The initiative seeks to redistribute a portion of what researchers say is the largest Caspian tern colony in the world. Last year, OSU researchers counted 9,900 pairs of nesting terns on East Sand Island near the mouth of the Columbia River which accounts for an estimated 70 percent of all Caspian terns nesting in the Pacific Coast region from Alaska to Baja California.
In the late 1990s, the Corps relocated the terns to East Sand Island from another Columbia River location 16 miles upstream Rice Island after an OSU-led research team discovered the colony there had eaten some 12 million young salmon in one year, an estimated 10 percent of the juvenile population from throughout the entire Columbia basin. East Sand Island is only five miles from the ocean and the waters there support a wider variety of fish, including herring and anchovies, than do the fresher waters upstream near Rice Island.
"Terns are fish-eating birds that eat large quantities of small fish," Roby said. "When we looked at what the terns on Rice Island consumed, we found that three-fourths of their diet was juvenile salmon and steelhead. That is not good."
Rice Island was, perhaps, the "worst possible location" for the world's largest Caspian tern colony at least, from the perspective of restoring the 13 threatened or endangered stocks of Columbia Basin salmon and steelhead, the OSU researcher said.
This early relocation worked better than anyone expected, Roby pointed out. The East Sand Island colony now consumes less than half as many young salmon and steelhead as the former Rice Island colony an estimated 4-6 million juveniles per year but "that is still too many," he added. Now the project investigators are following up with the planned second phase of the initiative, an effort to redistribute the terns to more nesting sites away from the Columbia River.
"The world's largest Caspian tern colony is still located in the Columbia Ri
|Contact: Dan Roby|
Oregon State University