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Northern Spotted Owl

Scientific Name: Strix occidentalis caurina

Listing: The Washington, Oregon and California population of the northern spotted owl, was federally listed as threatened under the Endangered Species Act in 1990.

Critical Habitat: Critical habitat for the northern spotted was originally designated in in 1992.  The critical habitat designation was revised in 2012, following the publication of the final revised recovery plan.  Critical habitat for the spotted owl now includes over 9.5 million acres of federal lands in California, Oregon, and Washington. 

A final revised recovery plan was published in July 2011. 

  • Historical Status and Current Trends

    The northern spotted owl is believed to have historically inhabited most forests throughout southwestern British Columbia, western Washington and Oregon, and northwestern California as far south as San Francisco Bay.

    There are no current estimates of the total population size of northern spotted owls because many areas across the range of the subspecies remain unsurveyed.  Spotted owl population studies use estimates of reproduction and survival to determine if populations within discrete study areas are increasing, stationary, or decreasing.  These studies indicate that the average rate of population decline is 3.8% per year across the subspecies range, but rates of decline vary from 1.2 to 8.4 percent per year depending on location. More stable populations occur in southern Oregon and northern California, while the populations in Washington and northern Oregon are all declining at a rate of 3 to 8.4 percent per year.  The factors that influence spotted owl populations are not fully understood, but habitat quality and quantity, annual weather patterns, and the presence of barred owls are all factors that affect spotted owl survival, reproduction, and local population trends.

    Habitat

    Northern spotted owls live in forests characterized by dense canopy of mature and old-growth trees, abundant logs, standing snags, and live trees with broken tops. Although they are known to nest, roost, and feed in a wide variety of habitat types, spotted owls prefer older forest stands with variety: multi-layered canopies of several tree species of varying size and age, both standing and fallen dead trees, and open space among the lower branches to allow flight under the canopy. Typically, forests do not attain these characteristics until they are at least 150 to 200 years old.

    Description and Life History

    The northern spotted owl is one of three recognized subspecies of spotted owls, including the Mexican spotted owl (S.o. lucida) and the California spotted owl (S.o. occidentalis). Northern spotted owls are a medium-sized, chocolate brown owl with dark eyes, with round or irregular white spots on the head, neck, back, and underparts.  Spotted owls are long-lived, non-migratory birds that establish territories that they defend against other owls.  Spotted owls range across their territories hunting for prey, usually small forest mammals such as flying squirrels, woodrats, voles, and mice.  The northern spotted owl is a nocturnal "perch-and-pounce" predator that captures its prey with its claws. Like most owl species, the northern spotted owl nests in trees.  Spotted owls do not build a nest.  They use large cavities in old trees, or nest on a natural platform created by a large broken tree top or other natural tree deformity large enough to provide a stable nest site.  

    Spotted owls primarily mate for life and may live up to 20 years. Although the breeding season varies with geographic location and elevation, spotted owls generally nest from February to June. One to four (usually two) pure white eggs are laid in the early spring and hatch about a month later. During incubation, the male typically does most of the foraging and brings food to the female and the young owlets. At three to four weeks of age, the owlets are able to perch away from the nest, but still depend on their parents for food. Predation on these juveniles by great horned owls and other predators is high at this time and many do not survive. Parental care of the juveniles generally lasts into September when the young owls finally take off on their own. This period, too, is hard for the young birds, and starvation is common in the first few months on their own.  Juvenile spotted owls live as non-territorial “floaters” for 2 to 5 years before they mature and establish nesting territories of their own. 

    Reasons for Decline

    The historical loss of nesting, roosting, and foraging habitat was a major cause of the northern spotted owl’s decline over the past century.  Habitat loss is still considered to be a threat to the northern spotted owl, as habitat continues to be lost to wildfires, timber harvest, and other natural disturbances.  

    Northern spotted owl populations continue to decline, especially in the northern parts of the subspecies’ range, where populations have declined by as much as 77 percent since 1990.  Over the past decade it has become apparent that competition from the barred owl (Strix varia) now poses a significant threat to the northern spotted owl.  Barred owls compete directly with spotted owls for habitat and resources for nesting, roosting, and foraging.

    Habitat loss is still considered to be a threat to the spotted owl, as habitat continues to be lost to wildfires, timber harvest, and other natural disturbances. Wildfire has been the major cause of habitat loss on federal lands (e.g., National Forests and National Parks), where most spotted owl habitat is protected from timber harvesting by protective land management plans.  Timber harvest continues to be the primary cause of habitat loss on non-federal lands. 

    Conservation Measures

    Recovery efforts for the northern spotted owl are helping to reduce habitat loss on federal lands. Although the need for timber necessitates continued harvesting, current forest management practices stress more limited harvesting in old-growth forests and suggest alternate areas for harvest which are less preferred by spotted owls. Careful planning of timber sales and forest conservation are necessary to halt the decline of the spotted owl and other old-growth species. The Northwest Forest Plan, created in 1994, established a system of late-successional reserves (LSR) across the range of the spotted owl to provide suitable nesting habitat over the long term. The federal forest lands outside these reserves are managed to allow dispersal between the LSRs through riparian reserves and other land allocations. In 2011, we issued a Revised Recovery Plan for the Northern Spotted Owl that contains a wide array of recommendations, including protecting high-quality and occupied spotted owl habitat, actively managing forests to restore their health, and managing competition from the encroaching barred owl. We are currently conducting an experimental removal of barred owls from spotted owl habitat to assess the effect on spotted owls. A new final rule designating critical habitat was published in December 2012.

    References and Links

    Regulatory Information

    Northwest Interagency ESA Website: Information on the Endangered Species Act (ESA) and Streamlined Consultation Process. Website

    Recovery Plan

    Revised Recovery Plan for the Northern Spotted Owl (Strix occidentalis caurina

    https://www.fws.gov/pacific/ecoservices/documents/RevisedNSORecPlan2011.pdf

    Status Reviews

                5-Year Status Review 2011: Short Form Summary. Report

    5-Year Status Review 2004: Scientific evaluation of the status of the Northern Spotted Owl. Sustainable Ecosystems Institute, Portland, Oregon. Report

    Conservation Strategy: Conservation Strategy for the Northern Spotted Owl. Interagency Scientific Committee. Portland, Oregon. May 1990. Report (p

    Northwest Forest Plan – The First 20 Years (1994-2013): Status and Trends of Northern Spotted Owl Habitats 

    http://www.reo.gov/monitoring/reports/20yr-report/

    Survey Protocols

    California NSO Survey Protocol

    Revised NSO Survey Protocol - 2012

    Northwest Forest Plan

    20-Year Monitoring Reports: Report 

    http://www.reo.gov/monitoring/reports/20yr-report/

    Regional Ecosystem Office: Northwest Forest Plan Website

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