Checking the Vital Indicators:
The Northern Spotted Owl is a quiet and reclusive bird. Prior to the 1990’s, little was known about their lives in the National Park sites within Marin County. Only a few pairs were thought to live in the area. In order to successfully manage the parks it is crucial that the National Park Service know all it can about this important indicator species.
National Park Service biologists began conducting surveys to determine Northern Spotted Owl distribution and habitat use in Muir Woods National Monument, Golden Gate National Recreation Area and Point Reyes National Seashore in Marin County, California in 1993. The survey area gradually expanded with the help of PRBO Conservation Science, project volunteers, and land managers to include Samuel P. Taylor, Tomales Bay and Mount Tamalpais State Parks, as well as Marin Municipal Water District and Marin County Open Space District lands.
Between 1997 and 2005, 197 different Spotted owl nests and over 375 fledglings were located during surveys in Marin County. Several instances were documented in which spotted owl pairs reused the same nest in different years. The owls fared better in some years than others – more than 70% of the pairs attempted nesting in 2001, with nearly all nests producing young. By comparison, in 1999, only 48% of Spotted owls nested with about half of those nests being successful. NPS biologists documented the first non-nesting season in 2007, perhaps a result of climatic triggers that affected prey availability.
Visit the National Park Service's Inventory and Monitoring Program to learn more about monitoring objectives, protocols and research on Northern Spotted Owls.