The San Francisco Bay estuary is highly urbanized, and as a result roughly 80% of its historic tidal marshes have been lost (Goals Project 1999). The California Clapper Rail (Rallus longirostris obsoletus), now restricted to the San Francisco Bay estuary (Gill 1979), is listed as endangered by both the U.S. Fish and Wildlife Service (1973) and California Department of Fish Game (Leach et al. 1976). Secretive birds found in the dense vegetation of tidal salt marshes, California Clapper Rails forage on crustaceans and other salt-marsh invertebrates (Eddleman and Conway 1998). California Clapper Rails usually lay eight eggs and often resent after failed nesting attempts (Eddleman and Conway 1998). The sexes are similar in plumage, but males tend to be larger. Recent estimates of the population range between 1200 and 1500 individuals (Harvey 1988, Garcia 1995, Albertson and Evens 2000). Because California Clapper Rails are difficult to observe little is known about their dispersal and breeding behavior. Radio telemetry on individual birds, however, provides a valuable tool for investigating these and other aspects of California Clapper Rail ecology.