The Project: What We Are Doing And Why

As many as 80,000 surf scoter have been counted in San Francisco Bay, making the region home to the largest southernmost wintering concentration on the Pacific coast. Sea ducks are under investigation because of evidence indicating widespread population declines in this group. Recent midwinter surveys in San Francisco Bay have shown that numbers of waterfowl are declining, including surf scoters. Pollution may be a source of the problem, and the San Francisco Bay Estuary Field Station of the U. S. Geological Survey, Western Ecological Research Center has been leading studies on the ecology of wintering populations and their contaminant risks, including cross-seasonal studies linking to their migration and breeding. Scoter studies are being conducted by many organizations in western North America, including the Canadian Wildlife Service, Washington Department of Fish and Wildlife, Ducks Unlimited, Simon Fraser University, and University of Wyoming, coordinated through the Sea Duck Joint Venture of the North American Waterfowl Management Plan.

As a part of our ongoing studies on San Francisco Bay (SFB) surf scoter, we are trying to determine their migration routes and breeding grounds, as well as document cross-seasonal effects of contaminants on their reproduction. During March 2003 we captured SFB scoter using a net gun and marked them with both satellite transmitters (14 females) and radio transmitters (28 total, males and females). We are now tracking the migration routes of these birds to determine major stopover sites and migration timing. This study is being conducted in coordination with other ongoing scoter research projects in Puget Sound, the Strait of Georgia, and Prince William Sound. During June and July 2003, the locations of satellite-marked scoters will be used to define breeding ground search areas in Alaska and Canada. Once birds with satellite transmitters settle in nesting areas, we will fly aerial surveys to determine if birds marked with radio transmitters are also nesting in the vicinity. Then, we will use a combination of aircraft and boats to access nest sites and collect one egg and feathers found in the nest. Eggs will be analyzed for contaminants such as mercury and selenium, to try to determine if these pollutants occur in scoter eggs at levels that cause problems with development and hatching success. Methods such as stable isotope analysis will be used to distinguish birds that molt and winter in different areas.

Objectives:

1. Reveal linkage between wintering, migration and breeding areas for surf scoters in the Pacific Flyway.
2. Determine cross-seasonal persistence of contaminants and breeding risks.

• The study plan