This IBA is located on the north side of San Pablo Bay, the northernmost extension of San Francisco Bay, and encompasses the low-lying areas from the town of San Rafael north and east, taking in the Petaluma River Marshes (north to Novato and Petaluma); Sonoma Creek; and the Napa River Marshes to Mare Island (adjacent to the City of Vallejo). Included are the well-known wetlands of Mare, Knight, Coon, Russ and Bull Island; and White, South, Dutchman's and Fagan sloughs. These marshes, bounded on the north by the foothills of the Northern Coast Range that define the Sonoma and Napa Valleys, are bisected into a coastal and inland section by Highway 37.

The habitats here are a mosaic of wetlands dominated by diked former wetlands that are flooded during storm events and high tides (many of which are used for agriculture); and shallow, former salt evaporation ponds alternately filled and dried (some greatly exceeding the salinity of the ocean). Fingers of tidal saltmarsh weave throughout the landscape, widening along the edge of the bay and along the Petaluma River. Smaller areas of freshwater wetlands (also created and defined by dikes) are interspersed throughout, and a broad band of tidally-exposed mudflats at the edge of the bay extends across the length of the Important Bird Area.

Much of the land on the south side of Highway 37 is federally managed as the San Pablo Bay National Wildlife Refuge, and that on the north side is protected by the State of California as Petaluma Marsh Wildlife Area and Napa-Sonoma Marsh Wildlife Area. These reserves, along with several private duck hunting clubs, ensure that much of the area is managed as open space. Additionally, other groups are working to protect and enhance habitat in the San Pablo Bay Wetlands. Marin Audubon Society has purchased strategic parcels for conservation and is activetly restoring habitat by returning tidal flows to formerly diked baylands (e.g. Petaluma Marsh Expansion and Bahia).

Ornithological Summary

The San Pablo Bay Wetlands represent one of most important tidal estuaries in the state, and support essentially the entire range of the endemic San Pablo Song Sparrow, around half the global population of California Black Rail, the race confined to the western U.S. and adjacent Baja California, Mexico (Evens and Nur, in press). Tidal wetlands in the Bahia area support largest Clapper Rail population in the north Bay (15-21 pairs, 2005 census Jules Evens). San Pablo Bay Wetlands are of major regional importance for other marsh species that require vast areas of open space, including breeding Short-eared Owl. Yellow-headed Blackbird has bred in the past (Burridge 1995) and may continue to do so locally. Exceptionally large numbers of migrant and wintering waterfowl occur here, particularly Canvasback (the original reason for the designation of the San Pablo Bay NWR). Roughly 65% of the state's wintering Canvasback occur on San Francisco Bay, and about 80% of the this population occurs within San Pablo Bay (Accurso 1992). Other waterfowl that occur in exceptional numbers include Northern Shoveler, Ruddy Duck, Bufflehead, and Greater Scaup. The Napa wastewater facility regulary hosts 5000-10,000 Northern Shovelers during the September-November season. Thousands of shorebirds utilize the exposed mudflats for feeding and roost in the salt ponds during high tide, when they are joined by tens of thousands more from other areas of the Bay (Gary Page, via email). The salt ponds also support breeding terns, Double-crested Cormorant and a handful of nesting Snowy Plover. Finally, the upland areas on the northern edge of this Important Bird Area are becoming increasingly important to Loggerhead Shrike and other grassland species as they are pushed toward the bay by urban development inland. Yellow-headed blackbirds were found breeding in Napa county part of the Napa Marsh in 1991 and 1992 (Robin Leong).

Help us learn more about the birds at this IBA! Enter your birding data online at Calfornia eBird! (http://ebird.org/california/)

Conservation Issues

The conservation priorities within this Important Bird Area are threefold, as identified by the Goals Project (1999). First, lands acquisition is urgently needed of both wetland and upland "buffer" habitat, particularly around rapidly-urbanizing areas of eastern Marin County and Vallejo. A proposal to create a "Marin Baylands National Wildlife Refuge" on the southwestern shore of San Pablo Bay was put forth in 2000 but is currently on-hold. Second, large-scale reclamation of former salt ponds to a more natural state would help realize the potential of this Important Bird Area for the original wetland bird communities. Finally, aggressive exotic species removal must be undertaken to secure the health of already-protected lands that are being overrun with weeds (e.g. Pepperweed and Stinkwort) and mammalian invaders (e.g. Red Fox, feral cats). Unleashed dogs are a particular problem in the Huichica Creek Unit of the Napa-Sonoma Marsh W.A., the same area that supports nesting waterfowl, Snowy Plovers and wintering Burrowing Owls (Robin Leong).

Ownership

Much of the land on the south side of Highway 37 is federally managed as the San Pablo Bay NWR, and that on the north side is protected by the State of California as Petaluma Marsh Wildlife Area and Napa-Sonoma Marsh Wildlife Area. These reserves, along with several private duck hunting clubs, ensure that much of the area is managed as open space.

Habitat

This IBA includes the Petaluma River Marshes; Sonoma Creek; and the Napa River Marshes. Included are the well-known wetlands of Mare, Knight, Coon, Russ and Bull Isl.; and White, South, Dutchman?s and Fagan sloughs. The habitats here are a mosaic of wetlands dominated by diked former wetlands that are flooded during storm events and high tides (many of which are used for agriculture); and shallow, former salt evaporation ponds alternately filled and dried (some greatly exceeding the salinity of the ocean). Fingers of tidal saltmarsh weave throughout the landscape, widening along the edge of the bay and along the Petaluma River. Smaller areas of freshwater wetlands (also created and defined by dikes) are interspersed throughout, and a broad band of tidally-exposed mudflats at the edge of the bay extends across the length of the IBA.

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