California Fauna: Clergy and Choir Stall Seat Cushions Click here for general background information on this series. Shore/Wetlands Place cursor on image to see numbers, which refer to numbers in caption below. 64. American widgeon duck pair wading near reeds; 65. great blue heron; 66. American coot afloat; 67. California clapper rail and three chicks in grass; 68. cabbage white butterfly (male) (introduced); 69. western tiger swallowtail butterfly; 70. great white herons wading (rear), and taking off from mudflat; 71. snowy egret (center, yellow feet) on shore. The ocean shore is home to birds of surf and cliffs. The adjacent San Francisco Bay is actually a vast tidal estuary, the largest on the west coast of North America. Only fragments remain of the extensive marshes and wetlands that once lined its shores. These fragments are a major biennial resting and feeding area for migrating birds along the Pacific flyway, and the skies of the Bay were once darkened by huge flocks. Most of the original species still visit, in greatly reduced numbers. The Canada goose and mallard duck are two of the most familiar visitors, along with pelicans, herons, egrets and gulls. Smaller shore birds still visit in large numbers; phalaropes, willets and sanderlings, avocets, turnstones, plovers and godwits can still put on breathtaking shows of coordinated flight. The endangered California least tern is sometimes seen. Many of the birdslisted were impacted by the 2007 oil spill in San Francisco Bay. The muddy shores are bursting with isopods, clams and oysters; a feast for any visiting bird. Quieter reedy sloughs are the haunt of the endangered California clapper rail and the endangered salt marsh harvest mouse. The Xerces Blue butterfly is extinct.