Aegolius funereus

Aegolius_funereus can be found in subalpine and boreal forests across the northern hemisphere, including the Neartic and Palearctic regions of the globe. Its range generally follows the northern forest belt.

In North America, where they are known as boreal owls, the range extends from Alaska to eastern Canada.

In Eurasia A._funereus is called Tengmalm’s owl. In Europe they are found mostly in Scandinavia, though there are several scattered populations also found in subalpine forests in the central mountain regions. The range of Tengmalm’s owls extends eastward from Scandinavia, stretching across virtually all of northern Siberia, as they inhabit the taiga lowlands. Their range dips south as it approaches the Pacific Ocean, occurring throughout forested mountains north of the Korean Peninsula.

Biogeographic Regions: nearctic (Native ); palearctic (Native )

Other Geographic Terms: holarctic

Aegolius funereus can be found in subalpine and boreal forests across the northern hemisphere, including the Neartic and Palearctic regions of the globe. Its range generally follows the northern forest belt.

In North America, where they are known as boreal owls, the range extends from Alaska to eastern Canada.

In Eurasia A. funereus is called Tengmalm’s owl. In Europe they are found mostly in Scandinavia, though there are several scattered populations also found in subalpine forests in the central mountain regions. The range of Tengmalm’s owls extends eastward from Scandinavia, stretching across virtually all of northern Siberia, as they inhabit the taiga lowlands. Their range dips south as it approaches the Pacific Ocean, occurring throughout forested mountains north of the Korean Peninsula.

Biogeographic Regions: nearctic (Native ); palearctic (Native )

Other Geographic Terms: holarctic

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (20,000 to >2,500,000 square km (about 8000 to >1,000,000 square miles)) Breeds in North America from treeline in central Alaska east to Newfoundland; south central Oregon in the Cascade and Blue Mountains, and in the Rocky Mountains south through Washington, Idaho, Montana, Wyoming, and Colorado to northern New Mexico; then east through central Saskatchewan, southern Manitoba, northern Minnesota, southern Quebec and Ontario. Breeds in Eurasia from treeline in northern Scandanavia, Russia, and Siberia, south in the mountians to southern Europe, the western Himalayas, and western China (AOU 1983, Hayward and Hayward 1993). Winters mainly in hte breeding range, however it may move south in the eastern U.S. and Europe during eruption years (A.O.U. 1983, Hayward and Hayward 1993).

Aegolius_funereus individuals are small owls with large, rectangular heads and long wings. Males are typically between 21 and 25 cm in length, while females are slightly larger, being between 25 and 28 cm. Like most owls, they have an obvious, light colored facial disc. The head is covered in brown and black mottled feathers. The bill is whitish-yellow, in contrast to the black bill of the northern saw-whet owl. The underparts are white, while the back and wings are predominantly dark brown with lighter spots. The legs are covered in white feathers to the claws. Aegolius_funereus is unique from all other owls in that, when the tail is closely folded, there are 3 rows of white spots visible on the dorsal surface. Females are larger than males, weighing 132 to 215 grams, while males weight from 93 to 139 grams. Wing spans are between 55 and 58 cm in males and between 59 and 62 cm in females.

Young are similar in appearance to adults, with more muted colors.

Range mass: 93 to 215 g.

Range length: 21 to 28 cm.

Range wingspan: 55 to 62 cm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: female larger

Aegolius funereus individuals are small owls with large, rectangular heads and long wings. Males are typically between 21 and 25 cm in length, while females are slightly larger, being between 25 and 28 cm. Like most owls, they have an obvious, light colored facial disc. The head is covered in brown and black mottled feathers. The bill is whitish-yellow, in contrast to the black bill of the northern saw-whet owl. The underparts are white, while the back and wings are predominantly dark brown with lighter spots. The legs are covered in white feathers to the claws. Aegolius funereus is unique from all other owls in that, when the tail is closely folded, there are 3 rows of white spots visible on the dorsal surface. Females are larger than males, weighing 132 to 215 grams, while males weight from 93 to 139 grams. Wing spans are between 55 and 58 cm in males and between 59 and 62 cm in females.

Young are similar in appearance to adults, with more muted colors.

Range mass: 93 to 215 g.

Range length: 21 to 28 cm.

Range wingspan: 55 to 62 cm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: female larger

Length: 25 cm

Weight: 167 grams

Aegolius_funereus occur almost exclusively in coniferous forests. However, they are also found in areas of deciduous forest. Dominant tree species in these forests include Engelmann spruce, black spruce, white spruce, aspen, poplar, birch, and balsam fir. They are usually found in dense forests, they seem to avoid areas that are more exposed.

In North America, boreal owls are found from 1580 m to over 3200 m. They occur as low as 1100 m in Central Europe and as high as 2000 m in Siberia. However, during extreme weather, Tengmalm’s owls have been observed as low as 400 m.

Range elevation: 400 to >3200 m.

Habitat Regions: temperate ; terrestrial

Terrestrial Biomes: taiga ; forest

Systems

• Terrestrial

Aegolius funereus occur almost exclusively in coniferous forests. However, they are also found in areas of deciduous forest. Dominant tree species in these forests include Engelmann spruce, black spruce, white spruce, aspen, poplar, birch, and balsam fir. They are usually found in dense forests, they seem to avoid areas that are more exposed.

In North America, boreal owls are found from 1580 m to over 3200 m. They occur as low as 1100 m in Central Europe and as high as 2000 m in Siberia. However, during extreme weather, Tengmalm’s owls have been observed as low as 400 m.

Range elevation: 400 to >3200 m.

Habitat Regions: temperate ; terrestrial

Terrestrial Biomes: taiga ; forest

Comments: Dense coniferous forest, mixed forest, thickets of alder, aspen, or stunted spruce, most commonly in proximity to open grassy situations (AOU 1983); muskeg bogs. In the Rockies, occurs generally in mature, multilayered spruce-fir forest. Roosts in dense cover by day, in cool microsites in summer; frequently changes roosting site.

Nests in tree hole, natural cavity or old woodpecker hole; sometimes in artificial nest boxes (Harrison 1978). Nest site may be used in consecutive years. Three nest holes in Colorado were 78-100 mm in diameter (see Johnsgard 1988). A nest in Montana was in a dead broken-topped subalpine fir; the cavity opening measured 73 mm X 64 mm (Holt and Ermatinger 1989).

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Periodic large-scale southward irruptions in North America, frequently in synchrony with similar movements of great gray and hawk-owl. Tends to occur at higher elevations in summer; may move to lower elevation for winter. In Colorado, some males remain at high elevations all year; others wander extensively (Johnsgard 1988).

Boreal owls are carnivorous. They feed primarily on small mammals, such as voles, mice, chipmunks, and squirrels. In North America, they have been observed preying on red-backed voles (Clethrionomys_gapperi), heather voles (Phenacomys_intermedius), jumping mice (Zapus), northern pocket gophers (Thomomys_talpoides, and northern flying squirrels (Glaucomys_sabrinus). Boreal owls have also been hunting insects and small birds, such as dark-eyed juncos (Junco_hyemalis), American robin (Turdus_migratorius), and common redpolls (Carduelis_flammea). Females may prefer larger, mammalian prey and males may specialize on hunting smaller mammals and birds. During the winter and breeding season boreal owls cache food in rock crevices or tree branches.

When hunting, boreal owls sit on a perch and wait for prey to scamper into sight. They usually select a perch that is bare below, but provides good cover overhead, so that it is more difficult for predators to spot them. Once they have spotted prey, they descend slowly, grasp the prey with their claws, bracing themselves against the ground for leverage. They kill prey with a quick bite to the head or neck. Boreal owls typically eat prey on a perch.

Animal Foods: birds; mammals; insects

Foraging Behavior: stores or caches food

Boreal owls are carnivorous. They feed primarily on small mammals, such as voles, mice, chipmunks, and squirrels. In North America, they have been observed preying on red-backed voles (Myodes gapperi), heather voles (Phenacomys intermedius), jumping mice (Zapus), northern pocket gophers (Thomomys talpoides, and northern flying squirrels (Glaucomys sabrinus). Boreal owls have also been hunting insects and small birds, such as dark-eyed juncos (Junco hyemalis), American robin (Turdus migratorius), and common redpolls (Carduelis flammea). Females may prefer larger, mammalian prey and males may specialize on hunting smaller mammals and birds. During the winter and breeding season boreal owls cache food in rock crevices or tree branches.

When hunting, boreal owls sit on a perch and wait for prey to scamper into sight. They usually select a perch that is bare below, but provides good cover overhead, so that it is more difficult for predators to spot them. Once they have spotted prey, they descend slowly, grasp the prey with their claws, bracing themselves against the ground for leverage. They kill prey with a quick bite to the head or neck. Boreal owls typically eat prey on a perch.

Animal Foods: birds; mammals; insects

Foraging Behavior: stores or caches food

Primary Diet: carnivore (Eats terrestrial vertebrates)

Comments: Eats mainly small mammals (often MICROTUS and CLETHRIONOMYS, also SOREX and PEROMYSCUS); also sometimes birds and insects (Bent 1938, Ryder et al. 1987, Hayward 1989).

Boreal owls are thought to be one of the most important avian predators of small mammals, such as voles and mice, throughout their range. More than 90% of their diet comes from this source. They are also, as noted above, a prey animal for several other species.

The primary predators of adult and fledgling boreal owls are other owls and hawks. Included in these are: Accipiter_cooperi (Cooper's hawks), A._gentiles (northern goshawks), Buteo_virginianus (great horned owls), Strix_uralensis (Ural owls), and Strix_aluco (tawny owls). All of these predators hunt boreal owls from the air. When they sense a predator nearby, boreal owls will shrink away into a concealment position, remaining motionless and as small as possible to prevent from being seen.

Martens (Martes) are the primary predators of eggs, owlets, and adult females in the nest. Red squirrels (Tamiasciurus_hudsonicus) are also probable egg predators.

Known Predators:

• Cooper's hawks (Accipiter_cooperi)
• northern goshawk (Accipiter_gentilis)
• great horned owls (Bubo_virginianus)
• Ural owls (Strix_uralensis)
• tawny owls (Strix_aluco)
• martens (Martes)
• red squirrels (Tamiasciurus_hudsonicus)

Anti-predator Adaptations: cryptic

Boreal owls are thought to be one of the most important avian predators of small mammals, such as voles and mice, throughout their range. More than 90% of their diet comes from this source. They are also, as noted above, a prey animal for several other species.

The primary predators of adult and fledgling boreal owls are other owls and hawks. Included in these are: Accipiter cooperi (Cooper's hawks), A. gentiles (northern goshawks), Buteo virginianus (great horned owls), Strix uralensis (Ural owls), and Strix aluco (tawny owls). All of these predators hunt boreal owls from the air. When they sense a predator nearby, boreal owls will shrink away into a concealment position, remaining motionless and as small as possible to prevent from being seen.

Martens (Martes) are the primary predators of eggs, owlets, and adult females in the nest. Red squirrels (Tamiasciurus hudsonicus) are also probable egg predators.

Known Predators:

• Cooper's hawks (Accipiter cooperi)
• northern goshawk (Accipiter gentilis)
• great horned owls (Bubo virginianus)
• Ural owls (Strix uralensis)
• tawny owls (Strix aluco)
• martens (Martes)
• red squirrels (Tamiasciurus hudsonicus)

Anti-predator Adaptations: cryptic

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 81 to >300

10,000 to >1,000,000 individuals

Comments: Population "large" in Canada (1995 COEWIC unpubl. report).

In Idaho, annual home range averaged 1528 ha (522-4119 ha); home ranges overlapped extensively; range was larger in winter than in summer; center of winter and summer ranges were separated by average of 2333 m (Hayward et al. 1987). Defends nest site only.

Boreal owls are solitary animals, and do not communicate often with other boreal owls except during the breeding season. In order to attract a mate, a male will sing and also making flying passes past females. After leaving the nest, young will call out to their parents with a begging call when they are hungry. Other calls include a warning call used by both sexes as well as a call used by the male to let the female know he has brought food to the nest. Boreal owls will also snap their bill together as a warning when they feel threatened.

Boreal owls perceive their environment visually, acoustically, and chemically. They have keen eyesight, especially in the dark, and can detect prey by prey-generated sounds. Boreal owls, like most owls, have an asymmetrical external ear structure that makes it possible for them to precisely locate prey using only prey-generated sounds. They can hunt for prey completely hidden under snow cover.

Communication Channels: visual ; acoustic

Boreal owls are solitary animals, and do not communicate often with other boreal owls except during the breeding season. In order to attract a mate, a male will sing and also making flying passes past females. After leaving the nest, young will call out to their parents with a begging call when they are hungry. Other calls include a warning call used by both sexes as well as a call used by the male to let the female know he has brought food to the nest. Boreal owls will also snap their bill together as a warning when they feel threatened.

Boreal owls perceive their environment visually, acoustically, and chemically. They have keen eyesight, especially in the dark, and can detect prey by prey-generated sounds. Boreal owls, like most owls, have an asymmetrical external ear structure that makes it possible for them to precisely locate prey using only prey-generated sounds. They can hunt for prey completely hidden under snow cover.

Communication Channels: visual ; acoustic

Comments: May forage day or night; most hunting occurs at night (Hayward 1989).

The longest known lifespan for a boreal owl is 16 years, from several banded individuals in various studies. In Finland, a study was done to determine the survival rate of A._funereus. Only 50% of first year males survived, while 67% of adult males survived annually. Other studies have put adult survival at 72% and 62% respectively. Yet another study determined that 78% of fledgling males died before they reached sexual maturity.

Range lifespan
Status: wild: 16 (high) years.

Average lifespan
Status: wild: 3.4 years.

Average lifespan
Sex: male
Status: wild: 11.0 years.

The longest known lifespan for a boreal owl is 16 years, from several banded individuals in various studies. In Finland, a study was done to determine the survival rate of A. funereus. Only 50% of first year males survived, while 67% of adult males survived annually. Other studies have put adult survival at 72% and 62% respectively. Yet another study determined that 78% of fledgling males died before they reached sexual maturity.

Range lifespan
Status: wild: 16 (high) years.

Average lifespan
Status: wild: 3.4 years.

Average lifespan
Sex: male
Status: wild: 11.0 years.

Maximum longevity: 15.9 years

Aegolius_funereus is primarily monogamous. However, there have been documented cases of both bigyny (one male with two mates) and biandry (one female producing two clutches by two different mates). These cases have been observed only in Eurasia, and only when food is extremely plentiful. Males don't defend large foraging territories, but rather nest sites (old woodpecker holes), which are often in short supply. Fights between males have not been observed, and it appears that they compete for females through song and flight. Males will fly between perches near females, and sing a courtship song to attract female interest. If a female is interested, she will inspect the nest and, if she accepts it, she will simply stay there. The courtship period might last anywhere from 2 to 6 weeks for individual owls and from 1 to 4 months for the population as a whole.

Mating System: monogamous

Breeding season is variable, but takes place most commonly from March to June. Clutch size varies with food availability, but is typically around 4 or 5. Eggs are laid once every two days and brooding begins with the first egg, so hatching is asynchronous. Incubation is typically 28 days long. Young fledge about 30 to 31 days after hatching. The young are cared for by their parents for about a 6 weeks after fledging before setting out on their own. They become sexually mature in their first year, at around nine months old.

Breeding interval: Boreal owls typically breed once yearly. If food is plentiful then multiple clutches may occur.

Breeding season: Breeding season is highly variable, but is typically from the end of February to as late as July.

Range eggs per season: 2 to 7.

Average eggs per season: 5.

Range time to hatching: 25 to 32 days.

Range fledging age: 28 to 36 days.

Range time to independence: 6 to 7 weeks.

Range age at sexual or reproductive maturity (female): 9 to 9 months.

Range age at sexual or reproductive maturity (male): 9 to 9 months.

Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization

Average eggs per season: 5.

Boreal owls provide considerable care for their young, both before and after hatching. Females stay near the nest about a week before egg laying. During this pre-fertilization time, males hunt for themselves and bring food back to their mate. After the clutch has been laid, males continue to provide food for females, but otherwise stay away from the nest. Females incubate the eggs, leaving once daily to eliminate waste. After hatching, males bring food for females and nestlings. Females tear food into smaller pieces that the nestlings can swallow, until they become big enough to eat prey whole. Brooding occurs as long as there is still young in the nest. The final young typically fledges after about 4 weeks from the start of incubation. Once the young have fledged, they stay close to the nest site for about a week, and both parents bring food to them at night, homing in on the begging calls of the fledglings. At the end of the week, the fledglings begin to move farther away, but are still fed for some time by the parents. They finally become independent about six to seven weeks after hatching.

Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Male, Female); pre-hatching/birth (Provisioning, Protecting: Female); pre-weaning/fledging (Provisioning: Male, Protecting: Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female)

Aegolius funereus is primarily monogamous. However, there have been documented cases of both bigyny (one male with two mates) and biandry (one female producing two clutches by two different mates). These cases have been observed only in Eurasia, and only when food is extremely plentiful. Males don't defend large foraging territories, but rather nest sites (old woodpecker holes), which are often in short supply. Fights between males have not been observed, and it appears that they compete for females through song and flight. Males will fly between perches near females, and sing a courtship song to attract female interest. If a female is interested, she will inspect the nest and, if she accepts it, she will simply stay there. The courtship period might last anywhere from 2 to 6 weeks for individual owls and from 1 to 4 months for the population as a whole.

Mating System: monogamous

Breeding season is variable, but takes place most commonly from March to June. Clutch size varies with food availability, but is typically around 4 or 5. Eggs are laid once every two days and brooding begins with the first egg, so hatching is asynchronous. Incubation is typically 28 days long. Young fledge about 30 to 31 days after hatching. The young are cared for by their parents for about a 6 weeks after fledging before setting out on their own. They become sexually mature in their first year, at around nine months old.

Breeding interval: Boreal owls typically breed once yearly. If food is plentiful then multiple clutches may occur.

Breeding season: Breeding season is highly variable, but is typically from the end of February to as late as July.

Range eggs per season: 2 to 7.

Average eggs per season: 5.

Range time to hatching: 25 to 32 days.

Range fledging age: 28 to 36 days.

Range time to independence: 6 to 7 weeks.

Range age at sexual or reproductive maturity (female): 9 to 9 months.

Range age at sexual or reproductive maturity (male): 9 to 9 months.

Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization

Average eggs per season: 5.

Boreal owls provide considerable care for their young, both before and after hatching. Females stay near the nest about a week before egg laying. During this pre-fertilization time, males hunt for themselves and bring food back to their mate. After the clutch has been laid, males continue to provide food for females, but otherwise stay away from the nest. Females incubate the eggs, leaving once daily to eliminate waste. After hatching, males bring food for females and nestlings. Females tear food into smaller pieces that the nestlings can swallow, until they become big enough to eat prey whole. Brooding occurs as long as there is still young in the nest. The final young typically fledges after about 4 weeks from the start of incubation. Once the young have fledged, they stay close to the nest site for about a week, and both parents bring food to them at night, homing in on the begging calls of the fledglings. At the end of the week, the fledglings begin to move farther away, but are still fed for some time by the parents. They finally become independent about six to seven weeks after hatching.

Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Male, Female); pre-hatching/birth (Provisioning, Protecting: Female); pre-weaning/fledging (Provisioning: Male, Protecting: Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female)

Female may occupy the nest cavity 1-3 weeks prior to egg laying (Hayward 1989). In Colorado, nests were initiated from mid-April to early June; mid-April to late May in Idaho (Hayward 1989). Clutch size usually is 4-6. Incubation reported as 25-36 days, by female. Young fledge at about 4-5 weeks, independent at 5-6 weeks, sexually mature by 1 year. Mating system variable. See Johnsgard (1988).

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 8
Specimens with Barcodes: 9
Species With Barcodes: 1

The following is a representative barcode sequence, the centroid of all available sequences for this species.

There are 8 barcode sequences available from BOLD and GenBank.  Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.  See the BOLD taxonomy browser for more complete information about this specimen and other sequences.

Download FASTA File

Aegolius_funereus is not endangered. They are rarely hunted by humans because of their small size. Further, humans don’t kill its prey, so it has a fairly stable food source. The only real impact made by humans on the species is destruction of habitat by harvesting trees for lumber. Nest boxes are sometimes placed on trees to provide nest sites. Since boreal owls are considered migratory, they are protected by the US Migratory Bird Act.

IUCN Red List of Threatened Species: least concern

US Migratory Bird Act: protected

US Federal List: no special status

CITES: appendix ii

Year Assessed

Assessor/s

Reviewer/s

Contributor/s

Justification

History

• 2008
  Least Concern
• 2004
  Least Concern

Aegolius funereus is not endangered. They are rarely hunted by humans because of their small size. Further, humans don’t kill its prey, so it has a fairly stable food source. The only real impact made by humans on the species is destruction of habitat by harvesting trees for lumber. Nest boxes are sometimes placed on trees to provide nest sites. Since boreal owls are considered migratory, they are protected by the US Migratory Bird Act.

US Migratory Bird Act: protected

US Federal List: no special status

CITES: appendix ii

IUCN Red List of Threatened Species: least concern

Canada

Rounded National Status Rank: N5 - Secure

United States

Rounded National Status Rank: N4 - Apparently Secure

Rounded Global Status Rank: G5 - Secure

Reasons: Wide range, apparently large numbers and occurrences seem to make this species secure.

Global Short Term Trend: Unknown

Comments: Unknown. Reliable populations number unavailable and nomadism caused by fluctuating prey density complicates this further (Hayward and Hayward 1993). Population "stable" in Canada (COSEWIC 1995 unpubl. report). Although recently discovered breeding far to the south of previously known locations, this is probably due the season and location of breeding (high elevation in February-April) rather than range expansion (Stahlecker and Duncan 1996).

Degree of Threat: C : Not very threatened throughout its range, communities often provide natural resources that when exploited alter the composition and structure over the short-term, or communities are self-protecting because they are unsuitable for other uses

Comments: Major threat may be indirect effects of forest harvesting practices. These may reduce primary prey populaitons, remove forest structure used for foraging, and eliminates nesting cavities (Hayward and Hayward 1993).

Preserve Selection and Design Considerations: Because of large home ranges and low population densities, planning (management) areas should exceed 1000 sq km of suitable habitat (Hayward 1989).

Management Requirements: Snag management guidelines for pileated woodpeckers should be followed (Rodrick and Milner 1991). Aspen groves with large diameter trees should be maintained. Uneven-age timber management may be compatible, but clearcuts are not considered suitable habitat for foraging (Hayward 1989).

Global Protection: Many to very many (13 to >40) occurrences appropriately protected and managed

Comments: Many EOs are probably in designated Wilderness areas in the U.S. including the Selway-Bitterroot in Montana.

There are no known adverse effects of A._funereus on humans.

Aegolius_funereus has very little impact on humans, aside from its role as a predator of small mammals which humans might consider pests.

Positive Impacts: controls pest population

There are no known adverse effects of A. funereus on humans.

Aegolius funereus has very little impact on humans, aside from its role as a predator of small mammals which humans might consider pests.

Positive Impacts: controls pest population