunks. The Owl will scan the ground by moving its head slowly from side to side, listening for movement of potential prey, as they hunt primarily using their excellent, directional hearing. When a victim is located, the Owl will swoop on it from the perch.
Prey Items are mainly small rodents, especially Voles. They also eat lemmings, shrews, mice, and moles. They occasionally take small birds, squirrels, bats, frogs and beetles.
Pellets are thick, grey and about 22x12mm (0.9x0.5") and found mostly around the daytime roost.

Breeding: The Boreal or Tengmalm's Owl nests mainly in old woodpecker cavities, but may also use natural cavities. They will take readily to artificial nest boxes.

Males begin searching for nest holes in late Winter. Prey items are often deposited into the hole, after which, the male will sing from a perch. If an interested female approaches, the male will fly to the cavity and utters a stuttering or trilling song. The female may then inspect the nest hole, and if she accepts it, will stay. The male brings her food while she is in the hole.
Several days later, the female lays 3-8 white eggs which are laid a day apart. Incubation begins with the first or second egg laid, and lasts 28-29 days. The female does all incubation and the male brings food to the nest. The chicks hatch a day apart, and their eyes open after 10 days. They leave the nest at about 30-32 days, and are looked after by the parents for 4-6 weeks. They are mature at about 9 months.

The Tengmalm's / Boreal Owl is usually single-brooded, but will sometimes try to produce 2 broods. Breeding success is fairly high. Desertion or predation of eggs and young are the primary causes of nest failure. Unlike most other owls, pair bonding is only seasonal.

Mortality: These Owls can live for at least 7-8 years. Incubating females are sometimes killed by Pine Martens. They are also preyed upon by larger raptors, such as other owls and Goshawks.

Habitat: Preferred habitat varies throughout its range but includes mainly old-growth forests with woodpecker cavities for nesting. They inhabit a range of forests from pure coniferous to pure deciduous forests. Southern populations tend to occur in high subalpine forests. Hunting habitat includes forest meadows and open forests. When roosting they need dense conifers where they roost 5 to 6 meters (16 to 20 feet) up.

Distribution: Roughly follows the northern forest belt. Also occurs locally in Europe. In North America, the distribution is generally confined to the forest areas of the Rocky Mountains. To the east of the Rockies they occur as far south as New Mexico, and to the west they occur in forests from Alaska to Oregon.

Distribution of Aegolius funereus

Status: Generally uncommon to rare. Endangered in some areas. Locally may be common.

Original Description: Linnaeus, Carolis. 1758. Systema Naturae (Syst. Nat.) ed. 10: p 93.

Subspecies: A. f. funereus, A. f. beickianus, A. f. caucasicus, A. f. magnus, A. f. pallens, A. f. richardsoni, A. f. sibiricus

References:

Page Information:

Page compiled by Deane P. Lewis.

OwlPages.com Owl Species ID: 230.010.000 - Page last updated 2005-04-25