EAST SAND ISLAND, Oregon—Alexa Piggott is crawling through a dark, dusty, narrow tunnel on this 62-acre island at the mouth of the Columbia River. On the ground above her head sit thousands of seabirds. Piggott, a crew leader with Bird Research Northwest, is headed for an observation blind from which she'll be able to count them.
It's September, and the low-lying island is relatively quiet. Most of the fledglings and their parents have left, and only a few thousand pelicans and cormorants remain. But in the spring, 60,000 birds come here to nest. East Sand Island is home to the largest breeding colony of Caspian terns in the world and the largest colony of double-crested cormorants in North America—nearly 15,000 pairs.
That's too many cormorants, says the U.S. government. Starting next spring, it proposes to shoot more than half of the iridescent black birds, on the grounds that they're eating too many fish.
The cormorants eat mostly anchovies—but they also dispatch as many as 20 million salmon and steelhead trout smolts every year. The nesting season of double-crested cormorants on East Sand happens to overlap with the migration of the juvenile fish down the Columbia to the Pacific.
"They're eating over 6 percent of all the wild steelhead that are passing through the lower Columbia River," says Ritchie Graves, a fisheries biologist with the National Oceanic and Atmospheric Administration. They also consume more than 2 percent of the yearling chinook salmon.
Besides being commercially valuable, both fish are on the Endangered Species List, and that's what's forcing the U.S. Army Corps of Engineers to act. The corps owns and manages East Sand Island; indeed, it created the bird colony when it expanded the island with dredging spoils back in the 1980s.
Last summer the corps announced a proposal to kill 16,000 double-crested cormorants on the island over a period of four years. It also proposes to remove enough sand to inundate the nesting area of the cormorants, so that birds that leave won't come back. The goal is to reduce the double-crested cormorant population on East Sand Island to about 5,600 breeding pairs.
The move is part of a growing trend toward what wildlife managers sometimes call "lethal control"—killing one species of animal to protect another.
Lethal control of natural predators "is slowly becoming a dominant conservation strategy," says Michael Nelson, a professor of environmental ethics and philosophy at Oregon State University, in Corvallis. "We are embracing this as the first line of defense."
As the strategy is playing out at local levels, it is drawing opponents. That includes Piggott, who is dismayed by the corps' plan to shoot cormorants.
"We have built a level of trust between the researchers and the birds that nest around the blinds," she says. "It makes me sad and angry that we are breaking this relationship and using the blinds against the birds. They have no idea what's coming."
Picking Species to Save
For most wildlife managers, lethal control is probably an uncomfortable choice, but it's one they're finding themselves forced into more often these days—forced by humanity's expanding impact on nature to meddle with it some more. "With society having a bigger and bigger footprint, [the practice of lethal control] can only increase," says Michael Scott, an ecologist at the University of Idaho, in Moscow.
Climate change, which causes animals to move into new ranges and interfere with one another in new ways, can only exacerbate the dilemma, says Bob Sallinger, conservation director of the Audubon Society of Portland. "How much manipulation of these species do we want to do to protect one from another?" Sallinger asks.
We already do quite a lot. Starting in the 1970s, thousands of brown-headed cowbirds were killed in Michigan to keep them from invading the nests of endangered Kirtland's warblers. Last year the U.S. Fish and Wildlife Service began killing up to 3,600 barred owls in Washington, Oregon, and northern California to save northern spotted owls.
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In Idaho and Nevada, meanwhile, human encroachment on sagebrush habitat has boosted populations of the common raven at the expense of the imperiled greater sage-grouse. In a landscape devoid of tall trees, power line and communication towers now provide perches from which ravens can swoop down on sage-grouse nests and eat the eggs.
"When you put a tall structure in the environment, you have just provided a very strong advantage to that predator in finding its prey," says Peter Coates, a research wildlife biologist with the U.S. Geological Survey. The state of Idaho is now considering poisoning thousands of ravens to reduce the pressure on the sage-grouse.
In Alberta, woodland caribou and wolves rarely crossed paths until pipelines and logging roads made it easier for wolves to infiltrate caribou country. Since then, most of the caribou herds in the province have dramatically declined.
"We are at a turning point, where without some aggressive help in the next few years, we don't have much hope of keeping any of the herds around," warns biologist Stan Boutin of the University of Alberta, in Edmonton. In the past five years, hundreds of wolves have been killed to save one of the Alberta herds, known as Little Smoky.
Wolves themselves were almost eliminated from the United States until they received protection under the Endangered Species Act. As wolf populations recover and create new conflicts with human activities, says the University of Idaho's Scott, the animals have been allowed to occupy less than 5 percent of their historical range.
"That is the story that is playing out," Scott says. "How much is enough? How much are we willing to give up to nature?"
In the case of cormorants, it seems, not so much. In the eastern United States, double-crested cormorants have often been blamed for declines in fish populations. More than a half million birds have been destroyed under two different "depredation" orders since 1998, reports Linda Wires, author of The Double-Crested Cormorant: Plight of a Feathered Pariah.
In Oregon, the conflict between double-crested cormorants and salmon goes back to the hydropower dams on the Columbia, which interfered with fish migration.
"The cormorants were there long before the dams were, and they coexisted perfectly fine with the fish," says Sallinger. "It's the dams and the habitat destruction that have truly brought things out of whack. "
The Army Corps of Engineers has a long history with the problem on the Columbia-and not just with cormorants. Caspian terns also eat a lot of young salmon. In the 1980s the corps actually relocated an entire colony of terns to East Sand Island from Rice Island, another dredge—spoil island 16 miles (26 kilometers) upriver.
The expectation was that the birds would eat fewer salmon at the downriver location. That's not what happened, and the corps has since tried to move part of the East Sand tern colony to newer man-made islands in Oregon and northeastern California.
Why not move the cormorants too, opponents of the culling plan ask? "We don't want to just move the problem somewhere else in the region where the cormorants would begin to prey on other endangered fish," says Joyce Casey, chief of the corps' environmental resources branch in Portland. The Caspian terns, she explains, are "more amenable to our manipulation," whereas with cormorants, "we can't tell the birds where to go."
Faced with that uncertainty, the corps considers killing the cormorants the least risky solution—as well as the cheapest and quickest one.
Daniel Roby of Oregon State University, who has studied the impact of birds on salmon around East Sand Island for the past 18 years, disagrees: "We know enough about cormorant behavior that we think we can predict where the birds would show up."
Roby thinks the East Sand cormorants could be dispersed by restricting their nesting habitat. He and his team have done experiments in which they allowed cormorants to nest only in a fenced area and actively hazed and destroyed the nests of birds that settled outside the fence. "There are ways of resolving this issue that don't involve scapegoating the birds," he says.
A Beleaguered Population
Though the East Sand Island colony of double-crested cormorants has grown exponentially in recent years, the overall population in western North America is an order of magnitude smaller than the ones in the interior and eastern United States. From British Columbia to southern California there are only 31,200 breeding pairs. The proposed culling on East Sand Island would reduce the entire western population by 25 percent.
Other cormorant colonies in coastal Washington and British Columbia have been declining due to habitat loss, human disturbance, and predation by eagles. In British Columbia, double-crested cormorants have been designated a species of special concern. In California, the Salton Sea cormorant colony, the second largest in western North America, collapsed last year. "If you look at the current status of cormorant colonies in western North America, the future is not so bright," says Roby.
It's also not clear, opponents argue, that the culling would help the salmon and steelhead much. Other lethal removal programs in the region have yet to demonstrate success.
In recent years, for instance, California sea lions have been swimming 145 miles up the Columbia River to the Bonneville Dam, where they prey on chinook salmon that crowd around the fish ladder on their way upstream to spawn. Wildlife managers first tried to scare away the sea lions. But since 2008 they've killed 70 of the animals.
Now fewer California sea lions are showing up at the dam—but more Steller sea lions, which also eat salmon, are coming in. "Things would probably be worse without the program, but it is not the silver bullet," says Robert Stansell, a fish biologist with the Army Corps of Engineers. This particular population of Steller sea lions was taken off the Endangered Species List just last year. So far no one has proposed killing any of the ones at Bonneville.