Mature forests, a plentiful food supply, and the mild climate of parks in this network provide ideal habitat for the northern spotted owl. Once plentiful in late-succession forests throughout the west, loss of habitat led to this owl's listing as a federally threatened species in 1990. A closely related species, the barred owl, began occupying this region in 2002, and may threaten northern spotted owls through competition and interbreeding.
Northern spotted owls are considered to be an indicator species that helps gauge the ecological health of forest habitat. Through long-term monitoring of site occupancy and reproduction, biologists study and monitor owls in Bay Area national parks and on nearby public lands. Monitoring data helps land managers to minimize disturbance to nest sites, learn how threats affect existing populations, and plan future conservation efforts.