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Draft EIS Calls for
Moving Most Estuary Terns Elsewhere

by Barry Espenson
Columbia Basin Bulletin - July 23, 2004

The "preferred alternative" in a management analysis released today (July 23) would seek to shift 60 to 70 percent of the Caspian terns that now nest in late spring and summer in the lower Columbia River estuary to sites elsewhere in Oregon, in Washington and in California's San Francisco Bay.

The goal is to reduce the amount of avian predation on the juvenile salmon and, particularly, steelhead swimming toward the ocean. It is also intended to reduce the chance that some catastrophic event might occur at East Sand that would devastate the collection of terns that represents 70 percent of all the terns in the Pacific region.

The shift would be made over a 3- to 5-year period by gradually allowing vegetation to overgrow most of the terns' favored nesting site on East Sand Island and creating or enhancing habitat elsewhere.

"We believe that limiting nesting habitat in the Columbia estuary and attracting terns to other sites would benefit terns and salmon," said Dave Allen, the U.S. Fish and Wildlife Service's Pacific Region director. "By reducing the size of the estuary colony fewer young salmon would be eaten and there would be less of a chance that a large portion of the regional tern population, concentrated in this single location, could be harmed by storms, predators, human disturbance and disease."

The draft Environnental Impact Statement on Columbia estuary tern management will be open for public comment through Sept. 20.

The draft document, prepared in cooperation with the U.S. Army Corps of Engineers and the National Marine Fisheries Service (NOAA Fisheries), is part of a 2002 settlement agreement between the USFWS and the Corps and the National Audubon Society, Defenders of Wildlife, Seattle Audubon Society and the American Bird Conservancy. In the settlement agreement, the agencies agreed to maintain six acres of habitat on East Sand Island near the mouth of the Columbia River until 2005, complete three studies, and prepare a tern management plan and EIS for implementation in 2005.

The preferred alternative outlined in the draft identifies identified potential management locations for terns at Summer, Crump and Fern Ridge lakes in Oregon, Dungeness National Wildlife Refuge in Washington, and three sites in California's San Francisco Bay. All of the sites are on public land and most already are occupied by terns.

The East Sand Island colony near the mouth of the Columbia River is considered the world's largest, with about 9,000 pairs. The Island is the result of dredge spoils that created perfect nesting conditions amidst an abundant supply of federally protected juvenile salmon and steelhead. Caspian terns typically nest in relatively small numbers (e.g., 100-1,500 pairs) on islands along the coast and on interior lakes.

The number of terns nesting in the Columbia River estuary has grown significantly since it was first documented in 1984. Caspian terns have concentrated in the estuary because historic nesting sites have been lost elsewhere in the Pacific Coast/Western region and human-created dredge-spoil islands in the estuary offered stable nesting habitat close to abundant supplies of fish.

In 1999 and 2000, the Corps of Engineers relocated terns to East Sand Island from Rice Island 15 miles up the Columbia River. As the terns' diet shifted to mostly marine fish, such as anchovies, tern predation on juvenile salmon and steelhead dropped by 66 percent.

The bird protection groups filed the lawsuit protesting the move over concerns about the birds' welfare. The court eventually ruled that the Corps and USFWS acted illegally when they initiated a plan to turn the world's largest colony of Caspian terns away from their preferred nesting site without the benefit of a full environmental impact statement.

Researchers estimated that last year terns from the East Sand colony ate 4.2 million juvenile salmonids during 2003, according to a draft 2003 summary report on the summer field season. That compares to a peak of an estimated 12.4 million consumed by the terns in 1998, the second-year of an ongoing study that has been financed by the Bonneville Power Administration.

However, the number of Caspian terns on East Sand Island is expected to increase, as will the number of protected young salmon and steelhead consumed by the birds. Thus, NOAA Fisheries remains concerned that terns may be negatively impacting Columbia River salmon recovery, according to a USFWS press release.

The preferred alternative proposes to disperse from 5,000 to 6,500 pairs from East Sand Island by reducing the amount of nesting habitat there from 6 acres to about 1-1.5 acres. The potential management location for terns at Dungeness National Wildlife Refuge -- at the east end of the Strait of Juan de Fuca near Port Townsend -- is expected to absorb the largest share -- from 100 to 3,500 mating pairs. A small colony of less than 300 terns nest there now.

Small colonies at Summer, Crump and Fern Ridge lakes in Oregon are expected to grow by from 5 to 300 pairs. Summer and Crump lakes are inland in south-central Oregon --Summer near Paisley and Crump near Lakeview. Fern Ridge is near Eugene.

Of the three in California's San Francisco Bay, Brooks Island's colony is expected to grow by from the existing 900 pair to 1,500. Two new sites in the bay are expected to draw 100 to 1,500 tern pairs.

If the preferred alternative is selected, terns are expected to be attracted to the new sites in a couple ways: By reducing available habitat on East Sand Island, the terns will have to look for alternate nesting sites. Because they are highly social birds that nest in colonies they would likely head to the other areas where terns already are nesting. At the few sites where terns are not already nesting, decoys and recorded tern sounds would be employed to attract terns, much as it was done when the birds were moved from Rice to East Sand.

Most of the potential sites already have terns nesting. The only exceptions are one of the islands in San Francisco Bay and the three new islands the agency proposes creating in Summer Lake. Terns already do nest at Summer Lake but the preferred alternative calls for creating additional nesting habitat there.

NOAA Fisheries has estimated that a reduction in the tern colony to 3,125 nesting pairs would result in a 1 percent or greater increase in the population growth rate for all Columbia River basin steelhead stocks listed under the ESA. Steelhead were the focus of the analysis because they are the stock most favored by the predatory terns.

"Because of uncertainties in the model, we propose to manage for a more conservative range of nesting pairs on East Sand Island to ensure an increase in the population growth rate for all Columbia River Basin steelhead ESUs," according to the EIS executive summary. About 2,500 to 3,125 pairs of terns would still be able to nest on East Sand Island with the nesting sized reduced form 6 to 1-1.5 acres.

"Thus, estimates of the potential benefits to reducing tern predation are the greatest for steelhead but other Columbia River salmonid ESU's subject to tern predation would also benefit," according to the summary. There are 12 listed salmon and steelhead "evolutionarily significant units" in the Columbia basin.

Biologists estimate that under the preferred alternative, luring the terns to other breeding sites could temporarily affect tern nesting success and possibly the number of terns in the region, but that tern numbers are expected to stabilize over time. While the stabilized number of birds would possibly be lower than the current total population, it is estimated to be well above the approximately 6,200 pairs observed in the late 1970s and early 1980s.

In recent years, terns were documented to have nested on about 60 sites scattered throughout the Pacific Coast region, including Alaska. In Washington, breeding activity was first recorded in the 1950s at small coastal colonies in Grays Harbor. The Grays Harbor area once supported the largest colonies of breeding terns in the region.

Public comment on the Draft EIS is being accepted until September 20, 2004. A record of decision and final EIS is expected to be released in February 2005.

Written comments on the Draft EIS may be sent to Nanette Seto, Migratory Birds and Habitat Programs, U.S. Fish and Wildlife Service, 911 N.E. 11th Avenue, Portland, Oregon 97232, or faxed to 503-231-2019, or sent by e-mail to

Barry Espenson
Subbasin Plans Make Deadline; Now Comes Science Review
Columbia Basin Bulletin, July 23, 2004

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