The U.S. Army Corps of Engineers has issued a draft environmental assessment of its plan to redistribute part of the world's largest breeding colony of Caspian terns from the Columbia River estuary to Malheur Lake, near Burns in southeastern Oregon.
The Corps plans to build a one-acre elliptical rock fill island in the south central portion of the lake about 2,000 feet from the shoreline. This deepest and most consistently watered area can be used by Caspian terns as a nesting location at least nine months of the year.
The island and related social attraction measures are aimed at attracting migrating terns to the area instead of the Columbia River estuary. This is expected to reduce their consumption of juvenile salmon attempting to migrate to the Pacific Ocean that are listed as threatened or endangered under the Endangered Species Act.
Corps biologists also expect the terns to provide a local benefit by helping to manage the carp population in Malheur Lake.
This redistribution is also expected to benefit the terns by reducing the exposure of part of their population to catastrophic events such as predators, storms and disease. The East Sand Island colony in the Columbia River estuary comprises about 70 percent of the terns' western region population.
"Malheur Lake and other sites provide nesting habitat along the terns' natural migratory paths, leading to a more natural, dispersed population than the concentrated population on East Sand Island," said Paul Schmidt, Portland District wildlife biologist.
The overall redistribution project is reducing the tern's nesting habitat on East Sand Island while constructing alternative nesting sites elsewhere in the region. Since 2009, the Corps has reduced the size of the East Sand Island nesting site by two-thirds and constructed islands at Fern Ridge, Summer and Crump lakes in Oregon and Orems Unit and Sheepy and Tule lakes in California, with additional California sites planned.
The islands already constructed have attracted more than 1,000 mating pairs of an estimated East Sand Island population of 9,000 to 10,000 pairs. The Corps estimates the redistribution project when completed will help 2.4 to 3.1 million additional juvenile salmon survive their passage through the Columbia River estuary each year.
The proposed Malheur Lake project is a collaborative effort between the Corps' Portland District, the U.S. Fish and Wildlife Service's Region 1 and the Malheur National Wildlife Refuge. The draft environmental assessment is available for public review and comment through Sept. 21. It can be found at http://www.nwp.usace.army.mil/environment/home.asp under "Current public notices and environmental assessments."