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III. Environmental Setting, Impacts,and Mitigations F. Vegetation and Wildlife Swainson's hawk (Buteo swainsoni)is a State-listed threatened species that has suffered a minimum estimated 91 percent population decline over the past century. This is primarily a result of destruction of 98 percent of the riparian habitat in California, as well as conversion of foraging habitat to non-suitable cover types(Estep, 1989;Bloom, 1980). This species breeds in Canada and the western United States and winters in South America. Swainson's hawks breed mostly in California,primarily in the southern Sacramento and northern San Joaquin Valleys(85 percent of the Central Valley population)from April through mid- August. This hawk typically nests in large trees in woodlands and riparian forests in the Central Valley. Nests are also typically located adjacent to grasslands or agricultural lands which provide a vegetative cover type,such as alfalfa,beets, or tomatoes,that is compatible with the foraging requirements of the species. Other preferred agricultural habitats include disced field, fallow field,dry-land pasture,and irrigated pasture. Nests are occasionally used perennially (Estee, 1989; Bloom, 1980;CDFG, 1991; CDFG, 1992). The CNDDB contains seven recent nesting records(i.e., 1990)of this species within a five mile radius of the proposed project site,including a Swainson's hawk nest record approximately 1.5 miles northwest of the study area near the junction of Arch Road and Frontier Way(CDFG, 1993). During ESA's site visits,a pair of Swainson's hawks was observed nesting in a valley oak adjacent to Austin Road on the Brocchini property on April 4, 1991 (see Figure III.F.1). During subsequent field work,no additional nesting of this species was observed,although a total of thirteen potential raptor nests were identified in on-site trees(see Figure III.F.1). Additionally, Swainson's hawks were observed foraging over the Brocchini property and adjacent lands to the east on April 4, 1991,July 2, 1992,and March 19, 1993. Thus,this species has been observed both nesting and foraging on-site. Mountain plover(Charadrius montanus)winters in grasslands and agricultural lands of the Sacramento and San Joaquin Valleys,from.Sutter and Yuba Counties southward,between September and March. This species forages on the ground for large insects in open lands with low, sparse vegetation(Zeiner, 1990). Although the CNDDB contains no records of this species from within the vicinity of the site,the project area(Brocchini property-when fallow in the winter)provides potentially suitable winter foraging habitat for this species. The dense cover of weedy species on the CYA property may preclude foraging of this species on this site. Northern harrier(Circus cyaneus)is a yearlong resident of the Central Valley and Sierra Nevada. This species inhabits freshwater and saltwater emergent wetlands and grassland III.F.17