The northern hawk-owl or northern hawk owl (Surnia ulula), is a medium-sized true owl of the northern latitudes. It is non-migratory and usually stays within its breeding range, though it sometimes irrupts southward. It is one of the few owls that is not strictly nocturnal nor crepuscular, often being active during the day. This is the only living species in the genus Surnia of the family Strigidae, the "typical" owls (as opposed to barn owls, Tytonidae). The species is sometimes called simply the hawk owl; however, many species of owls in the genus Ninox are also called "hawk owls".

Taxonomy

The northern hawk-owl was formally described by the Swedish naturalist Carl Linnaeus in 1758 in the tenth edition of his Systema Naturae under the binomial name Strix ulula. The owl is now the only species placed in the genus Surnia that was introduced in 1805 by André Duméril. The type species was designated by George Robert Gray in 1840 as the northern hawk-owl. The genus name is of unknown etymology and may simply have been invented by Duméril. The specific epithet ulula is Latin for a "screech owl".

A molecular phylogenetic study of the owls published in 2019 found that the northern hawk-owl is sister to a clade containing the pygmy owls in the genus Glaucidium.

Three subspecies are recognised:

  • S. u. ulula (Linnaeus, 1758) – northern Eurasia
  • S. u. caparoch (P. L. S. Müller, 1776) – northern North America

Description

thumb|left|Subspecies S. u. caparoch, Sax-Zim Bog, Minnesota

Male northern hawk-owls are generally long, and weigh about . Females are slightly bigger with a length of and a weight of about . Both male and female have similar wingspans of about . The plumage is relatively dark brown with an off-white spotting pattern on all dorsal parts of the body with the exception of the back of the neck which boasts a 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 has a long tail with brown banding; the tail feather tips are rounded in adults, and pointed in first-year birds.

The subspecies vary in size and plumage tone; S. u. ulula has paler underparts with fine bars, while S. u. caparoch is browner below with heavier barring. S. u. tianschanica is marginally the largest, and darker above than the other two, but with intermediate barring below.

The northern hawk-owl resembles a hawk in appearance and in behaviour. In North America, its appearance in flight is often considered similar to a Cooper's hawk (Astur 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. The North American subspecies S. u. caparoch spans from eastern Alaska through Canada to Newfoundland and in some areas extends south into northern United States. Frogs and even fish are sometimes taken. In the winter, feeding strategies change; where in summer the main source of food is mammals, in the winter a bigger portion of the hawk-owl's prey biomass consists of ground-dwelling birds, such as ptarmigan and grouse.

In Yukon, northern hawk-owl densities were estimated to be between zero and six pairs per . Compared to the nineteenth century, southern irruptions in the New and Old World appear to have declined. Downes et al. (2000) considered the hawk-owl to be of medium concern, but with a high priority to improve monitoring.

In falconry

The northern hawk-owl is considered a falconry bird in Ontario, and may be used to hunt small game with a proper license.

  • Northern Hawk-Owl Species Account – Cornell Lab of Ornithology
  • Northern Hawk-Owl – eNature.com
  • Northern Hawk-Owl information at owlpages.com
  • Northern Hawk-Owl profile at the Government of Canada Species at Risk Public Registry
  • Northern hawk-owl. Video of male, female and chicks.