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).
These animals are found in the following types of habitat:
temperate 
; terrestrial .
Physical Description
(12.11 to 12.28 oz; avg. 12.19 oz)
(14 to 17 in; avg. 15.5 in)
(31 to 35 in; avg. 33 in)
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).
Some key physical features:
endothermic ; bilateral symmetry .
Reproduction
March 30 - June 30
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).
Mating systems:
monogamous .
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).
Key reproductive features:
iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (internal ); oviparous .
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).
Parental investment:
altricial ; female parental care .
Lifespan/Longevity
Expected lifespan in both captivity and wild is 10 years (Duncan and Duncan, 1998).
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)
Key behaviors:
flies; nocturnal ; motile ; territorial .
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
- great horned owls (Bubo virginianus)
- northern goshawks (Accipiter gentilis)
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: 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)
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).
Ways that people benefit from these animals:
controls pest population.
Conservation Status
IUCN Red List: [link]:
Least Concern.
US Migratory Bird Act: [link]:
Protected.
US Federal List: [link]:
No special status.
CITES: [link]:
Appendix II.
State of Michigan List: [link]:
No special 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.
Kerry Yurewicz (editor), University of Michigan.
