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New island might have terns turning to Fern Ridge.

Byline: Mike Stahlberg The Register-Guard

The water level at Fern Ridge Lake is dropping steadily, a normal function of the "winterizing" routine that readies flood-control reservoirs in the southern Willamette Basin to contain runoff of rain and snowmelt.

When the reservoir refills next spring, the water will surround a new man-made island of about one-acre in size, if the U.S. Army Corps of Engineers gets its way.

The island isn't intended for sunbathing, picnics, or other human recreation.

Rather, its pea gravel surface will serve as a love nest for Caspian terns, a fish-eating bird that frequents Fern Ridge in small numbers during migrations. However, terns do not nest there, due to the lack of suitable sand or gravel areas protected from predators.

The Corps of Engineers hopes that up to 300 breeding pair of terns will set up housekeeping on the as-yet unnamed Fern Ridge Island.

It's part of a grand plan to reduce the population of terns on East Sand Island near the mouth of the Columbia River.

The Corps wants to do that because the 9,000 pairs of terns that breed and nest on six-acres of East Sand Island are a significant source of predation on juvenile salmon and steelhead.

According to a draft Environmental Assessment filed earlier this month, the Columbia River terns consumed an estimated 5.3 million salmon and steelhead smolts in 2006. Thirteen stocks of salmonids protected by the federal Endangered Species Act are included in their prey.

At the same time new nesting habitat is being created at Fern Ridge and seven other sites on the West Coast, the Corps would gradually reduce suitable habitat at East Sand Island by two-thirds or more.

Terns are apparently adept at locating suitable nesting areas, which are becoming scarce due to development and other factors.

After all, the world's largest colony of Caspian terns resides on East Sand Island, which didn't even exist until the Corps of Engineers dumped dredging spoils from river channel clearing in shallow areas of the Columbia River Estuary. The increased predation on salmon was an unforeseen result of that work.

While there is adequate food supply for any terns that settle at Fern Ridge, luring terns there is not expected to adversely impact the lake's fish populations, scientists say.

Fern Ridge Lake holds populations of bluegill, black and white crappie, brown bullhead, common carp, goldfish and largemouth bass.

"The establishment of a tern nesting colony at Fern Ridge Lake is not anticipated to noticeably lower the population of any fish species at the lake," the environmental assessment says.

The document says relocating terns would be beneficial to that species because about 70 percent of the total population nests on East Sand Island, making them vulnerable to catastrophic events such as storms or a disease outbreak.

"The nesting habitat we create or enhance along the terns' natural migratory paths will provide for a more natural, dispersed population than the concentrated population on EastSand Island," Col. Thomas O'Donovan, the Corps' Portland District Engineer, told the Columbia Basin Bulletin.

"The expanded range of nesting grounds also will provide a diet of fewer Columbia River salmon and support our continued efforts to restore ESA-listed fish in the basin."

Funds for the work will come from the Corps' Columbia River Fish Mitigation Program. The Corps hopes to begin work on the Fern Ridge island before the end of the year.

The draft environmental report is up for public review and comment through Nov. 5. The document and related public notices are available online at

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Mike Stahlberg can be reached at
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Title Annotation:Outdoors Columnist
Publication:The Register-Guard (Eugene, OR)
Date:Oct 23, 2007
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