Central Valley of California
California's Central Valley and coastal habitats support up to 60 percent of the Pacific Flyway's wintering waterfowl, including nearly 6 million ducks and 1 million geese. Roughly 40 percent of this continent's pintails winter in the Central Valley. Significant numbers of American wigeon, mallards, green-winged teal, shovelers and tundra swans as well as nearly the entire continental population of tule white-fronted geese also winter here.
Conservation planners use "waterfowl use days" as a measure of a landscape's capacity to support migrating and wintering waterfowl. Specifically, a waterfowl use day is defined as the energy needed by one bird for a day during the nonbreeding period. The Central Valley provides close to 1 billion waterfowl use days from the time ducks and geese arrive in fall to their departure in spring. This is truly remarkable given that 95 percent of the Central Valley's historical wetlands have been lost. As in other regions, waterfowl that winter in the Central Valley now rely heavily on agricultural habitats to meet their biological needs. Of the many crops grown here, rice is the most important to wintering waterfowl. In fact, rice fields that are flooded after harvest currently provide more than half of all the food energy available to wintering ducks and geese in this region.
Most of the wetlands managed for waterfowl in the Central Valley are in public ownership or protected with conservation easements. But the number of people living in the Central Valley is expected to more than double during the next 30 years, which will place even greater demands on the region's open space and limited water supplies. Nearly all the region's agricultural land is unprotected and, in many areas, vulnerable to urban sprawl. As a result, DU and its partners hope to add more than 100,000 acres to the region's managed wetland base over the next 25 years. Maintaining sufficient funding for WRP and other Farm Bill conservation programs will be essential to achieving this objective. DU will also continue to work with the agricultural community, private duck clubs, government agencies and other partners to protect wetlands and secure water supplies for key waterfowl habitats in this vital, yet threatened waterfowl wintering area.
—Dr. Mark Petrie and Dr. Fritz Reid