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.
Today, 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.
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.
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 risk the cormorant population as a whole.
The Corps is taking public comments on the proposed management plan. It will hold several public meetings and webinars in July to take comments.