been able to document the birdsí spring migration from wintering grounds to
"In migratory bird studies, cross-seasonal research linking wintering and
breeding areas is something of a holy grail," said Dr. John Takekawa, a
wildlife biologist and principal investigator with the USGS Western
Ecological Research Center in Vallejo, California. "Many of these migratory
species nest thousands of miles from where they spend the winter, and it is
difficult to determine which group is from where."
Making such linkages may be vital to understanding alarming declines in sea
ducks of the past few decades. Many sea ducks breed in northern boreal
forest and tundra areas and winter in marine environments. Degradation of
their remote northern breeding habitats, possibly linked to global climate
change, has been suggested by some as a possible explanation for the
decline in these species. At the same time, these ducks may be threatened
by human activities in their major coastal wintering areas. The San
Francisco Bay area supports the largest wintering population of surf
scoters in the Pacific Flyway; however, it is also home to 8 million people
who outnumber the surf scoters by 250 to 1.
Habitats in San Francisco Bay are impaired by pollutants including mercury.
Historically, mercury deposits were mined in the coast range and used for
extracting gold by placer miners in the Sierra Nevada during the gold rush
era beginning in 1849. Mercury accumulated in sediments that were eroded in
the mining process and have since flowed downstream to be deposited in the
Bay. Surf scoters found in San Francisco Bay have elevated mercury levels,
but little is known about the effects of this contaminant on their breeding
"Although surf scoters breed from Quebec to Alaska, our preliminary studies
in 2003 showed that most birds marked with satellite transmitters in San
Francisco Bay were distributed in a band a few hundred miles wide at the
edge of the treeline from the Great Slave Lake to the Great Bear Lake in
the Northwest Territories," said USGS biologist Susan De La Cruz.
Last winter, partnered with the U.S. Fish and Wildlife Service supported by
the Calfed Ecosystem Restoration Program, De La Cruz led the capture and
radio-marking of 90 surf scoters to follow them to their nests. In mid-June
of 2005, the project came to fruition as Matt Wilson, a USGS biologist and
graduate student at the University of California at Davis, Rod King, a
USFWS pilot-biologist, and USGS intern Kenny Farke tracked a
satellite-marked bird to a lake 80 miles east of Yellowknife. After landing
in a float plane, they searched along the lakeshore until finally spotting
the satellite-marked hen sitting on 6 eggs in a downy nest.
"The eggs were freshly laid within a day or two," reported Wilson, who used
a tube to "candle" or age the incubating eggs. Samples from this nest and
others like it will be tested to see if contaminants from populated
southern wintering regions may be having effects on reproduction of
migratory birds breeding in the north.
While this is the first step in documenting breeding effects, the team is
working with biologists from the Washington Department of Wildlife,
Canadian Wildlife Service, Simon Fraser University, and the USGS Alaska
Science Center with support from the North American Sea Duck Joint Venture
to examine the breeding distribution of surf scoters from their major
Pacific coast wintering areas extending from Mexico to British Columbia.
With such cross-seasonal information, it may be possible to better
determine wintering populations that are vulnerable to emerging threats in
the breeding areas such as a proposed natural gas pipeline along the
Mackenzie River and development of extensive beds of oil sands in northern
For more about this USGS surf scoter study, go to: