March 2000
Contact: Rocky Beach, WDFW Wildlife Program, (360) 902-2510

Since 1986, a growing colony of Caspian terns has been nesting on Rice Island 20 miles from the mouth of the Columbia River, consuming millions of salmon smolts as they migrate to the Pacific Ocean. This has prompted increasing concern by federal and state agencies, the tribes and others, since many of those young salmon are members of species listed as "threatened" or "endangered" under the Endangered Species Act (ESA).

To address the issue of tern predation on listed salmon, the U.S. Army Corps of Engineers plans to scare – or "haze" – the birds off the island when they return to nest this year. Scientists from Oregon State University (OSU) also plan to use decoys and recorded calls to attract some of the terns to East Sand Island, approximately 15 miles down river near the mouth of the Columbia. A pilot project conducted in 1999 found that the terns consumed a much lower proportion of salmon at East Sand Island than at Rice Island.

This year's effort to move the terns down river from Rice Island to East Sand Island is scheduled to begin April 1, 2000. The Washington Department of Fish and Wildlife (WDFW) supports the Corps' efforts to reduce tern predation on Columbia River salmon smolts and helped to develop this year's management plan as a member of a working group composed of neighboring states, tribes and federal agencies. WDFW will not, however, participate directly in the effort to displace the terns from Rice Island, which is in Oregon.

Caspian tern populations

Caspian terns are gull-like migratory birds that winter in southern California and Mexico before flying north to nest in the Pacific Northwest. The Caspian tern colony on Rice Island, a 230-acre deposit of dredged material east of Astoria, Oregon, is the largest of its kind in North America. Since 1986, the colony has increased by over 600 percent to a total of 8,100 breeding pairs in 1999. Prior to 1984, colonies were scattered from Grays Harbor and Willapa Bay to northern Puget Sound.

Impact on salmon

The terns on Rice Island nest and rear their young from April through July, which is also the peak migration period for juvenile salmon. Research has shown that the birds rely on salmon for 77 percent of their diet during that period, consuming approximately 12 million of the 100 million out-migrating smolts that reached the Columbia River estuary in 1997. At that rate, the Corps estimates that in 1999 the terns consumed 647,000 smolts listed under the ESA. The impact of this level of smolt predation on the returning population of endangered stocks is unknown, particularly as compared to more significant salmon mortality factors such as dams, harvest and habitat loss.

The plan for 2000

The Corps' long-term goal for the Rice Island terns is to disperse the birds into smaller colonies spread over a wide geographic area used by terns in the past to reduce predation on ESA-listed species. This approach also benefits the terns in that it will reduce the possibility that the species could be jeopardized by a catastrophic event such as an oil spill.

For 2000, the immediate goal is to move the colony to East Sand Island, closer to the mouth of the Columbia. The advantage of moving the colony to East Sand Island is that the terns nesting there appear to have a more varied diet than those at Rice Island. Research conducted during the 1999 pilot project found that salmon made up only 44 percent of the diet of terns relocated to East Sand Island, compared to 77 percent for those remaining at Rice Island. Other sites have been considered but require additional assessment.

Terns prefer to nest in sandy areas, clear of debris. To help attract terns to East Sand Island, the Corps will maintain four acres for nesting on the island, which were initially cleared of vegetation and debris in 1999. A team from OSU will then use decoys and recorded calls to attract terns to the island, while other workers contracted by the Corps will chase birds off Rice Island – as well as neighboring Miller Sands Spit and Pillar Rock Island – throughout the nesting season.

The Corps has filed an Environmental Assessment stating that its 2000 tern management plan will be consistent with the Migratory Bird Treaty Act, noting that the agency does not plan to use lethal measures to displace the birds and that the number of terns in the region is rapidly increasing. While WDFW supports the Corps' plan, the agency also recognizes its responsibility to protect Caspian terns and will be monitoring the situation closely in the Columbia River and in areas such as Willapa Bay, Grays Harbor and Puget Sound. WDFW will continue to insist that studies be conducted on the distribution, number and diet of birds in all areas and that contingencies be developed to ensure that the tern relocation efforts do not result in significant predation on salmonids outside the Columbia.

Return to WDFW Home Page