The northern spotted owl is a medium-sized, dark brown owl with a barred tail, white spots on the head and breast, and dark brown eyes surrounded by prominent facial disks.  Males and females have similar plumage, but females typically weigh 10 to 20 percent more than males.

The northern spotted owl is one of three spotted owl subspecies: northern, California (Strix occidentalis occidentalis), and Mexican (Strix occidentalis lucida).  The distribution of the northern subspecies includes southwestern British Columbia, western Washington and Oregon, and northwestern California south to Marin County.  The southeastern boundary of its range is the Pit River area of Shasta County, California.

The spotted owl is a relatively long-lived bird; produces few, but large young; invests significantly in parental care; experiences later or delayed maturity; and exhibits high adult survivorship.  Spotted owls are territorial, however, home ranges of adjacent pairs can overlap.   Home range size varies by province and generally increases from south to north.

Spotted owls do not typically reach sexual maturity until after 2 years of age and when they pair, they are monogamous.  Adult females lay an average of 2 eggs per clutch with a range of 1 to 4 eggs.  Spotted owl pairs do not typically nest every year, nor are nesting pairs successful every year. 

Spotted owls are mostly nocturnal, but they may forage opportunistically during the day.  Northern flying squirrels (Glaucomys sabrinus) and woodrats (Neotoma spp.) are usually the predominant prey.  Other prey species such as the red tree vole (Arborimus longicaudus), red-backed voles (Clethrionomys gapperi), mice, rabbits and hares, birds, and insects may be seasonally or locally important.

Northern spotted owls generally inhabit older forested habitats because they contain the structural characteristics required for nesting, roosting, and foraging.  Specifically, northern spotted owls require a multi-layered, multi-species canopy with moderate to high canopy closure.  The stands typically contain a high incidence of trees with large cavities and other types of deformities; large snags (standing dead trees); an abundance of large, dead wood on the ground; and open space within and below the upper canopy for spotted owls to fly.  Recent landscape-level analyses suggest that in some parts of the subspecies’ range a mosaic of older forest habitat interspersed with other vegetation types may benefit northern spotted owls more than large, homogeneous expanses of older forests.  In redwood (Sequoia sempervirens) forests along the coast range of California, northern spotted owls may be found in younger forest stands that contain structural characteristics of older forests.

The current level of survey coverage and effort are insufficient to produce reliable population estimates.  Consequently, other indices, such as demographic data, are used to evaluate the current condition of the northern spotted owl population.  Analysis of demographic data can provide an estimate of population trend (i.e., lambda (λ)).  Estimated lambdas from the most recent meta-analysis for the listed range of the subspecies indicate declines in populations in some areas and not in others. 

Approximately 7.4 million acres of suitable habitat were estimated to exist on Federal lands in 1994.   A recent trend analysis indicated an overall decline of approximately 2 percent in the amount of suitable habitat on Federal lands within the Northwest Forest Plan area between 1994 and 2003.  There are insufficient data to determine the amount and trend in suitable habitat on non-Federal lands.  In general, the amount of spotted owl habitat continues to decline on a range-wide basis, although at a rate that is less than in the years prior to the species’ listing, particularly on Federal lands within the Northwest Forest Plan boundary. 

The northern spotted owl was listed as threatened throughout its range primarily due to loss and adverse modification of suitable habitat as a result of timber harvesting and exacerbated by catastrophic events such as fire, volcanic eruption, disease, and wind storms.  At the time of listing, small and isolated populations vulnerable to extinction, predation and competition were also identified as threats.  Since listing of the northern spotted owl, recent reviews have more specifically identified competition with the barred owl (Strix varia), and fire in the relatively dry East Cascades and Klamath provinces of California and Oregon as greater threats than previously considered.  New potential threats of unknown magnitude to the subspecies and its habitat include West Nile virus and the sudden oak death tree disease, respectively.

The Northwest Forest Plan is the current conservation strategy for the northern spotted owl on Federal lands.  It established a forest reserve-based system designed to address the conservation needs of the northern spotted owl by providing for suitable habitat managed across a variety of ecological conditions within the spotted owl’s range to reduce risk of local or widespread extirpation.  The reserve system is designed to provide for large blocks of suitable habitat to support clusters or local population centers of spotted owls throughout the owl’s range that are spaced closely enough to facilitate survival and dispersal between the blocks.

The primary expectation for private land is for it to contribute demographic support to and/or connectivity with Northwest Forest Plan lands.  In addition, each State may promulgate rules which govern timber harvest and protect the northern spotted owl and/or its habitat to varying degrees on private land.  In California, State Forest Practice Rules, which govern timber harvest on private lands, require northern spotted owl surveys in suitable habitat and provide for protection of habitat around nest areas.  In some areas, private lands are managed under Habitat Conservation Plans for the northern spotted owl.

• Revised Designation of Northern Spotted Owl Critical Habitat (pdf, 2.5 MB)
• Recovery Plan for the Northern Spotted Owl (pdf, 4.0 MB)
• Scientific Review of the Draft Northern Spotted Owl Recovery Plan and Reviewer Comments (pdf, 1.3 MB)
• Northern Spotted Owl Five-year Review: Summary and Evaluation
• Scientific Evaluation of the Status of the Northern Spotted Owl (pdf, 2.4 MB)
• Protocol for Surveying Proposed Management Activities that "May Impact" Northern Spotted Owls
• Estimating the Effects of Auditory and Visual Disturbance of NSO and MM in Northwestern California (pdf, 1.5 MB)
• Conservation Strategy for the Northern Spotted Owl (pdf, 4 MB)