Boreal Owl

Aegolius funereus

Order STRIGIFORMES - Family STRIGIDAE

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1. Cool Facts
2. Description
3. Similar Species
4. Sound
5. Range
6. Habitat
7. Food
8. Behavior
9. Reproduction
10. Conservation Status
11. Other Names

A small owl of boreal and montane forests, the Boreal Owl is found throughout Alaska and Canada, and across northern Eurasia, as well. It is found in the lower 48 states only in the mountains of the West, in extreme northern Minnesota, and as an occasional winter visitor to the northern states.

Cool Facts

• The female Boreal Owl is much larger than the male. The species shows the most extreme reversed sexual dimorphism of any American owl.

• The Boreal Owl finds its prey by sound. It can locate mice even through vegetation and under snow.

• The ear openings on a Boreal Owl's skull are asymmetrical, with one opening high up on the skull and the other much lower. The different positions of the holes help the owl find exactly where a sound comes from, helping gauge height as well as distance.

• Boreal Owls usually are considered monogamous, with one male mating with one female. Several studies in Europe found that one male may mate with up to three females, and a female occasionally mates with two different males. They found that such multiple mating occurs most frequently when mice numbers are at their highest. (Finding easy prey to feed the young means that less help is needed in raising young owls.) When mice numbers were low, all the owls were monogamous.

Description

• Size: 21-28 cm (8-11 in)
• Wingspan: 55-62 cm (22-24 in)
• Weight: 93-215 g (3.28-7.59 ounces)

• Small owl.
• No ear tufts.
• White face outlined in black.
• Fine spots on top of head.
• Underparts dirty white, streaked with brown.
• Bill yellow.

• Eyes yellow.
• Back brown with large white spots.
• Legs and toes completely feathered.

Sex Differences

Sexes alike in plumage, female larger.

Immature

Upperparts completely dark brown, underparts paler brown. White X on face, made up of eyebrows and white marks below bill.

Similar Species

Northern Saw-whet Owl smaller, with black bill, white streaking on light brown crown, and lacks black outline to face. Juvenile saw-whet with paler and brighter buffy underparts.

Sound

Song a series of low, whistled toots.

»listen to songs of this species

Range

Summer Range

Resident from Alaska eastward across Canada to Labrador, southward to northern New Brunswick and northern Minnesota. Southward in Rocky Mountains to northern New Mexico. Also found across northern Eurasia.

Winter Range

Winters in breeding range, but periodically irrupts further southward to Michigan, southern Ontario, and New York.

Habitat

Lives in boreal forests with spruce, aspen, poplar, birch, and balsam fir. In mountains of West, found in subalpine forests of fir and spruce.

Food

Small mammals, birds, and insects.

Behavior

Foraging

Hunts at night from perches.

Reproduction

Nest Type

Nests in tree cavity, usually old woodpecker hole. Adds no nesting material. Also uses nest boxes.

Egg Description

White.

Clutch Size

Usually 2-6 eggs. Range: 1-19.

Condition at Hatching

Helpless, eyes closed, covered in white down.

Conservation Status

Widespread and common in boreal forest, but reliable population estimates not available. Considered a "sensitive" species in range in United States outside of Alaska. Relies on mature and dead trees for nesting sites, and so is sensitive to clear cutting.

Other Names

Nyctale boréale (French)
Lechuza de Tengmalm (Spanish)
Tengmalm's Owl, Richardson's Owl (English)

Sources used to construct this page:

Hayward, G. D. and P. H. Hayward. 1993. Boreal Owl (Aegolius funereus). In The Birds of North America, No. 63 (A. Poole, and F. Gill, eds.). The Academy of Natural Sciences, Philadelphia, PA, and The American Ornithologists' Union, Washington, D.C.