Spotted Owl Life History

Habitat

Habitat ForestsOver the full extent of their range, Spotted Owls occur in a variety of habitat types centered around mature forests with dense canopies. The Northern Spotted Owl requires unlogged, expansive, mature coniferous forest stands with large trees and a complex array of vegetation types, sizes and ages. This subspecies tends to avoid crossing clearcut, recently logged, or brushy areas, but will forage in redwood forests that have been previously logged if some old and large trees remain. The California Spotted Owl similarly prefers forest stands with large-diameter trees and varied levels of vegetation. In areas up to about 3,300 feet above sea level, this subspecies lives among oak and other hardwoods; at higher altitudes it's more often found in conifers. The Mexican subspecies inhabits pine-oak forests or mixed-conifer forests dominated by Douglas-fir, pine, or fir. It also roosts and nests in steep, narrow canyons.Back to top

Food

Food MammalsSpotted Owls eat mainly small and medium-sized mammals, especially rodents. The two dominant food items for both the Northern and California Spotted Owl are flying squirrels and dusky-footed woodrats; the Northern subspecies' range is limited to areas where these two animals are available. Other common prey animals, some shared by all three subspecies, include bushy-tailed woodrats, mice, red tree voles, red-backed voles, snowshoe hares, brush rabbits, pocket gophers, and bats. Non-mammal prey animals include smaller owls and other birds, amphibians, and insects. Spotted Owls hunt mostly in the dark—starting as early as an hour before sunset, using several different foraging sites in a single night, and stopping just before sunrise. The owls hunt from perches, detecting prey by sight and sound. Gliding silently down on their quarry, they snatch it up in their talons. These owls also capture prey in midair or pluck it from branches. They kill prey by breaking the animals' necks with their bills.Back to top

Nesting

Nest Placement

Nest CavityThe male Spotted Owl probably selects the nest site—normally in a dense section of old forest, well protected from open sky by a dense tree canopy. He might choose a broken-off treetop or tree-trunk hollow, a mistletoe tangle, or an old nest left behind by a squirrel or a bird of prey. In areas with relatively little forest habitat, some Mexican Spotted Owls nest on ledges and potholes in narrow, steep-sided canyons. Pairs may reuse a nest site over many years, though most pairs do not nest every year.

Nest Description

The female scrapes out a shallow depression in debris found at the site, but adds at most only a few feathers as nest material. Diameters of nests created by the Northern Spotted Owl have been measured from 15 to 23 inches. Spotted Owls will use artificial nest cavities.

Nesting Facts
Clutch Size:1-4 eggs
Egg Length:1.9-2.2 in (4.8-5.5 cm)
Egg Width:1.6-1.9 in (4.1-4.7 cm)
Incubation Period:28-32 days
Nestling Period:34-36 days
Egg Description:White to pearl gray.
Condition at Hatching:Helpless, eyes closed, covered in white down.
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Behavior

Behavior Aerial Dive (ground/talons)Though not especially swift, Spotted Owls are agile and maneuverable fliers, interspersing gliding flight with quick wingbeats. Except when dispersing from natal territory, they don't tend to fly above the canopy or travel long distances. Spotted Owls move up and down in the canopy to adjust to temperature changes, which may be one reason they require the complex, multilayered vegetation provided by old-growth forests. Adult Spotted Owls are solitary except for interactions with their mates and young. They form long-term monogamous pair bonds, remaining year-round in the same home range. Pairs begin roosting and interacting together 4–6 weeks before eggs are laid. Roosting owls frequently preen themselves and each other. The female incubates the eggs by herself, leaving the nest only briefly during incubation to defecate, regurgitate pellets, defend the nest, or receive food from the male. Around 8–10 days after the eggs hatch, she begins leaving the nest for progressively longer hunting forays. Young Spotted Owls remain in the nest for the first 4–5 weeks after hatching. Once out of the nest, they stay close to their parents for another 2–3 months, becoming independent by late summer. After reaching adult weight, they disperse from their natal areas in September and October. Back to top

Conservation

Conservation DecliningSpotted Owl populations have declined sharply as a result of habitat loss in the ranges of all three subspecies. Partners in Flight estimates the global breeding population at 15,000 individuals, with 56% in the U.S., 4% in Canada, and 40% in Mexico. The species rates a 15 out of 20 on the Continental Concern Score and is listed as a Tri-National Concern Species. The U.S. Fish and Wildlife Service lists both the Northern and Mexican subspecies as Threatened; both these subspecies are also on the 2016 State of the Birds Watch List, which lists bird species that are at risk of becoming threatened or endangered without conservation action. Ornithologists began sounding alarms over the fate of the Northern Spotted Owl in the mid-1970s, but federal listing of the subspecies took nearly two decades. The listing process was a contentious legal battle hampered by lack of population-trend and habitat-loss data and by the high commercial value of old-growth forests. After the Northern Spotted Owl was listed, it became the object of resentment and criticism from the logging industry and other groups that felt the species was being placed above the welfare of local economies. The species' protection did help reduce old-growth logging on federal land (though it continued on some state and private lands), but the species' decline continued. Primary threats to Spotted Owl populations are loss of old-growth forest through clearcutting and degradation of habitat through forest management, urban and suburban expansion, water and agricultural development, and mining. Competition from and interbreeding with the Barred Owl now pose an additional threat. Forests that are selectively logged, leaving behind large trees with cavities, snags, and woody debris, may be reoccupied by Spotted Owls within 40–100 years. Spotted Owls' main predators are other raptors, including the Northern Goshawk and Great Horned Owl, both of which occasionally nest in the same forest stands. Common Ravens have been observed attempting to steal Spotted Owl eggs. Fishers—carnivorous relatives of weasels—may also prey on both eggs and young.Back to top

Credits

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

Gutiérrez, R. J., A. B. Franklin and W. S. Lahaye. 1995. Spotted Owl (Strix occidentalis), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Lutmerding, J. A. and A. S. Love. Longevity records of North American birds. Version 2015.2. Patuxent Wildlife Research Center, Bird Banding Laboratory 2015.

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

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

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