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� � � California clapper rail (Rallus longirostris obso/etus) in the Redwood Shores Area* Perennial inhabitant of greater San Francisco Bay tidal marshes. Federal endangered species: 35 Federal Regi.rter 16047 —16048 (13 October 1970). California endangered species: Tide 14, Califorrria Code of Regulationr, � G70.5 (27 June 1971). Description The California clapper rail, a secretive, "henlike" waterbird, is one of the largest rails, measuring approximately 13 to 19 inches from bill to tail and weighing about 250 to 300 grams. The bud has a long slighdy downward-curving orange bill, a cinnamon-buff colored breast, olive-brown upper parts, black and white barred flanks, and white undertail coverts. The brown back feathers are edged with gra��. Males are slighdy larger than the females. The young have a pale bill and darl: plumage. Distribution California clapper rail populations are currendy limited to San Francisco Bay, San Pablo Bay, Suisun Bay, and the tidal marshes associated with estuarine sloughs that drain into these bays. HIStOry. Historically, California clapper rails ranged within coastal tidal marshes from Humboldt Bay� southward to Elkhorn Slough and Morro Bay and from the estuarine mazshes of San Francisco and San Pablo bays to the Carquinez Strait (LSA, 2004). The highest densiry of clapper rails historicall�� was found in south San Francisco Bay. In 1880, the California clapper rail was classified as a distinct species, reclassified as a clapper rail population in 1926, and recognized as one of numerous clapper rail subspecies in 1977 (Erlich et al., 1992). Before about 1900, "thousands" of clapper rails were reportedly killed by hunters each week (Thelander, 1994). The Migratory Bird Treatv �ct of 1918 prohibited clapper rail hunting and its numbers rebounded. However, destruction of much of the salt marsh habitat for the bird caused its numbers to dwindle precariousl�•. Of the 193,800 acres of tidal marsh bordering San Francisco Bay in 1850, only slighdy more than 30,000 acres remain. When listed as endangered in 1970 (U.S.) and 1971 (CA), the California clapper rail population was estimated at 4,200 to 6,000 birds; the all-rime historical low is about 500 individuals, with about 300 of these in the south part of San Francisco Bay. The population has subsequendy rebounded (see below) as a result of predator management acrivities. The south San Francisco Bay population is now estunated to be between 500 and 600 birds, with some 200 to 300 pairs occurring in the north part of San Francisco Bay. L.ikel}> causation of the duninution of the population is a combination of the fragmentation of the clapper rail's habitat and increased predation, described in more detail below (CDVi�R-IEP). * PREPARED BZ' I�iS. TUNSTr1LL LANG, JD, REA, OF THE HUFFMAN-BROADWAY GROUP, INC. PAG� 1 OI� 41