In 2014, the U.S. Army Corps of Engineers released a draft Environmental Impact Statement and management plan to reduce predation of juvenile salmon and steelhead by double-crested cormorants in the Columbia River Estuary. In developing the plan, the Corps has worked closely with the following cooperating agencies: the U.S. Fish and Wildlife Service, the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service - Wildlife Services, the Oregon Department of Fish and Wildlife and the Washington Department of Fish and Wildlife.
East Sand Island's double-crested cormorant colony has grown from approximately 100 pairs in 1989 to 14,916 nesting pairs in 2013, which accounts for more than 40 percent of the western population. This breeding colony is the largest in North America.
The Corps has been conducting research studying the impact of avian predation on juvenile salmonids in the Columbia River Estuary since 1997. The research on East Sand Island contributes to understanding of the impacts cormorants have on juvenile salmonids migrating out to the ocean. Click here to see two graphics demonstrating the impact of the cormorant colony on East Sand Island to salmonids. The first graph shows annual consumption of juvenile salmonids by the colony. The second graph shows the seasonal proportion of salmon the double-crested cormorants consume during their nesting season.
In 2008, the Corps began small-scale management feasibility studies on the double-crested cormorant colony, restricting the birds from nesting in specific locations on East Sand Island. Study methods included hazing with lights, reducing nesting habitat and using human presence to flush double-crested cormorants off potential nesting sites.
In 2011, the studies focused on reducing the amount of available nesting habitat for double-crested cormorants on the western portion of the island and tracking the dispersal of radio- and satellite-tagged individual double-crested cormorants. Habitat reduction was primarily accomplished by installing barrier fences and using human hazers to flush birds from the non-designated nesting area.
In 2013, double-crested cormorants were restricted to 4.4 acres. Eighty-three adult double-crested cormorants were marked with satellite transmitters and several hundred adults were banded with leg bands to provide information about where double-crested cormorants would move during the dissuasion efforts. Although reduced by 70 percent, available habitat was not completely limited and 14,900 breeding pairs ultimately nested on the island. Near-term dispersal locations of radio and satellite tagged double-crested cormorants during the 2011–2013 breeding seasons were generally to four main areas identified in geographic proximity to East Sand Island:
- Columbia River Estuary (defined as the tidally influenced 172 river miles from the mouth of the Columbia River to Bonneville Dam, including the Willamette River down to Willamette Falls Locks)
- Outer Washington coast (Willapa Bay and Grays Harbor)
- Puget Sound
- Northern Salish Sea (San Juan Islands, Strait of Georgia, Vancouver, BC) (BRNW 2014).
Of these areas, the Columbia River Estuary has had the highest levels of use by double-crested cormorants during the dissuasion research in 2012 and 2013. There were no confirmed detections of radio- or satellite-tagged double-crested cormorants at inland sites east of The Dalles Dam, or at coastal sites south of Cannon Beach, Oregon.
In 2015, the Corps prepared a final Environmental Impact Statement and has made the document available for public review. Brig. Gen. John Kem, the U.S. Army Corps of Engineers Northwestern Division commander, signed a record of decision for the Double-Crested Cormorant Management Plan Final Environmental Impact Statement March 19, 2015. The ROD documents Kem’s decision and rationale for adopting the management plan to reduce predation on juvenile salmon and steelhead listed under the Endangered Species Act by a growing population of double-crested cormorants in the Columbia River estuary.
The Corps selected alternative C-1 in the final EIS, to carry out actions in the management plan. In phase one, actions would include culling individuals and oiling eggs to achieve a colony size of about 5,600 breeding pairs by 2018. In phase two, the western portion of East Sand Island would be inundated to preclude nesting, and the Corps would continue monitoring and hazing efforts. If needed, limited egg take would continue as well.
Alternative C-1 uses adaptive management methods to determine the following year’s actions. We will work with the U.S. Fish and Wildlife Service’s migratory bird team when developing each year’s actions. The team will analyze the long-term sustainability of the double-crested cormorant colony at East Sand Island and the western population. The number of individuals culled and eggs oiled in each year will be based on the team’s analysis.
To carry out the actions in the plan, The Corps of Engineers applied for and was granted a depredation permit from the U.S. Fish and Wildlife Service. The permit allows the Corps to cull a specific number of individual adults and oil a specific number of eggs to meet the plan’s goals. The Corps must apply for a depredation permit each year.
Site preparation for management actions was completed on East Sand Island by mid-April. This included placing fencing to minimize disruption of other bird species also found on the island and help minimize disbursing the birds to other island and off-island nesting locations. The fencing also facilitates counting and tracking of the bird population.
The Corps released its final Environmental Impact Statement on Feb. 6, 2015.
Brig. Gen. John Kem, the U.S. Army Corps of Engineers Northwestern Division commander, signed a record of decision for the Double-Crested Cormorant Management Plan Final Environmental Impact Statement March 19, 2015.
The Corps requested and received a depredation permit from the U.S. Fish and Wildlife Service on April 13, 2015. The permit allows the Corps to cull a specific number of individual adults and oil a specific number of eggs to meet the goals of the plan. The Corps must apply for a depredation permit each year.