Plans to redistribute a portion of the world's largest breeding colony of Caspian terns to Crump Lake in the Warner Valley of south central Oregon are moving forward, the U.S. Army Corps of Engineers announced last week.

The Corps issued a draft Environmental Assessment that addresses the environmental impacts associated with the Crump Lake phase of the plan. It provides information to supplement and update previous National Environmental Policy Act documents.

The draft assessment is available for public review and comment through Jan. 25. The document and the public notice are available on the Corps' Web site at https://www.nwp.usace.army.mil/pm/e/en_plan_avian.asp.

The avian predation program aims to reduce the number of young salmon consumed by avian predators in the Columbia River estuary and thus improve the survival of fish listed as threatened or endangered under the Endangered Species Act. There are 13 listed salmon and steelhead stocks that pass through the estuary on their way to the Pacific Ocean.

The Corps and the U.S. Fish and Wildlife Service previously determined that redistributing terns from the estuary's East Sand Island to alternative nesting locations in the western region is the most biologically sound method to alleviate their predation impacts on salmon migrating to the Pacific Ocean.

The East Sand colony has averaged more than 9,000 pairs in recent years, making it the largest in the world. Researchers estimate that the East Sand colony consumed 5.3 million young salmonids in 2006 and an average of 4.2 million from 2001-2005.

A November 2006 Corps record of decision aims to create or enhance a total of about 7 acres of habitat at Summer, Crump, and Fern Ridge lakes in Oregon; and San Francisco Bay (Brooks Island, Hayward Regional Shoreline, and Don Edwards NWR).

The decision documented the Corps' adoption of the U.S. Fish and Wildlife Service's Final Environmental Impact Statement for "Caspian Tern Management to Reduce Predation of Juvenile Salmonids in the Columbia River Estuary." The ROD modified that EIS, dropping a relocation site at Washington's Dungeness Spit because of potential impacts to listed salmon stocks there.

Under the plan, the 6-acre tern nesting site on East Sand Island will gradually be reduced as tern nesting habitat is created or enhanced at the other locations. The plan is to reduce the suitable nesting habitat at East Sand Island to 1.5 to 2 acres.

The redistribution is expected to benefit the terns by reducing the potential risk of exposing a large segment of the regional tern population to catastrophic events such as predators, storms and disease. The East Sand colony comprises about 70 percent of the terns' western region population.

"Crump Lake will provide nesting habitat along the terns' natural migratory paths and provide for a more natural, dispersed population than the concentrated population on East Sand Island," said Geoff Dorsey, Portland District wildlife biologist.

The proposed action entails restoration of an approximately one-acre island for Caspian tern nesting habitat in the south-central Oregon lake. Social attraction measures will be used in an attempt to draw Caspian terns to Crump Lake. An existing island, typically inundated when Crump Lake is full, would be restored and slightly enlarged from the remnant that currently remains. The original island was partially dismantled by artifact hunters circa the 1950s and was later eroded by wave action.

Terns have been known to nest at the lake intermittently over the years. A similar nesting island at Fern Ridge Lake near Eugene, Ore., is anticipated to be constructed just prior to the proposed island at Crump Lake.

Island construction is targeted for February-March 2008 to take advantage of the current dry lakebed and wintertime freezing temperatures, according to the draft document. That would greatly simplify the construction effort over a full lake condition when material and equipment would have to be barged via shallow draft vessel to the island.

A full lake condition would require more cost and effort, including development of a rudimentary on/off loading facility such as a rock fill bulkhead extending from the lake shoreline to water of sufficient depth for barges to access.

Materials from a local quarry would be used for the new island fill, a mixture of cobbles, gravel, sand and some fines. The cobbles and gravel are angular to subrounded in shape, indicating a combination of talus and river deposits. The larger rocks in the quarry, identified as Steens basalt, will be used for the riprap surrounding the new island. Roughly half the basalt is vesicular. Rocks up to 200 pounds will be used for riprap on the east, north, and west sides of the island, while rocks greater than 200 pounds will be placed on the south side facing the prevailing winds.

A pile of black, coarse, crushed sand located at the quarry will be used for the top foot of the island.

The establishment of a tern colony at Crump Lake is not expected to impact fish populations, according to the draft document. The lake supports a large population of native tui chubs and introduced black and white crappies, along with other sunfish species, brown bullheads and the federally-listed native Warner sucker. Red-band trout, a native species, are also present at Crump Lake and tributary streams.

The U.S. Fish and Wildlife Service says that the development of a nesting colony of Caspian terns at Crump Lake is likely to result in incidental take of Warner sucker in the form of direct mortality, harm and harass or impairment of biological patterns.

The draft EIS estimates that up to 21 Warner sucker may be taken as prey due to the increase in nesting habitat, but most will be younger age class fish.

"Due to the natural expected high rate of mortality in young fish, the additional mortality of a maximum of 21 Warner sucker each nesting season will not be significant," the draft says. "Take of 21 sucker could represent 0.4 percent of the total estimated population of Warner sucker including stream habitat."

The redistribution project includes environmental documentation and detailed work plans for the development of Caspian tern nesting sites at the six locations over approximately the next five years.

The Corps anticipates construction of the first site at Fern Ridge Lake in Oregon to begin in January 2008 with completion in February 2008.