Northern Hawk Owl Life History

Habitat

Habitat Forests

Northern Hawk Owls reside in open coniferous or mixed forests bordering open areas or marshes dotted with trees that provide good perches. Burned areas of the boreal forest also provide good nest sites and foraging areas. During years of southern irruptions, they frequent wooded farmlands, lakeshores, and pastures or prairies with perches.

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Food

Food Mammals

Northern Hawk Owls eat small mammals, especially voles in the summer. They tend to supplement this diet with birds such as ptarmigan and grouse in the winter.

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Nesting

Nest Placement

Nest Cavity

Males and females pick a nest site that tends to be in open forests with scattered trees or along the forest edge, often near water.

Nest Description

Northern Hawk Owls nest in holes in trees created by woodpeckers or in naturally decayed hollows and broken tree trunks. They do not add material to the nest hole, but the floor of the nest hole tends to accumulate pellets and fur from prey brought into the nest. They primarily nest in holes or hollows, but they occasionally use old stick nests, cliffs, or, in Norway and Sweden, nest boxes.

Nesting Facts
Clutch Size:3-13 eggs
Number of Broods:1 brood
Egg Length:1.2-1.3 in (3.1-3.2 cm)
Egg Width:1.5-1.6 in (3.9-4.2 cm)
Incubation Period:25-30 days
Nestling Period:20-35 days
Egg Description:White.
Condition at Hatching:Helpless and covered in white down.
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Behavior

Behavior Aerial Dive (ground/talons)

Northern Hawk owls hunt primarily by day, but also at night, watching and listening for prey from prominent perches. They lean forward on their perches, scanning below for small mammals. When they spot something, they leap off their perch, plummet to the ground and fly low across open areas with strong and deep wingbeats before swooping back up to perch atop another tree with prey in their talons. Northern Hawk Owls take advantage of abundant prey by caching small mammals to eat later, storing them in tree crevices, holes in trees, or among dense spruce boughs. Hunting and courting take place within their territory during the breeding season. A male trying to court a female flies in circles with its wings held stiff while singing; then he lands on a prominent perch where he starts to call for a mate. Once paired, the male offers food to his mate and continues to feed her during incubation. Pairs stay together for a single breeding season. Northern Hawk Owls tend to be solitary year-round but seem relatively tolerant of other birds including other owls within their territory. But they are not tolerant of intruders including humans at the nest site and will attack any intruder that comes near. When birds mob them or a predator shows up they sleek down their feathers and close their eyes making themselves look thinner and less obtrusive.

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Conservation

Conservation Low Concern

Northern Hawk Owls are uncommon. Their northern boreal habitats make assessing populations difficult and their populations are not surveyed by the North American Breeding Bird Survey. Partners in Flight estimates the global breeding population at 200,000 individuals. The species rates an 11 out of 20 on the Continental Concern Score, which means it is not on the Partners in Flight Watch List and is a species of low conservation concern. Populations likely fluctuate with availability of small mammal prey that tend to have boom and bust cycles. Forestry practices that clearcut large swaths of boreal forest likely reduce nesting sites and hunting perches for Northern Hawk Owls.

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Credits

Duncan, James R. and Patricia A. Duncan. 2014. Northern Hawk Owl (Surnia ulula), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Dunne, P. (2006). Pete Dunne's essential field guide companion. Houghton Mifflin Harcourt, New York, USA.

Lutmerding, J. A. and A. S. Love (2016). Longevity records of North American birds. Version 2016.1. Patuxent Wildlife Research Center, Bird Banding Laboratory, Laurel, MD, USA.

Partners in Flight (2017). Avian Conservation Assessment Database. 2017.

Sauer, J. R., D. K. Niven, J. E. Hines, D. J. Ziolkowski, Jr., K. L. Pardieck, J. E. Fallon, and W. A. Link (2017). The North American Breeding Bird Survey, Results and Analysis 1966–2015. Version 2.07.2017. USGS Patuxent Wildlife Research Center, Laurel, MD, USA.

Sibley, D. A. (2014). The Sibley guide to birds, second edition. Alfred A. Knopf, New York, USA.

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