FAIRBANKS (AP) -- Scientists have found a virus that killed what they suspect is a large number of long-tailed ducks on the North Slope last summer.
Some of the dead ducks were found west of Flaxman Island by Paul Flint, a biologist with the U.S. Geological Survey's Alaska Biological Science Center. Flaxman Island is just off the northwest tip of the Arctic National Wildlife Refuge. Long-tailed duck populations have been declining since the 1970s.
''We may have stumbled into a factor that may, and I underscore may, be important to trends in populations of these particular sea ducks,'' said Dirk Derksen, supervisory biologist for the center in Anchorage.
Breeding populations of long-tailed ducks on the North Slope dropped from 127,000 in 1977 to 113,000 in 1997, according to Bruce Conant with the U.S. Fish and Wildlife Service in Anchorage. Steeper declines were seen in Canada's Northwest Territories, where the 1955 population of 443,000 dropped to 112,000 by 1997. On Alaska's Yukon-Kuskokwim Delta, populations dropped from 233,000 in 1977 to 43,000 in 1997 before rebounding to 105,000 last year.
Biologists don't know exactly how many of the ducks died of viral infections last summer, of course. Flint said he found more than a dozen ducks floating in the lagoons during summer field work.
Thousands of the male long-tailed ducks go to the low barrier islands off the North Slope to molt each year after mating.
''When they finish the molt, they're basically at zero body fat,'' Flint said. ''That's when you might expect birds to be most vulnerable to a virus.''
Flint said female long-tailed ducks, which are busy nesting on more substantial ground along the North Slope, could be hit hard by the virus as well.
After raising their young, the ducks head south. Derksen said recent satellite tracking data from Yukon-Kuskokwim Delta birds shows most spend winters in the southern Bering Sea, Bristol Bay and the Aleutian Islands. Some ducks also winter south along the coast to the Pacific Northwest states, he said.
The virus doesn't seem to be hitting North Slope ducks equally.
Biologists found that half the ducks from Flaxman Island had the live virus. But they found the virus in only 6 percent of ducks captured by another USGS crew near Bodfish Island, 60 miles to the west. No dead ducks were found near that island.
The research was done as part of the work assessing biological impacts of British Petroleum's Northstar offshore oil development west of Prudhoe Bay, Derksen said.
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