Biologists hope to give Columbia River predator birds other nesting options

By John Trumbo, Herald staff writer

A Caspian tern catching five juvenile salmon or steelhead for itself and a chick each day can take 150 fish a month from the Columbia River.

Make that 300 nesting pairs of birds at Crescent Island, each with a couple of chicks, multiply times five months of summer and fall for salmon and steelhead migration, and that equals 500,000 fish going down bird gullets.

And that's why the Corps of Engineers and National Oceanic and Atmospheric Administration are concerned too many terns could upset the balance for salmon.

"I believe the (Columbia River) system is somewhat out of balance. Predatory birds from throughout the West, from the Rockies to the West Coast, are relocating to the Columbia River Basin," said Ritchie Graves, chief of the Columbia River Power System for NOAA Fishery Services.

Graves, whose office is in Portland, said the Columbia River Basin is popular with terns and cormorants because food is abundant.

Dan Roby, associate professor of fisheries and wildlife at Oregon State University, said in a 2003 research paper the increase of fish-eating birds in recent years "might be sufficient to inhibit recovery of some Columbia River Basin salmonid stocks in serious decline."

The answer biologists are looking at is how to entice the birds to go elsewhere.

Graves said the goal is to reduce tern habitat on the Columbia while providing nesting options elsewhere.

They've had some success, such as at East Sand Island near the mouth of the Columbia, which had nearly 10,000 nesting terns. Some apparently have moved away, which Graves and Roby say is the best thing that could happen.

The Corps remade an island at Crump Lake in southcentral Oregon 18 months ago to attract terns away from the Columbia. That project, with Roby's oversight, has become home for more than 500 terns, Graves said.

Building on that success, the Corps had a 22,000-square-foot floating island set up at Dutchy Lake in southeastern Oregon in February. After three months, it's attracted a handful of birds and officials hope more will find it.

Amy Echols, a Corps spokeswoman in Portland, said the unique project involved a patchwork of 328 panels consisting of recycled plastic carpet matting laid over a lattice of plastic bottles. A top layer of pumice provides the sandy base that terns want for nesting, she said.

If it is successful, the Corps plans to build more relocation islands in Oregon and northern California to draw terns away from the Columbia River.

"The strategy is to do this without putting terns on the Endangered Species Act list," Graves said.

But what works for terns won't work for cormorants, which Graves said "are generalists on where they want to live. They're a bigger challenge."

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Sunday, Jul. 05, 2009

Biologists hope to give Columbia River predator birds other nesting options

By John Trumbo, Herald staff writer