Tomales Bay is a narrow, 15-mile-long tidal estuary along the San Andreas Fault on the northeast side of Pt. Reyes. It is situated between Bodega Bay in the north and Bolinas Lagoon in the south, to the east of Drake's Estero - all critical estuaries of the Pt. Reyes region. Most of the tidal marsh and mudflat habitat forms at the south end, near the village of Inverness, with additional habitat at the mouth of Walker Creek along the northeast shore. The south side of the bay grades into an extensive freshwater marsh/riparian corridor (including Olema Marsh), surrounded by humid coniferous forest.

Tomales Bays' importance has been recognized by the international Ramsar Convention, which designated the site as a "Wetland of International Significance." Tomales Bay supports more than 50 species of waterbirds, numbering more than 20,000 individuals. Its extensive eelgrass beds attract more than 1% of the world's populations of Black Brant, while the bay's mudflats are visited by more than 1% of the world's populations of Dunlin and Western Sandpiper. The bay supports 10% of California's Coho Salmon and its a major spawning ground for Pacific herring. Tomales Bay supports 13 threatened or endangered species.

About 1000 acres of wetlands and adjacent uplands here is managed by the State of California (Tomales Bay State Park, Tomales Bay Ecological Reserve), which continues to add acreage with the help of the non-profit Trust for Public Land. The Important Bird Area has been intensively studied by both Audubon Canyon Ranch (through the Cypress Grove Research Station) and by PRBO.

Beginning in 2007, the National Park Service's Giacomini Wetland Restoration Project has returned more than 550 acres of formerly diked wetlands at the southern edge of Tomales Bay to tidal action. This represents a 50% increase in tidal marsh acreage in Tomales Bay and increasing value to the habitat as tidal marsh and riparian vegetation fills in the formerly diked baylands.

Ornithological Summary

Of all the Pt. Reyes wetlands, Tomales Bay consistently supports the highest numbers of wintering and migrant waterbirds, including loons, grebes, cormorants, geese, diving and dabbling ducks and shorebirds. Up to 20,000 shorebirds spending the winter (Shuford et al. 1989). Surveys have documented exceptionally large numbers of Bufflehead and Brant, which represent 12% and 31%, respectively, of statewide wintering populations (Kelly and Tappen 1998). This site supports California's largest population of Black Rail on the immediate coast (though much larger numbers occur within San Francisco Bay), and Clapper Rail, though no breeding has been confirmed, and wintering Yellow Rail, a species nearly extirpated from California. Least Bittern maintains one of its only Bay Area colonies at Olema Marsh.

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Conservation Issues

Because this site is so well protected, no major threats such as development have been identified. However, Kelly and Tappen (1998) have pointed to potential disturbance of waterfowl by recreational and fishing boat (including kayaks) within the bay. Recently, high levels of mercury have been detected in the bay.

Ownership

About 1000 acres of wetlands and adjacent uplands here is managed by the State of California (Tomales Bay State Park, Tomales Bay Ecological Reserve) and another 500+ acres is managed by the National Park Service. The IBA has been intensively studied by both Audubon Canyon Ranch (through the Cypress Grove Research Station) and by PRBO.

Habitat

Tomales Bay is a narrow, 15-mile-long tidal estuary along the San Andreas Fault on the northeast side of Pt. Reyes. Most of the tidal marsh and mudflat habitat forms at the south end, near the village of Inverness, with additional habitat at the mouth of Walker Ck. along the northeast shore. The south side of the bay grades into an extensive freshwater marsh/riparian corridor (incl. Olema Marsh), surrounded by humid coniferous forest.

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