Caspian terns who are scheduled to be relocated from the dredge material augmented island to locations in southern Oregon and northern California ate about 5 million salmon and steelhead smolts this year compared some 22 million eaten by double-breasted cormorants.
The research was done by Dan Roby of the U.S. Geologic Survey’s Oregon Cooperative Fish and Wildlife Research Unit and Oregon State University and Ken Collis of Real Time Research, Inc. The research that has been done since the 1990s is funded by the US Army Corps of Engineers and the Bonneville Power Administration.
While it is quite natural for terns and cormorants and other birds to eat salmon and steelhead smolts, the presence of these birds in the numbers they are today present on East Sand Island is totally the responsibility of dredging activity in the lower Columbia River and deposition of dredging materials that augmented an island that was not formerly the nesting ground of these terns and cormorants. The tern colony first arrived in the 1980s, after we started depositing dredging material on East Sand Island. The birds left when vegetation grew up within the first year and they relocated on Rice Island farther upstream. The Corps and wildlife manager decided to move the tern colony back to East Sand Island because they believed the predation was too great at Rice Island on salmon and steelhead smolts. Cormorants started nesting on the island in 1989 and have grown in numbers ever since.
Clearly, this is one of the many ways mankind has manipulated nature with devastating unintended consequences and this needs to be corrected immediately. Trouble is, once several populations of wild birds find a great source of food and good nesting habitat it will be difficult to