One of the largest tidal marsh wildlife areas in California, stretching across the southern end of the Sacramento–San Joaquin Delta about 70 kilometres west of Stockton. The reserve's 9,000 hectares of tule marsh, managed wetland, and upland grassland support what is arguably the best waterbird watching in the Central Valley: greater white-fronted geese and tundra swans in winter, black-necked stilts and avocets in summer, and peregrine falcons hunting the marsh edges year-round.
The reserve is managed by the California Department of Fish and Wildlife. Access is restricted during the hunting season (typically September–January) to specific days, but the remainder of the year it is open to hikers, birdwatchers, and wildlife photographers. A long, flat access road crosses the tidal marsh and provides excellent birding from the car in winter when conditions are muddy. Take binoculars and rubber boots.