The winter gathering spot of spectacled eiders in the sea ice south of St. Lawrence Island.
Matt Sexson, USGS Alaska Science Center
Sexson duplicated Margaret Petersen’s study, capturing birds in northern and southwestern Alaska. From 2008 to 2012, he received more than 7,000 transmitted locations from the birds. Part of his degree work is to compare his results to those found in the 1990s.
The birds’ more recent signals confirmed that they clump in the same areas south of St. Lawrence Island from mid-October until mid-April.
“Most likely, there’s 350-to-370 thousand birds there right now waiting for breakup,” Sexson said. Once snow melts from tundra to expose nesting sites, birds will return to either northern or southwest Alaska, or more likely Siberia.
“Only about five percent of the world’s population breeds in Alaska,” Sexson said. There is not much information on the birds’ lives in northern Russia, so biologists don’t know if Alaska birds dropped in numbers or moved to Siberia during breeding season.
But Sexson and others know the birds spend half of their year in the emptiness of the Bering Sea between St. Lawrence and St. Matthew islands. The northern Bering Sea has plenty of clams and snails, but that prey is available is places that are less bleak. Why spend six months there?
Sexson has a few ideas. One is that male birds court females while they are floating en masse. There, they maximize their chances of finding a mate (they find a new one each year).
Gathering in such a harsh place might be due to “some form of genetic relic,” Sexson said. The birds might be remembering a forgotten landscape from 20,000 years ago, a hypothesis he will check using the birds’ genetic material.
During the last ice age, their current wintering area might have been a shoreline of the Bering Land Bridge. Changing landforms and environmental conditions have doomed other animals, but spectacled eiders may have found a location that has somehow worked for them as their neighbors changed from mammoths to walruses.
Since the late 1970s, the director of the Geophysical Institute at the University of Alaska Fairbanks has supported the writing and free distribution of this column to news media outlets. This is Ned Rozell’s 20th year as a science writer for the Geophysical Institute.