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It follows from this observation that if cattle were removed from the grassland community and a dense grass mat ground cover was allowed to form, rodent production on the site would dramatically increase and with it, a larger number of predator species. A strong rodent prey base forms the primary consumer link of the food chain upon which the hawk and owl species previously mentioned, plus mammalian carnivores such as coyote(Canis latrans),gray fox(Urocyon cinereoargenteus),badger(Taxidae taxus), and raccoon (Procyon lotor), depend. All of these species were observed either directly or indirectly (tracks, scat, etc.)during the course of the study. Perhaps the most interesting wild mammal observation made during the survey was that of a natal den of coyotes located at the southern edge of Brovelli Woods. An adult pair raised four pups at this location while apparently foraging on and adjacent to the project site. Endangered/Threatened Species and Habitat Plants None of the species reported by Muick, 1989,or those observed during the spring 1992 survey are listed as endangered or threatened by the California Department of Fish and Game or in the category lists 1 and 2 of the California Native Plant Society. This includes species observed in the vernal pools,a habitat which often contains threatened or endangered plants. Wildlife The only species that breeds on the project site and is protected by law under the 1984 California Endangered Species Act is the Swainson's hawk. Because its presence has a major bearing on assessing the impacts which could result from construction of the proposed Buckeye Ranch project, a sound understanding of its biology and the current guidelines which govern its protection is necessary for a thorough evaluation of this situation. The Swainson's hawk is a medium-size buteo or soaring hawk with long,pointed wings and a square tail. Unlike most hawks, it exhibits several color phases ranging from light through rufous to very dark plumage. It is also unique among California raptors in that it migrates to the Central Valley from South America in late March and early April to nest and raise its young,and then in late August and September migrates back to Argentina and other neighboring countries for the fall and winter (U.S. Fish and Wildlife Service, 1986). Many factors have been postulated as possible causes for the declining population of Swainson's hawks in California. These include incompatible agricultural crops for the production and/or capture of prey (Bloom, 1980),grazing pressure(Detrich, 1986),predation on eggs and nestlings(U.S.Fish and Wildlife Service, 1986),depredation by humans on the wintering grounds (Bloom, 1980),pesticide use (Bloom, 1980;Detrich, 1986),the loss of habitat through land use conversions(California Department of Fish and Game, 1990),and direct competition with the more aggressive and abundant red-tailed hawk(Craighead and Craighead, 1956). Although the exact combination of factors responsible for its decline may never be known, there is no debate concerning the fact that Swainson's hawk numbers have dropped drastically during the past century in California. Historically,this state's Swainson's hawk population may have exceeded 17,000breeding pairs (Bloom, 1980). However,current population estimates average about 550 pairs for the entire state and 280 pairs for the Central Valley (California Department of Fish and Game, 1990). 18