The U.S. Army Corps of Engineers plans to kill nearly 16,000 cormorants nesting in the Columbia River estuary in an effort to protect threatened and endangered salmon and steelhead.
The corps issued its proposed management plan Thursday. It would wipe out about half the cormorants currently nesting on an island at the mouth of the Columbia River by 2018. Officials say it's the best way to reduce the colony to the number of birds required under an agreement that allows the Corps to operate dams on the Columbia River.
Scientists estimate cormorants on East Sand Island ate 18 million protected salmon and steelhead last year and are regularly consuming 10 to 15 percent of the populations swimming through the Columbia River estuary.
The biological opinion for the Columbia River hydropower system gives the Corps until 2018 to reduce 14,900 breeding pairs of cormorants down to less than 5,900 breeding pairs in order to preserve protected fish runs that also suffer impacts from dams.
On Thursday, the Corps released its preferred plan for reaching that target. In a draft environmental impact statement, the agency has proposed killing 20 percent of the colony every year from 2015 to 2018.
The birds would primarily be killed with shotguns. The plan would also use egg oiling -- stopping eggs from hatching by applying oil to them -- to kill 750 embryos of nesting birds.
Joyce Casey, environmental resources branch planning chief for the corps, said she's not aware of a time when the corps has killed so many birds.
"It's a very unusual action for the Corps," she said. "It is, however, part of our larger stewardship mission. We have a responsibility to all the species that depend on the Columbia River system. This is obviously a complicated issue. It gets at larger societal questions about managing competing uses of the river."
Casey said agency research has found that alternatives to lethal removal such as shrinking the birds' habitat hasn't had an effect on the number of birds nesting on the island.
"It hasn't had an effect on the colony size, and it hasn't had an effect of dispersing the birds out of the estuary," she said. "Our research shows the birds don't really like to leave the estuary. From a bird's point of view, East Sand Island and the Columbia River estuary are such a great place to be that's where they want to come and raise their young."
The Corps' environmental review found the proposed actions wouldn't jeopardize the cormorant population as a whole. In its environmental analysis, the Corps considered alternatives to lethal removal. One alternative would remove some eggs through oiling and rely primarily on non-lethal methods such as hazing and reducing habitat area to disperse the colony to other places. The agency concluded that the preferred option involving lethal removal would provide more certainty at a lower cost.
Columbia River tribes have expressed support for killing cormorants to protect salmon and steelhead. Blane Parker, a fishery manager and biologist with the Columbia River Intertribal Fish Commission, says the birds are eating juvenile salmon as they migrate out of the river into the ocean. That removes the potential for hundreds of thousands of fish to return to the river as adults that tribes would catch.
"The tribes have put forth a tremendous amount of energy and resources to recovering salmon in the Columbia River Basin," Parker said. "For these fish to have the benefits of retrofitted hydropower systems, increased quality of stream habitat, increased flows and to be eaten a few miles from the ocean is very disappointing and very frustrating for our rebuilding efforts."
Bird advocates have voiced opposition to the plan. Bob Sallinger of the Portland Audubon Society says he was hoping for a plan that put a higher value on the birds. Plus, he says many of the fish the birds are eating are not wild fish but have been produced in hatcheries.
"It's a critically important bird colony and killing 15,000 birds primarily to protect hatchery fish just is not an acceptable solution," he said.
The Corps is taking public comments on the proposed management plan. It will hold several public meetings and webinars in July to take comments.