Northern Spotted Owl

Renée Cormier (PRBO Conservation Science); Dave Press (National Park Service)

Status: Stable

In the San Francisco Bay Area (primarily Marin County), Northern Spotted Owls nest in both old-growth and mature second-growth forests of Douglas-fir, coast redwood, bishop pine, mixed conifer–hardwood, and other evergreen hardwood trees. This varies from the rest of the population of Northern Spotted Owls in the Pacific Northwest, where they are commonly associated with mature coniferous forests. In Marin County, unique forest types are Bishop pine and evergreen forests.

Percent of Northern Spotted Owl sites surveyed that were occupied by a pair. All sites are not surveyed every year; however, sites surveyed likely reflect the overall population of owls in Marin County. In general, the number of Northern Spotted Owls in Marin County appears stable.

Except for 2007 when almost no young were produced, Spotted owl fecundity (reproductive success) appears stable.

The Bay Area's population of Northern Spotted Owls is thought to be stable; however, thorough population monitoring is not available as all sites are not monitored every year.

While fecundity (reproductive success) is generally high, we lack survival data for owls, which may be more important to the overall number of birds in the population.

Current monitoring occurs on the following public lands: Point Reyes National Seashore, Golden Gate National Recreation Area, Marin Municipal Water District, Marin County Open Space District, and California State Parks (Tomales Bay, Mount Tamalpais, and Samuel P. Taylor).

Threats

Primary threat: Barred Owls pose a threat to Spotted Owls by competing for space and food. Currently, the number of Barred Owls in the Bay Area is relatively small but is predicted to increase.

Rat poisons. Spotted Owls feed upon rats; when rats have been poisoned with rodenticides used by residents and businesses, the owls become sick or die.

Sudden Oak Death changes the forest structure and plant composition, and the loss of tanoaks in particular threaten the owl’s preferred food source, the dusky-footed woodrat, which depends on the tanoak for cover and food.

Loss of forests due to urban development along national park and county open space boundaries and the threat of wildfires. Losing forests reduces feeding, roosting, and nesting habitat for Northern Spotted Owls.

Human activities, such as extended presence near Spotted Owl nest trees and noise disturbance from yard maintenance, tree trimming, and construction activities in the communities neighboring owl nesting sites, can disturb nesting owls and may prevent them from feeding their young. Community awareness of regulated protections for Spotted Owls is lacking.

Genetic isolation. The Marin County population of Northern Spotted Owls is isolated from populations to the north because of a break in forested habitat needed for dispersal. Small populations, such as those found in Marin County, are at a higher risk of local extinction.

Spotted Owl fledgling

Spotted Owl fledgling

Actions

Planning, Management, Restoration

Follow U.S. Fish and Wildlife Service guidelines for protecting Spotted Owls. Restrictions for habitat modifications around Spotted Owl territories are in effect year-round, and modifications to potential Spotted Owl habitat may require consultation with USFWS personnel.

Limit loud noises, such as motorized gardening equipment, during the nesting season (February 1st to July 9th) near Spotted Owl habitat.

Discontinue the use of rodenticides as a means to kill pests in areas with Spotted Owl habitat. Residents and business owners should consider rodent prevention and trapping instead of poisons that harm more than the rodent.

Communicate to the public the USFWS guidelines pertaining to activities such as noise disturbance and construction near Spotted Owl habitat during the nesting season (February 1st to July 9th).

Scientists

Continue and expand monitoring of Spotted Owl and Barred Owl populations on public lands. Current research is ongoing in Marin County but should be expanded to include Sonoma and Napa counties, on both public and private lands.

Public

Leave owls alone. Spotted Owls reside near many busy trails in the Bay Area, and it is not uncommon for fledgling owls to perch on the ground. If you see an owl, give it space and keep pets on leash. The parents will continue to care for a fledgling owl on the ground.

Discontinue the use of rodenticides as a means to kill pests. Residents and business owners should consider rodent prevention and trapping instead of poisons that harm more than the rodent.


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