The US Army Corps of Engineers have killed nearly 3,000 double-crested cormorants and destroyed over 1,000 nests since last spring, in an attempt to protect salmon and steelhead in the Columbia River Estuary. This controversial practice is the Corps’ response to an overgrown colony of cormorants on East Sand Island who collectively consume as much as 15% of young salmon in the Columbia River.
Bob Winters, Cormorant Project Manager for the Corps, said, “It’s a complicated issue to which there’s no easy answer. Basically the Corps is trying to balance a need to improve juvenile salmon survival while maintaining a sustainable population of cormorants.”
Dan Roby, a professor in the Department of Fisheries and Wildlife at OSU, has been studying double-crested cormorants in the Columbia River Estuary since 1997. Before the cormorant culling began in 2016, Roby and his research group were working alongside the Corps to determine an effective management plan for the cormorant colony.
“We assumed, until the Corps told us otherwise, that the object was to reduce the size of the cormorant colony, given its impact on salmon and steelhead survival, but to do it in a primarily nonlethal manner,” said Roby.
He and his team previously assisted in the successful management of another bird species, Caspian terns, in the area by simply relocating the colony to an area where terns were focused less on salmon and steelhead as a major part of their diet.
“The Corps decided that the nonlethal approach was not going to be workable, so they made the decision to remove OSU and me as a representative of USGS from the working group that was trying to come up with a management plan for the cormorant colony,” added Roby.
Ultimately, the Corps plans to shoot 11,000 adult birds and oil 15,000 nests – destroying eggs and reducing the colony to less than half of its original size.
Joyce Casey, Portland Branch Chief for the Corps, said, “This is something we went in to with a lot of studying behind us, it’s not something we went in to lightly.”
However, Roby insists the Corps misconstrued data from his group’s previous research on East Sand Island to justify their management plan: “We never viewed our work as providing support for a primarily lethal approach for managing this cormorant colony – that was something the Corps decided largely for political reasons.”
When the Corps made the decision to switch to a primarily lethal approach, they brought in USDA Wildlife Services to perform the culling activities. Roby added, “We thought we would be involved in the managing and the monitoring of the management but when the Corps made the decision to switch from primarily nonlethal approach to a lethal approach, that’s not in our area of expertise. We’re not in to ballistics or firearms or how to kill birds more efficiently.”
How has the culling affected the persisting cormorant colony?
During the first breeding season coinciding with culling, surveyors reported that all of the cormorant nests on the colony had been abandoned, resulting in total loss of cormorant eggs. Although the birds returned six weeks later after culling was suspended, the cause of nest abandonment was never determined according to the Corps Cormorant Management website.
When asked about ongoing consequences of killing cormorants, Roby replied, “The Corps has awarded that research to a private consulting firm where they can control the message more easily than they can with us.”
By Keely Corder