Key Investigator: Laurence L. Strong
The Pacific flyway, a migration path for several species of birds, stretches from Alaska and western Canada south to Mexico (Figure 1) . The Central Valley of California is critical to the survival of international migratory birds, providing winter habitat for 60 percent of the Pacific flyway's waterfowl. The most vital component of this habitat are wetlands (Figure 2) . These areas have steadily diminished over the past fifty years, from five million acres in 1939 to barely 319,000 acres as of 1989. Much of this loss is attributed to increasing agricultural acreage and the pressure of rapid urban growth. In cooperation with the U.S. Fish and Wildlife Service (FWS), researchers at NASA-Ames used remote sensing data to inventory, map and assess seasonal and annual changes in the quality and quantity of migratory waterfowl winter habitats.
The project began by acquiring satellite remotely sensed images and aerial photography of the project's study areas in the Klamath Basin, the Sacramento Valley, San Joaquin Valley Grasslands, and the Tulare Basin. Figure 3 shows a Thematic Mapper image taken of the Sacramento Valley. Here, areas with water which are important waterfowl habitats are indicated by dark and light blue. Data collected in the field included aerial and ground surveys of habitat, as well as annual observations of habitat use and survival of over 120 radio-telemetered pintail duck and white-fronted geese. The remote sensing and field data were organized in a Geographic Information System (GIS). Digital image processing and GIS technology were used to make dynamic maps of water availability, wet-land habitats, and upland habitats including agricultural management practices such as harvesting time, burning and plowing.
The goal of this study was to help the FWS to further develop its use of satellite remote sensing data and technology. Using these tools, resource managers can obtain accurate and timely information which can be used to manage habitats to the benefit of migratory birds.
RESEARCH SITE: Central Valley of California
COLLABORATORS: U.S. Fish and Wildlife Service
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