Northern Spotted Owl
The northern spotted owl is found throughout Marin County including 
the forests of Point Reyes National Seashore, Golden Gate National Recreational Area, and Muir Woods National Monument. The species has been listed as threatened since 1990. This legal designation requires the NPS to monitor the long-term status and trends of the population and maintain stable or increasing populations of spotted owls.
The NPS Inventory and Monitoring program has been monitoring the spotted owls for 9 years now. The information collected contributes to region and range-wide monitoring programs and park management activities.The Marin County northern spotted owl population is subject to unique threats present in this portion of the range including: 1) urban development along open space boundaries, 2) disturbance due to intense recreational pressures, 3) potential for catastrophic wildfires along the urban/wildland interface, 4) possible genetic isolation and 5) emergent biological threats (Sudden Oak Death, West Nile Virus, and the continued range expansion of the Barred Owl). More information on biological threats to the spotted owl can viewed with the northern spotted owl conceptual model.
Monitoring Objectives
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Monitor changes in northern spotted owl abundance and reproductive success at known owl activity sites within the NPS legislated boundaries of Marin County , California .
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Determine the long-term changes of nest site characteristics (e.g. tree species selected for nest sites, vegetation community selected for nest sites) at northern spotted owl known activity sites in order to evaluate habitat selection.
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Monitor suitable habitats every 5-10 years in order to identify population expansion of target species and incorporate them into annual abundance estimates
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Reports and Resources
- 2-page northern spotted owl Executive Briefing (PDF)
- New! Interactive northern spotted owl Model
- Quick Time Video of a female spotted owl feeding its young. (Quick Time 1315KB)
- 2007 Annual Report
- 2006 Annual Report
- 2005 Annual Report
- 2-page barred owl Executive Briefing (PDF, updated 02/2009)
Contact Information
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Monitoring Protocol
- Northern spotted owl Monitoring is conducted using the US Forest Service Protocol ( Forsman 1995) modified for Marin County (Fehring et al 2000). Currently, surveys take place between March and August in Marin County .
- Annual monitoring of a subset of known nest and roost sites (activity centers) is used to determine occupancy, pair identification (bands) and reproductive status.
- Inventories of suitable habitats within the project area are conducted every 5-10 years in order to identify potential spotted owl population expansion.
- Monitoring will be partially supported by Point Reyes National Seashore Association. Each year, 15 to 30 additional owl activity sites are surveyed throughout Marin County outside of the NPS lands. The monitoring at these sites is supported by PRBO Conservation Science, Marin Municipal Water District and Marin County Open Space District and serves to expand the probability of resighting banded owls that have relocated out of the NPS study area, as well as detecting any Barred Owls in the area.
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