Northern Hawk-owl

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Image:NorthHawkOwl.jpg

Common Name: Northern Hawk-owl
Scientific Name: Surnia ulula

Size: 14.2-17.6 inches (36-44.7 cm); Wingspan: 43.3-47.2 inches (110-120 cm)

Habitat: Northern Hemisphere; from eastern Alaska through to Newfoundland and in some areas extends south into northern United States and across northern Eurasia and central China.

They are unevenly distributed and highly variable throughout the boreal forest. They live mostly in open coniferous forests, or coniferous forests mixed with deciduous species such as larch, birch, poplar, and willow. They are found in muskegs, clearings, swamp valleys, meadows, or recently burnt areas, and generally avoid dense spruce and fir forests.

Status: Least Concern. Global population: 130,000 adult individuals with a fluctuating population trend. Populations are known to fluctuate with cycles of small rodents and irruptions are known to occur in sub-boreal regions throughout the world. In Scandinavia, populations have been reported to vary from a few hundred birds in certain years to over 4000 birds in others and even up to 10 000 breeding pairs in optimal years. Irruptions can be used as indicators of small mammal abundance and in eastern North America, southern irruptions have been linked with low densities of red-backed voles in the high boreal forest.

Diet: Mostly small rodents, mammals and a variety of birds. In Eurasia, the northern hawk-owl is known to feed primarily on voles from the Microtus family. Other animals that are important prey items for the northern hawk-owl include the red squirrel (Sciurus vulgaris), mice, rats, lemmings, the short-tail weasel (Mustela erminea), partridge, spruce grouse (Falcipennis canadensis), doves, pileated woodpeckers (Dryocopus pileatus), sparrows, jays, robins, starlings, buntings, grackles, and finches.

The northern hawk-owl is a partially diurnal hunter, although it has been recorded hunting at varying times and does not appear to have a preferred hunting time. It will perch and scour the immediate area for prey. They likely do not stay put for long if the site is not producing prey. The hawk-owl prefers open, forest-type environments when perching.

Nesting: Males and females are alike however females are slightly larger than males. They have relatively dark brown with an off-white spotting pattern on all dorsal parts of the body. The exception of the back of the neck which has a distinct black v-shaped pattern. The underbelly is generally white or off-white which continues to the toes with brown bands on the breast and stomach. It also boasts a long tail with brown banding. The northern hawk-owl has a smokey white face with a black border, a flat head, yellow eyes and a yellow curved beak.

The northern hawk-owl generally starts its mating rituals at the beginning of March. After calling and pairing is complete the northern hawk-owl will build a nest and start to lay eggs. On average the northern hawk-owl will lay 3–11 eggs per brood. The nest sites are usually the tops of hollow stumps of old dead spruce trees. These nesting sites are usually 2–10 m (6.6–32.8 ft) above ground for the North American and approximately 4–5 m (13–16 ft) above ground for the Eurasian.

For the most part the female northern hawk-owl does the incubating of the eggs whilst the male forages for food. Once the chicks have hatched their roles shift drastically. At about two weeks into the chicks lives the female starts to leave the nest for long spans of time (5 hours or more). This span of time is presumably when the female hunts. The male however, will guard the nest diligently until the chicks leave. When predators (usually other raptors) fly nearby, the male will sometimes chase them away from the nest if they feel it is necessary. Once the owlets have grown to a size which allows less parental supervision, they will leave the nest. This occurs on average after their 21st day, and can begin as early as mid-June. After this the female will provide most of the care. However the male will remain close and will still feed his young on occasion. The northern hawk-owl has also been known to nest on cliff sides. It has little fear of humans, and will attack if the young are approached too closely.

Cool Facts: The northern hawk-owl has been said to resemble a hawk in appearance and in behavior. In North America, its appearance in flight is often considered similar to a Cooper's hawk (Accipiter cooperii). It has been suggested that this may be because the hawk-owl may partially fill an important diurnal niche similar to that of day hunters such as hawks.

When alerting to danger, the northern hawk-owl lets out a sound similar to rike, rike, rike, rike. It also releases a high pitched scream followed by a yip when an intruder is near to the nest. To warn of impending dangers to a fledgling, the hawk-owl will let out a noise similar to ki ki kikikikiki. Calls can vary in length from 15 s to 2 min.

Three subspecies exist across the northern holarctic:

  • S. u. caparoch. The North American subspecies spans from eastern Alaska through to Newfoundland and in some areas extends south into northern United States.
  • S. u. Tianschanica. Breeds in central Asia reaching Xinjiang (China)
  • S. u. ulula. It is found across Eurasia reaching Siberia at its most eastern range.


Found in Songbird ReMix Owls of the World Volume 2

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