Tidally-Induced Limits to California Clapper Rail Ecology in San Francisco Bay Salt Marshes

The state and federally endangered California clapper rail (Rallus longirostris obsoletus) has declined in abundance and been reduced in range and now occupies fragmented intertidal saltmarsh only within San Francisco Bay. Historically extensive salt marsh habitats existed in San Francisco Bay and today, remnants are largely restricted to the water’s edge with dikes and levees separating marshland from modified habitats unsuitable for clapper rails. Clapper rail population abundance has roughly tracked a series of positive and negative impacts including market hunting at the turn of the 20th century, widespread habitat reduction and fragmentation, and invasive species introduction and eradication programs. Despite these changes, rail populations have been subject to the ebb and flow of the tides, which regularly inundate salt marsh habitats. The influence that tides have on vertebrate species living in intertidal saltmarsh should be substantial, but the relationship between tide and California clapperrails is poorly understood. This research identified important ways in which tides influenced demographic processes, space use, and resource selection in California clapper rails.