Bay at Pescadero Creek was made unsuitable for 

 habitat by the closing of its connection to the 

 sea by a sand bar; at Watsonville Slough, habitat 

 was destroyed by a housing development with 

 associated pollution. Some uninhabited marshes 

 in north San Francisco Bay are contaminated 

 with oil scum (Gould 1973). 



PRIORITY INDEX 



16 



DESCRIPTION 



R. I. obsoletus is a chicken-sized bird; grayish 

 brown above with light ocraceous buff or tawney 

 breast, flanks of grayish brown barred with white, 

 and a white patch under the short, upcocked tail. 

 Two color phases occur, one more brownish, the 

 other more olivaceous. The iris is reddish orange; 

 the bUl is orange yellow at the base with the rest 

 brown; the legs and feet are brownish gray. Downy 

 young are jet black with greenish olive above. The 

 legs are long (57 mm); toes 51 mm; bill 59 mm. It 

 is a strong runner, but a weak flyer (Ridgway and 

 Friedmann 1941, Ripley 1977). It differs from R. 

 I. levipes principally in the more grayish (less 

 brownish) edgings and blacker centers of back 

 feathers and less reddish underparts (Van Rossem 

 1929). Adults weigh about 330 g (Linsdale 1936). 



RANGE 



The California clapper rail was formerly found 

 in coastal marshes at Humboldt Bay (Brooks 

 1940), Tomales Bay, and Bolinas Lagoon in Marin 

 County (Gill 1972), Monterey Bay at Watsonville 

 and Elkhom Sloughs (Silliman 1915, Gill 1972, 

 Gould 1973), and probably Morro Bay (Brooks 

 1940). In the San Francisco Bay area, major popu- 

 lations centered in salt marshes bordering the 

 southern arm in Alameda, Santa Clara, and San 

 Mateo Counties and smaller populations occurred 

 in the northern part of the bay and San Pablo Bay 

 in Marin, Sonoma, Napa, Contra Costa, and ex- 

 treme western Solano Counties (Grinnell et dl. 

 1918, Bent 1926, Grinnell and Wythe 1927, 

 DeGroot 1927, Grinnell and Miller 1944). 



At present, the largest populations continue 

 to be in southern San Francisco Bay, with smaller 

 numbers in the northern San Francisco and San 

 Pablo Bay marshes, at Corte Madera Marsh near 

 the mouth of Gallinas Creek, Petaluma Marsh, 



marsh south of San Pablo Creek; marsh north of 

 toll plaza of the San Francisco - Oakland Bay 

 Bridge, and at Tubbs Island. They are apparently 

 gone from all coastal marshes on Monterey Bay 

 except Elkhom Slough (GUI 1972, Gould 1973, 

 Varoujean 1972, Wilbur and Tomlinson 1976). 

 Although apparently nonmigratory (Wilbur 

 and Tomlinson 1976), the rails are known to 

 wander away from salt marshes in autumn (Lins- 

 dale 1936; Orr 1939) even to Farallon Islands 

 (Bryant 1888). 



RANGE MAP 



The range map on the following page shows 

 both past and present distribution. 



STATES/COUNTIES 



California: Alameda, Santa Clara, San Mateo, 

 Marin, Sonoma, Napa, Contra Costa, 

 Solano, Humboldt, Monterey, San 

 Luis Obispo. 



HABITAT 



R. I. obsoletus inhabits saltwater marshes 

 traversed by tidal sloughs, usually associated with 

 abundant growths of pickleweed (Salicornia) 

 (Grinnell and Miller 1944). GiU (1972) classified 

 marsh habitat in southern San Francisco Bay into 

 primary habitat or pure stands of cord grass 

 {Spartina foliosa) with 0.84 to 1.08 rails per ha, 

 and secondary habitat of pure stands of pickle- 

 weed or mixtures of cordgrass, pickleweed, and 

 other marsh vegetation with 0.13 to 0.17 rails 

 per ha. In southern San Francisco Bay, Zucca 

 (1954) found 69 of 87 nests (79%) in pure stands 

 of cordgrass, 10 in bases of gumplant {Grindelia) 

 bushes, 6 in pickleweed and 2 in mixed cord grass 

 and pickleweed. Wilbur and Tomlinson (1976) 

 note that early writers usually described nests as 

 occurring in pickleweed or at the base of gum- 

 weed plants, but later studies showed regular use 

 of cordgrass as a nest site. Zucca (1954) found 

 that time of nesting and tidal conditions deter- 

 mine, in part, the type of vegetation used for nest- 

 ing, with early nests placed in gumweed before 

 cordgrass growth occurs and nests placed in pickle- 

 weed, which grows at slightly higher elevations 

 than gumweed or cordgrass, when nesting is inter- 

 rupted by tidal flooding. 



Moffitt (1941) points out that rails are 



