Wednesday, February 7, 2007


Nowhere along the Pacific coast is the problem as acute as in San Francisco Bay, where several national wildlife refuges spotted along the perimeter of the intensely urban shoreline face problems from feral cats and the non-native eastern red fox, an alien species introduced to California in the last century. Locally these predators threaten at least three imperiled ground-nesting birds and an endangered mammal -- the California clapper rail, the California least tern, the western snowy plover, and the salt marsh harvest mouse.
Wildlife biologist Joy Albertson of the Don Edwards San Francisco Bay National Wildlife Refuge noted the declines in clapper rail populations due to cats and foxes as she studied predators in south San Francisco Bay during academic investigations in the early 1990's. The clapper rail, a secretive denizen of the salt marsh, is found nowhere else in the world except San Francisco Bay tidal marshes. One clapper rail, fitted with a radio telemetry device as part of the research study, was, itself, killed by a feral cat, and biologists continue to observe cats frequently stalking rails in area marshes.
Sightings in 1991 in a marsh complex managed cooperatively with the City of Palo Alto detected either one or two cats in the marsh or along levees in six of 10 nighttime surveys; by 1992, those numbers had jumped -- up to five cats in eight of 11 evening surveys. In four other marshes more distant from residential neighborhoods, however, the number of cats was lower.
Says Albertson, "Feral cats are a serious and increasing threat to endangered species in the Bay area and in other urban areas where sensitive wildlife habitat is close to residential housing and pets."

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