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Surnia ululanorthern hawk owl(Also: northern hawk-owl)

By Smita Kalokhe

Geographic Range

Surnia ulula (also known as the Northern Hawk Owl) is found primarily in North America. It ranges from northern Alaska, through lower and middle Canada, and along the northern region of the United States. This species has also spread through northern Russia and Scandinavia (de la Torre, 1990).

Habitat

Surnia ulula lives primarily in dense coniferous or coniferous-deciduous forests, which adjoin open areas. It prefers mountainous ranges where open areas and perches are readily available. The abundance of prey dictates location of habitats (Duncan and Duncan, 1998). This species will not inhabit dark impenetrable spruce-fir forests

(Voous,1988).

Physical Description

Northern Hawk Owls' plumage is compact, in contrast to the down feathers of boreal owls (Voous, 1988). They are dark chocolate in color with white spots. The breast and belly regions are creamy white crossed by horizontal, cinnamon brown bars. Their poorly developed facial disks are framed by black lines. Often referred to as the "earless" owl, they lack true ear tufts; the external ear openings are elliptical (de la Torre, 1990). Both legs are fully feathered (Duncan and Duncan, 1998).

  • Range mass
    343.9 to 348.9 g
    12.12 to 12.30 oz
  • Range length
    35.56 to 43.18 cm
    14.00 to 17.00 in
  • Average length
    39.37 cm
    15.50 in
  • Range wingspan
    78.74 to 88.9 cm
    31.00 to 35.00 in

Reproduction

Northern Hawk Owls are generally monogamous. However, in captivity a male may mate with two females. Males attract females by clapping their wings while in flight and making Advertising Calls while perched. Females respond with their own Advertising Calls. Males court by bringing food to the nest and the females. Before and after copulation, both males and females sing (Duncan and Duncan, 1998).

The female lays the first egg, which immediately starts the incubation period. Between eggs, there is an interval of approximately 1.6 days. When the female is off the nest, the male does not incubate the eggs. The male provides food and protection against predators.The female owl incubates the eggs for 25-29 days. Before they hatch, the young start to call. After the eggs have hatched, the young are tended to by the female. Eggshells are either eaten or removed from nest. The female broods the young for approximately 10 days. Three to five weeks after hatching, the young leave the nest (Duncan and Duncan, 1998; Nero, 1995).

  • Breeding season
    March 30 - June 30
  • Range eggs per season
    3 to 13
  • Average eggs per season
    7
  • Range time to hatching
    25 to 30 days
  • Range fledging age
    3 to 5 weeks

Immediately after hatching has occurred, brooding begins. During this time, the male brings food to the female, which then gives it to the young. Brooding lasts approximately 10 to 14 days. While the male will offer small intact prey to the young, primary care and feeding is provided through the female (Duncan and Duncan, 1998).

Lifespan/Longevity

Expected lifespan in both captivity and wild is 10 years (Duncan and Duncan, 1998).

  • Average lifespan
    Status: wild
    10 years
  • Average lifespan
    Status: wild
    10 years
  • Average lifespan
    Status: captivity
    8.2 years
    AnAge

Behavior

Surnia ulula rarely walks on the ground. A waddle-like motion characterizes its walk. Its flight is "rapid and strong." When moving from one perch to another, it quickly dives down, stays low, and then abruptly flies up to the new perch. The Northern Hawk Owl participates in self-maintaining behavior through preening and snow-bathing. These animals are primarily diurnal but may also be active at night. A male establishes its territory a few weeks before nesting and attracts a female to the nest site through an Advertising Call (Duncan and Duncan, 1998)

Communication and Perception

Food Habits

Northern Hawk Owls prey on small mammals (voles, lemmings, mice, shrews, snowshoe hares, cottontails, moles, squirrels and rats). During the summer, they consume primarily rodents, and in the winter they shift to birds (ptarmigan and grouse). The extent to which they prey on birds is unknown. They share similar hunting habits with boreal owls. They hunt both during the day and the night (Duncan and Duncan, 1998).

  • Primary Diet
  • carnivore
    • eats terrestrial vertebrates
  • Animal Foods
  • birds
  • mammals

Predation

The Great Horned Owl serves as the Northern Hawk Owl's primary predator. At night the Great Horned Owls kill roosting owls while they are resting or enter nests and take eggs or young. To avoid predation, the Northern Hawk Owl flattens its plumage and stands erect. Also, it attempts to intercept predators that attack its nest (Duncan and Duncan, 1998).

Ecosystem Roles

There has been minimal research performed on this species, and therefore, this information is not available.

Economic Importance for Humans: Positive

In particular during the summer months, the Northern Hawk Owl plays a significant role in controlling the rodent population; rodents may make up as much as 90% of their diet (Lockshaw, 2001).

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

These birds not pose a serious threat to humans. They allow humans to come relatively close to them. However, invading their territory may cause an owl to bite or attack (Duncan and Duncan, 1998)

Conservation Status

The Northern Hawk Owl has historically been shot down by some native groups for consumption. The number of owls affected by this is small.

Contributors

Smita Kalokhe (author), University of Michigan-Ann Arbor, Kerry Yurewicz (editor), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

acoustic

uses sound to communicate

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

internal fertilization

fertilization takes place within the female's body

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

visual

uses sight to communicate

References

Duncan, J., P. Duncan. 1998. Northern Hawk Owl. Pp. 1-20 in F Gill, A Poole, eds. The Birds of North America, No. 256. Washington, D.C.: Academy of Natural Sciences, Philadelphia, PA , and American Ornithologists Union.

Lockshaw, D. 2001. "Owling,Com: Northern Hawk Owl Biology" (On-line). Accessed March 13, 2002 at http://owling.com/N-Hawk_nh.htm.

Nero, R. 1995. Notes on a Wintering Northern Hawk Owl in Manitoba. Blue Jay, 53: 205-215.

Voous, K. 1988. Owls of the Northern Hemisphere. Cambridge, Massachusetts: MIT Press.

de la Torre, J. 1990. Owls: Their Life and Behavior. New York: Crown Publishers, Inc..

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