LONGVIEW — A carrot-and-stick project to cut the number of salmon-gobbling terns on an island near the mouth of the Columbia River is set to begin, scientists from the Army Corps of Engineers say.
Work will begin with the building of an island designed to attract migrating Caspian terns at Fern Ridge Lake near Eugene, Ore., where a small transient group of terns has been spotted, corps wildlife biologist Geoffrey Dorsey said Thursday.
The purpose is to reduce the loss of salmon and steelhead, especially from 13 endangered or threatened runs, to terns that flock to East Sand Island between Chinook and Astoria, Ore., as the young fish head out to sea.
Over the past decade, the island has become home to what is believed to be the world’s largest colony of Caspian terns, about 9,000 birds that eat about 5 million juvenile salmon annually.
The corps’ project includes elimination of about three-fourths of the tern habitat on the island while creating twice as much nesting potential at a wildlife refuge near Port Angeles, at Fern Ridge and two other inland Oregon lakes, and at three sites in the San Francisco Bay area.
To draw attention to the new breeding sites, scientists plan to deploy decoy terns, sound the bird’s call through a sound system and assure plenty of food in the form of bass, carp and goldfish.
Returning north in the spring, terns readily choose new nesting spots, and appealing areas away from the mouth of the Columbia could keep the birds away from the Columbia salmon runs for good, scientists say.
“If the food is there and the habitat is there and there’s a good opportunity for successful nesting … they will try to nest there,” said Daniel Roby, an Oregon State University wildlife ecology professor serving as lead researcher for the project. “We know it works pretty well for Caspian terns.”
The relocation strategy, developed as part of a settlement of a lawsuit brought by the National Audubon Society and other groups, also could benefit the terns.
Breaking up the East Sand Island group will ease the impact of disease, storms, human disturbances and other threats that could be catastrophic to a concentrated colony, wildlife officials said in 2005, when the final project was announced. Cost of the project has been pegged at $2.4 million for habitat work and more than $100,000 a year for operations.
Historically, Caspian terns bred in sandy or gravelly areas on lakes east of the Cascade Range, Dorsey said.
When those habitats began to diminish in the 1920s, the birds moved west to areas such as Grays Harbor and San Francisco Bay.
In the 1990s, scientists found terns nesting on Rice Island, a heap of sand dredged from the Columbia River shipping channel, were eating young salmon by the millions.
Five years ago, officials bulldozed open sand on East Sand Island to push the terns about 15 miles closer to the ocean, where they fed more on less valuable and more abundant marine fish.
The flock has flourished so much that East Sand now harbors 70 percent of North America’s tern nests.
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