Northern Spotted Owl Inventory on Federal Lands in Marin County, California: 2006 Report

Jensen, Heather; Adams, Dawn; Merkle, William

This report details the results of the tenth year of the Northern Spotted Owl (Strix occidentalis caurina) Monitoring Program in Marin County, California. The goal of the 2006 monitoring effort was to complete an inventory of suitable Spotted Owl habitat on federally legislated lands within Marin County. The intended audience of this report includes partners in our monitoring program as well as appropriate agencies at the county, state, and federal levels. The report provides an overview of the 2006 Northern Spotted Owl inventory on federal lands and summarizes the results of the data collected during the field season. In 2006, the monitoring program completed an inventory of suitable Spotted Owl habitat within the legislative boundaries of Point Reyes National Seashore (PORE), Golden Gate National Recreation Area (GOGA), and Muir Woods National Monument (MUWO). The 2006 inventory study is intended to part of the ongoing, long-term monitoring program initiated in 1999, succeeding the initial Spotted Owl inventory effort completed during 1997-1998 breeding seasons. During the breeding season, we inventoried the study area for Spotted Owl presence using a combination of known activity site monitoring and standard inventory methods. The goal was to collect occupancy information for all Spotted Owls detected including current owl activity centers, owl occupancy status, age of owl, sex of owl, and if applicable, band identification. Due to the increased workload of surveying inventory areas in addition to known sites, reproductive information was collected opportunistically in 2006 and therefore will not be included in this report. During the 2006 breeding season, Marin County’s survey teams completed 298 surveys to a total of 43 known Spotted Owl territories or “sites” and 22 inventory areas. Additionally, 19 known Spotted Owl territories situated outside the perimeter of federal lands were monitored based on resource management needs. For this report, only information pertaining to the 65 inventory areas and monitoring sites was included. The 2006 official status of each Spotted Owl territory or inventory area was determined using the USFWS “Protocol For Surveying Proposed Management Activities That May Impact Northern Spotted Owls” (USFWS 1992). At a minimum, a single Spotted Owl response was detected at 59 of the 65 areas monitored for occupancy and inventory purposes in 2006. Pairs of Spotted Owls occupied 43 of the 65 (66%) areas. Eight of the 65 areas (12%) were confirmed to resident single status. At an additional eight areas were categorized as single unknown status. Single unknown status indicates that a Spotted Owl response was detected, but despite repeated survey efforts the Spotted Owl status could not be confirmed to USFWS protocol. Areas where Spotted Owls were not detected composed 10% of the survey effort.