ASTORIA, Ore. (CN) – The federal government killed thousands of double-crested cormorants in Oregon between 2015 and 2017, and may have caused the collapse of the birds’ largest breeding colony in a bungled effort to help young salmon make it to the ocean alive. Meanwhile, state biologists say the birds just moved upriver – where each eat three times as much salmon.
Government agencies have been on the offense to protect salmon by killing their natural predators. Sea lions and Caspian terns have been recent targets, and gulls may soon be added to the list. But what happened with cormorants has raised doubts as to the wisdom of the plan.
James Lawonn, Oregon Department of Fish and Wildlife biologist in charge of avian predation, says his agency “expects little to no gain in survival” for young salmon swimming through the Columbia River estuary with the federal management plan.
That’s because the overall number nesting along the Columbia River may end up being nearly as high as the average number that nested on East Sand Island. And while cormorants that live closer to the ocean choose from an extensive menu of ocean fish that school in the Columbia estuary, including anchovies, herring and smelt, upriver they eat a far higher proportion of salmon and other freshwater fish.
In 2017, most of the colony fled the island in what the Audubon Society called a “catastrophic collapse” of the largest population of double-crested cormorants in the world. The mass exodus came in the middle of the U.S. Army Corps of Engineers’ project to shoot thousands of birds out of the sky, destroy their nests and set off explosives on the island. Now, cormorant colonies are growing at a handful of spots miles upriver from the island – though the Corps notes no direct evidence linking its activities to the move.
Bob Sallinger, director of conservation for Audubon Society of Portland, says the plan failed birds, fish and taxpayers.
“We think this goes down as one of the really significant failures in wildlife management in recent decades,” Sallinger said. “It’s without question one of the worst things I’ve seen in my 25 years of wildlife advocacy.”
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Native to the West Coast, double-breasted cormorants love salmon. Their sleek, dark bodies dive and dart through the water, where they can remain submerged for over a minute before popping out with a fish in their bright blue mouths. They flourished on East Sand Island, named for the tons of sand dredged and dumped there by the Corps, and the island became their largest breeding colony.
After realizing it had inadvertently created an ideal habitat for seabirds, the Corps decided the surging cormorant population threatened the 120 million young salmon that swim through the estuary each year on their way out to the Pacific – some of which are federally listed as threatened or endangered. In 2015, the Corps partnered with other federal agencies to reduce the population from 12,150 breeding pairs, which it estimated ate an average of 12 million young salmon each year, down to 5,600 pairs by 2018.
The effort resulted in the death of 5,576 adult cormorants and destruction of 6,181 nests on the island. The Corps also used human patrols to harass adults into establishing their nests elsewhere.
The Corps planned to kill as many as 11,000 adult cormorants, but stopped when the colony fled the island in 2017. Only 544 breeding pairs returned to the island to nest, and in 2018 preliminary data from the Corps showed 3,672 active double-crested cormorant nests on the island.
While some cormorants will return to the island, many will be forced to go elsewhere: The Corps plans to convert most of the island into wetlands cormorants won’t choose for nesting. A sliver of rocky upland habitat the birds like along the island’s western beach will be left, and the Corps will remove eggs from any nests found outside that.
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