The northern Central Valley, defined by the Sacramento River watershed, contains some of the most important waterfowl habitat in the Pacific Flyway. Historically, much of the Sacramento River floodplain was a mixture of seasonally flooded basins surrounded by riparian areas and grasslands. The Butte, Colusa, Natomas, American, Sutter and Yolo Basins are still important waterfowl areas, but wetlands are now flooded through controlled water deliveries. Some of the most important public and private waterfowl areas, as well as some of the most productive rice fields, in California are located in these historic wetland basins.
Waterfowl use the Sacramento Valley primarily as a wintering ground. Between 1 and 3 million ducks, geese and swans use the Sacramento Valley at any given time during the winter. The valley's seasonal wetlands are also used by waterfowl as breeding grounds, although in much fewer numbers than during the winter. Mallards are the most common nesters, followed by wood ducks, gadwalls, cinnamon teal and a mixture of other species.
Ducks Unlimited's conservation projects in the Sacramento Valley Region focus on providing habitat management infrastructure improvements to both private and public waterfowl areas, restoring seasonal wetlands, securing water supplies for wildlife areas and protecting important agricultural areas from urban development.