The northern spotted owl been declining in vast parts of its range. Marin County, California, is an exception. As a result, Marin is an area of particular conservation interest. But successful conservation requires understanding the threats species face, and how those threats might change over time. So researchers recently did a vulnerability assessment of Marin's spotted owls to get answers about their exposure and sensitivity to threats.

For millennia, the hoots of northern spotted owls carried across mature forests of the Pacific Northwest. In recent decades, they started falling silent in many areas because of competition from bigger, bolder barred owls native to eastern North America. But both range-wide passive acoustic monitoring and local in-person surveys are showing that—at least for now—the spotted owls here in Marin County, California are doing remarkably well.

Each spring, National Park Service staff monitor northern spotted owl breeding activity in national and state parks in Marin County. With the 2022 breeding season now almost over, we’ve found that the local population appears stable. Marin remains the only part of the owl's historic range, which stretches north to Canada, where the population is not in severe decline.

For over 25 years, biologists from the National Park Service and several other agencies have collected spotted owl monitoring data to inform forest management that is guided by the multi-agency Northwest Forest Plan. Yet traditional field surveys for spotted owls have become less effective as their numbers have dwindled. Thus in 2021, the Northwest Forest Plan’s spotted owl monitoring design is transitioning to remote acoustic monitoring (also known as passive monitoring).

National Park Service biologists have been tracking federally threatened northern spotted owls in the forests of Point Reyes National Seashore and Golden Gate National Recreation Area for decades. But this February, biologists began to supplement traditional surveys with a new method: remote acoustic monitoring. Biologists also received a grant to use acoustic monitoring to conduct the first comprehensive inventory of invasive barred owls on park lands.

How do biologists survey endangered northern spotted owls in the forests of Marin county? Wildlife technician Taylor Ellis has some tricks up his sleeve for finding these charismatic birds. Read about his adventures as a field wildlife biologist and how he got to be where he is today.

The northern spotted owl monitoring season is winding down, and the results are nearly final as biologists complete the season's surveys. Reproduction for this year was near the average with nineteen fledglings counted from twelve successful nests. One nest failed, and ten pairs of owls did not nest this season.

Did you know that Marin County, CA, including Point Reyes National Seashore, could be essential refuges for the northern spotted owl subspecies in coming years? In forests farther north, the eastern barred owl has moved down the coast and invaded historic spotted owl territories.

Federally threatened Northern Spotted Owls are vital indicators of forest health since their survival depends on the presence of diverse, robust evergreen forest ecosystems. The National Park Service Inventory and Monitoring Program and its partners began long-term monitoring of Northern Spotted Owls in Golden Gate National Recreation Area, Muir Woods National Monument, Point Reyes National Seashore and other public lands in Marin County in 1999.

Barred owls recently expanded into the forest communities of Marin County where they may be negatively impacting the federally threatened northern spotted owl. The barred owl is an eastern species that has expanded its range westward into the Pacific Northwest and more recently southward into California. During their annual northern spotted owl surveys, National Park Service biologists in Marin also record the presence of barred owls and other potential threats.