Santa Clara River at the Santa Clara River Weir Field - Least Bell’s Vireo Survey, Ventura County, California
Project Name: Santa Clara River at the Santa Clara River Weir Field - Least Bell’s Vireo Survey, Ventura County, California Services: Breeding Bird Survey Client: Ventura County Watershed Protection District
Padre biologists and a subconsultant to Padre conducted a study of territory location and size of the State and Federally Endangered least Bell’s vireo (Vireo bellii pusillus) (vireo). The study was conducted on an approximately 4,000 feet reach of the Santa Clara River in Ventura County, California. The study objectives as recommended by the U.S. Fish and Wildlife Service and the Ventura County Watershed Protection District were: a) to establish whether or not vireos were present within 1,000 feet of a flood improvement project site area (study area), b) if vireos were present, to determine what portion of their territory was within the project study area and buffer and c) to identify what their nesting stage was. Five surveys were conducted at the study area between June 7 and July 26, 2010 at approximately 10-day intervals. The study spanned the typical incubation, nestling and fledgling periods. The biologists used a standard technique of spot mapping to accomplish the study objectives. During each survey, biologists walked the levee, trails, and dirt roads adjacent to and within the territories identified by Padre. Suitable habitat up to 1,000 feet from these study areas was also surveyed. At each site, the biologists covered between 3.3 and 8.6 acres for a total of 33 acres. They attempted to detect vocalizing vireos, and marked the approximate location of each observation on an aerial photograph of the study area. Then they followed the vireo for up to 30 minutes, noting all locations the bird transited, foraged, perched, and sang. Nesting behaviors such as bringing nesting material and food items to nests and young and the presence of begging young were noted. To the extent possible, observations were limited to existing trails and bare areas within the riverbed in order to minimize impacts to the vireos. Each location a vireo was detected was mapped and digitized by Padre, then a map showing the points and an estimate of the territory size was created and a report produced.