RECOVERY STRATEGIES FOR THE CALIFORNIA CLAPPER RAIL (RALLUS-LONGIROSTRIS OBSOLETUS) IN THE HEAVILY-URBANIZED SAN-FRANCISCO ESTUARINE ECOSYSTEM

The California clapper rail (Rallus longirostris obsoletus), a Federal - and State-listed endangered marsh bird, has a geographic range restr icted to one of the most heavily-urbanized estuaries in the world. The rail population has long been in a state of decline, although the exa ct contribution of each of the many contributing causes remains unclea r. The rail is one of the key targets of emerging plans to conserve an d restore tidal marshlands, Reduction of tidal marsh habitat, estimate d at 85-95%, has been the major historical cause of rail decline. incr eased predation intensity may be the more important present problem, b ecause habitat fragmentation and alteration coupled with the invasion of the red fox have made the remaining populations more vulnerable to predators, Population viability analysis shows that adult survivorship is the key demographic variable; reversals in population fate occur o ver a narrow range of ecologically realistic values. Analysis of habit at requirements and population dynamics of the clapper rail in the San Francisco Estuary shows that decreased within-marsh habitat quality, particularly reduction of tidal flows and alteration of drainage, is a n important barrier to population recovery. Management and restoration activities should emphasize the development of well-channelized high tidal marsh, because this is the key requirement of rail habitat, Deve loping effective restoration programs depends upon having information that field research will not provide. The effect of spatial pattern of reserves requires accurate estimation of the effects of predation and inter-marsh movement, both of which are practically impossible to mea sure adequately. It will be necessary to develop and use simulation mo dels that can be applied to geographic data to accomplish this task. ( C) 1997 Elsevier Science B.V.