USGS Western Ecological Research Center

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Migration of Surf Scoters Along the Pacific Coast - Spring Migration 2006

Surf scoter
A large proportion of diving ducks in the Pacific Flyway are found in the San Francisco Bay estuary during the winter. Up to 80,000 surf scoters (Melanitta perspicillata), the largest southernmost concentration on the Pacific coast, have been counted in the estuary. Sea ducks are under investigation because of evidence indicating widespread declines in this group. Pollution may be a source of some of the problems. In this study, we are capturing and marking scoters with radio transmitters in San Francisco Bay to determine their late winter, spring migration, and breeding distribution. The San Francisco Bay Estuary Field Station of the U. S. Geological Survey, Western Ecological Research Center located in Vallejo, California has been leading studies on the ecology of wintering waterbird populations and their contaminant risks, including cross-seasonal studies linking them to migration and breeding areas.

Project Details

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 January 2006 we captured SFB scoters 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 2006, 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.


  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.

USGS Contact For This Project
Susan De La Cruz
(415) 859-1511
San Francisco Bay Estuary Field Station
505 Azuar Drive
Vallejo, CA 94592
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