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Entire Tern Colony Settles on One Island: East Sand

by Barry Espenson
Columbia Basin Bulletin - May 10, 2002

The Caspian terns that assemble each spring, in recent history, in the Columbia River estuary to breed, and hatch and rear their young, seem unruffled by the legal and political gyrations that preceded their return to the Pacific Northwest.

The colony -- believed the world's largest -- has settled in its entirety at the East Sand Island site near the river's mouth. The birds' preferred nesting option is also where humans prefer the birds settle.

The efforts of tribal, state and federal officials and others have for the past few years has focused on shifting the birds -- as many as 9,000 breeding pairs -- from Rice Island to East Sand. It was believed, and that belief has been largely borne out, that the birds would include fewer juvenile salmon in their diets at East Sand. The island's closer proximity to the ocean means more marine fish species such as smelt, anchovies, herring and sardines are available to divert the predatory birds attention from salmon.

The offspring of 12 different stocks of salmon and steelhead are listed under the Endangered Species Act. All pass through the Columbia River estuary on their way to the Pacific Ocean.

Salmon advocates felt the relocation effort was appropriate, but bird advocates said they felt the terns were being improperly scapegoated for declining salmon populations. A trio of bird conservation groups sought and last year received an injunction from U.S. Judge Barbara Rothstein that prohibited any harassment of the birds in the estuary or manipulation of habitat and threatened implementation of the management plan this year.

Federal agencies scurried this spring to settle the lawsuit so the birds could again be steered from Rice Island down river to East Sand. The lawsuit was filed against the U.S. Army Corps of Engineers and the U.S. Fish and Wildlife Service.

The settlement talks culminated on April 2 as the birds began to flock to the area. The Corps, which created Rice Island through the deposition of dredge spoils from the river's shipping channel, immediately went to work. East Sand Island was scraped with a bulldozer and other equipment to create the bare sand nesting habitat terns prefer. Vegetation at the former Rice Island nesting ground was encouraged to overgrow.

The agencies and research involved also deployed decoys and recorded tern sounds to lure the birds to the island -- actions that had been successful in attracting terns to East Sand during the past two nesting seasons. The process took four days.

"They were drawn to the site and tolerant of the early disturbances," consultant Ken Collis said of the birds reaction to the work party.

"We would have preferred to do it earlier but we got it done in time," said Bob Willis, chief of the Corps' Portland District Environmental Resources Branch. "They all seem to be happy with East Sand."

The Corps was being tugged in two directions. A 1999 biological opinion issued by a fellow federal agency -- the National Marine Fisheries Service -- compelled the Corps to eliminate nesting at Rice Island in an attempt to reduce the predation on ESA-listed salmon and steelhead. Rothstein ordered the Corps and USFWS to rethink the tern relocation plan. The USFWS has responsibilities protect the terns under the federal Migratory Bird Treaty Act.

Salmon consumption peaked at an estimated 11.7 million in 1999 when 92 percent of the colony or 8,100 of the nesting pairs were at Rice Island. A pilot study that year shifted 700 pairs to East Sand. The Rice Island terns' diet was 77 percent salmonid while the East Sand birds' percentage was 46 percent.

In 2000 the plan developed by the agencies and researchers was fully implemented and 94 percent of the terns settled on East Sand -- about 9,100 nesting pairs. Researchers estimate the number of nesting pairs by taking aerial photos of the site at the peak of the nesting season in late May. The East Sand terns' diet in 2000 was 47 percent salmonid compared to 90 percent of the 580 pairs that made their home on Rice Island. Overall consumption dropped to an estimated 7.3 million salmonids.

With all 9,100 nesting pairs on Rice Island last year, the total consumption of salmonids fell to an estimated 5.9 million, roughly half that of 1999. The terns' diet last year was 33 percent salmonid.

And so far so good, this year.

The high and low on-colony counts on East Sand Island for the week that ended May 5 were 12,516 terns (May 4) and 8,977 terns (April 29), respectively. Although the colony disturbance rate increased from last week to this week, in general terns have become more settled on the colony and are distributing themselves more evenly across the entire colony area, according to the weekly report issued by researchers.

During the past week, no terns have been observed roosting or attempting to nest in upland areas on Rice Island, Miller Sands Spit, Pillar Rock Sands, or Puget Island, according to the report. On May 1, the continuous monitoring and hazing of terns that had been "prospecting" at the Pillar Rock Sands site was discontinued by the Corps of Engineers. The terns that had been apparently eyeing the site apparently found other accommodations.

Researchers found that 42 percent of the identifiable fish delivered to the East Sand Island tern colony (363) were salmonids. Similar to last week, the majority of the non-salmonid prey items being delivered to the East Sand Island colony were smelt, anchovies, and clupeids (i.e., herring, sardines). Since the birds began arriving in early April, 37 percent of the identifiable fish delivered to the East Sand Island tern colony (1,305) were salmonids, according to the most recent report.

"It seems like they're eating fewer salmon," said Collis, co-principal investigator for the ongoing research related to the relocation effort. In past years at East Sand, the terns a larger percentage of salmon and steelhead in their diets -- as much as 60 to 80 percent -- early in the season before shifting to a diet heavy on marine species.

"It's probably related to the relative availability," of marine species, Collis said. He emphasized that it is much to early in the season to predict diet trends.

The National Audubon Society, Defenders of Wildlife, Seattle Audubon Society and American Bird Conservancy filed the lawsuit early in 2000 challenging the scientific basis for the plan and claiming the agencies' failed to complete an adequate environmental impact study. The groups said the tern management developed by the federal, state and tribal entities did not take into account the long-term welfare of the birds.

The court had issued a temporary restraining order and preliminary injunction in April 2000 prohibiting tern harassment on Rice Island. In December of that the year the court denied the defendants' motion to dismiss the claims.

The August 2001 injunction was appealed by the Corps and USFWS to the Ninth Circuit Court of Appeals, which steered the two sides toward settlement negotiations.

Rothstein ruled that the Corps and USFWS acted illegally when they initiated a plan to turn the terns away from their preferred nesting site without the benefit of a full environmental impact statement.

The settlement required the federal government to prepare and maintain six acres of suitable tern habitat on East Sand Island, near the mouth of the Columbia River. The bird groups are pleased with the work that has been done and that the terns have a home. But East Sand is seen as a partial solution. The bird groups, like those involved in the relocation plan, worried about long term solutions such as finding additional nesting grounds for the birds.

"The potential for disaster is pretty great," said Alex Morgan, conservation director for the Seattle Audubon Society. With what is estimated to be two-thirds of the Pacific Coast and one-quarter of the North American tern population concentrated in one spot, disease or natural disasters such as flooding during the nesting could cause great harm, Morgan said.

Efforts to find additional habitat along the coast or inland have been rebuffed by local officials that fear relocation only moves the problem.

"This is not so much a difficult wildlife management issue as it is a difficult people management issue," Willis said. With listed fish stocks in nearly every Columbia Basin watershed, local officials worry terns will retard salmon recovery efforts.

Longer term requirements of the settlement agreement are that the federal agencies complete three studies related to Caspian terns -- a predation analysis, tern status assessment and nest site feasibility -- on the way to producing a full EIS.

Once these studies are completed, the USFWS will take the lead in preparing a long-term management plan and an environmental impact statement for Caspian terns in the Columbia River estuary. The draft is due out no later than Oct. 1, 2004, according to the agreement.

Link information:
Columbia Bird Research:
Draft reports:

Barry Espenson
Entire Tern Colony Settles on One Island: East Sand
Columbia Basin Bulletin, May 10, 2002

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