Knoxville Wildlife Area is approximately 21,500 acres and is part of the 300,000 acre Blue Ridge/Berryessa Natural Area in Napa, Lake, Colusa, and Yolo Counties. The terrain is rugged in Knoxville, with elevations ranging from 1,000 feet to 2,200 feet. It is one of the few sites in California that protects unusual serpentine habitats. Serpentine soils are high in toxic metals, and low in plant nutrients, so the assemblages of plants that can tolerate them are unusual. This habitat supports a wide array of songbirds, mammals, amphibians, and reptiles. Some species possibly seen include black bears, bobcats, belted kingfishers, northern dippers, mergansers, golden eagles, and native fish species such as the California roach and the Sacramento pikeminnow.