A state effort to lure local Caspian terns - displaced by development from their nesting site at the old Asarco mill - to a barge in Commencement Bay was cut short by tribal concerns about all the salmon the birds were eating, some 78 percent of the birds' diet, said Jeff Koenings, director of the state Department of Fish and Wildlife. "We can understand the tribe's concerns, given that they have a major hatchery facility on the nearby Puyallup River" and that the area's wild salmon stocks are listed under the Endangered Species Act. The state offered the barge as temporary housing to prevent mass migration of the local flock to the lower Columbia River, where terns, protected by the Migratory Bird Treaty Act, have taken a heavy toll on migrating salmon and steelhead smolt - some from threatened stocks. The barge birds were shooed away May 31 and the barge removed. With the destruction of the barge nests, there are no tern nesting colonies in the Puget Sound area. About 500 pairs had been nesting at Asarco for the past three years. The birds arrive in April or May and stay through September, wintering along coastal California and Mexico.