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.”
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.
The estimated 16,000 birds that fled the island in 2017 weren’t tagged or radio-collared, so there’s no data on where they went. But a sudden surge in cormorants nesting upriver has occurred since.
The Astoria-Megler Bridge stretches four miles to span the mouth of the Columbia at the state line. Cormorants have nested there since 2004, but only in very small numbers – until the Corps started killing and harassing birds on East Sand Island, seven miles away. Now there are 1,750 breeding pairs on the bridge and based on available habitat, the colony will likely double.
Other spots upstream have become new homes for 750 breeding pairs.
Between the birds the Corps will allow back onto East Sand Island and those settling at the Astoria-Megler Bridge and elsewhere, the state says there could soon be 10,000 nesting pairs in the Columbia River estuary – close to the original average of 12,000 pairs on East Sand Island before the Corps’ project.
But there’s a major difference: Each cormorant nesting upriver likely eats three times more young salmon than a East Sand Island cormorant based on data from Caspian terns living on Rice Island, 17 miles up the Columbia from East Sand Island. In 1999, the Corps moved an entire colony of Caspian terns, another fish-eating seabird, from Rice Island to East Sand Island. The Corps’ rationale? Birds on East Sand Island eat fewer salmon than those living upriver.
Dan Roby, a professor of wildlife ecology at Oregon State University, was hired by the Corps during the planning phase to study the potential effects of chasing cormorants off East Sand Island.
“If there’s a place in the Columbia River estuary where it would be best for cormorants to nest – and by best, I mean their effect on salmon and steelhead survival – it would be East Sand Island,” Roby said.
The Oregon Department of Fish & Wildlife is now assessing the impact of new colonies of cormorants on the survival of young salmon, after having warned the Corps its plan was likely to backfire.
In an agency comment on the Corps’ 2015 decision to implement the plan, the department warned the plan chosen was the most likely out of the five potential options to be a “major driver” of the redistribution of the cormorant population to other areas along the Columbia River. If that happened, the department said, it would “result in increased impacts to juvenile salmonids in Oregon.”
The state believes this is a federal problem.
“Because dispersal from East Sand Island was a significant possibility in our eyes, we did and do think that there’s a federal responsibility to address unforeseen impact to salmon that might have occurred as a result of management,” Lawonn, of the state’s Fish and Wildlife Department, said.
For its part, the Corps blames the birds’ mass abandonment of the island on eagles. Kris Lightner, the Corps’ biologist in charge of the project’s compliance with the National Environmental Policy Act, said she doesn’t know whether the increased numbers of birds upriver came from East Sand Island.
“There are more birds at the Astoria-Megler Bridge, but I don’t think anybody can say and back it up with data that the birds are dispersing in reaction to our management,” Lightner said. “The management plan has been very successful in reducing the amount of salmon eaten by birds on East Sand Island. We just don’t know about the estuary as a whole.”
The Corps plans to synthesize all the information it has collected over the last 20 years on birds that prey on salmon, but says data about birds on the bridge might not be included. The Corps also hasn’t decided if it will formally count the cormorants that nest there this year, according to Jake MacDonald, fish passage scientist with the Corps.
“We do not know yet if we are going to be monitoring birds on the Astoria Megler Bridge,” McDonald said. “That’s one of the areas that’s outside the Corps’ authority to do anything about. So the question becomes, do we monitor something we are not going to be able to act on?”
Sallinger of the Audubon Society, says targeting cormorants was just a way for the Corps to avoid addressing the number one killer of salmon: The network of dams in the Columbia River watershed.
“This was never about protecting salmon,” Sallinger said. “This was always about scapegoating birds to avoid the real challenges the corps needs to face up to. And the result has been a stunning failure, whether you care about birds or fish.”