USGS Western Ecological Research Center

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Suisun Marsh is a critical habitat for wintering and breeding waterbirds in California. USGS is working with the California DWR to examine the trends in bird decline and to assess the habitat factors driving long-term survival of waterfowl, rails, and other birds in this important area.

Pintail drake and hen


The importance of the Suisun Marsh, California, as a waterfowl-use area is widely known and has a long history. But as of 2014, waterfowl abundance is below the Central Valley Joint Venture’s population objective for 300,000 ducks wintering in Suisun Basin, and well below the nearly 370,000 waterfowl that typically wintered there during the 1950s. 

Long-term population trends for dabbling ducks and geese are declining in Suisun Marsh, even after accounting for California-wide population trends, indicating that proportionately fewer dabbling ducks and geese are choosing to winter in Suisun Marsh than historically. Suisun Marsh also supports among the highest densities of breeding ducks in North America, and plays an important role in duck production within California. 

With more than 90 percent of California’s wetlands lost, Suisun Marsh represents one of the last remaining contiguous wetland habitats in the state. In order to understand and manage waterbird populations and habitats in Suisun Marsh, the California Department of Water Resources has partnered with the USGS Western Ecological Research Center and other project partners to these address information needs.

This project seeks to:
  1. Conduct waterfowl abundance surveys to estimate an index of population size for wintering waterfowl in Suisun Marsh.
  2. Examine waterfowl habitat use and movements using telemetry.
  3. Examine waterfowl body condition and assess temporal changes.
  4. Examine the nesting ecology of waterfowl and long-term trends in nest survival and nest density.
  5. Examine duckling survival, brood ecology, habitat use, and movements in relation to wetland habitats and salinity.
  6. Assess long-term trends in waterfowl demographic rates and population viability.
  7. Assess the value of food types and different wetland habitats to waterfowl in Suisun Marsh, and estimate carrying capacity of Suisun Marsh for waterfowl.
  8. Develop and conduct continuous rail (California Ridgway's Rail and Black Rail) surveys using acoustic recording devices within Suisun Marsh.
  9. Examine rail habitat availability and develop metrics of habitat quality from habitat use and movements using telemetry where appropriate.

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