Artificial islands comprised of Columbia River dredged materials perfect nesting habitat for the birds have been around since about 1930, yet it wasn't until 1984 that Caspian terns established a nesting colony there.
The Caspian tern management project also calls for establishing and/or restoring three alternative nesting sites in the San Francisco Bay area, where the OSU-led team also has a research crew.
The development of alternative habitat at Crump Lake continues and nearby Summer Lake will allow the Corps to reduce the tern nesting habitat at East Sand Island on the Columbia River in 2009 by one acre. The environmental impact statement calls for the reduction of one acre of habitat there for every two acres constructed elsewhere. Dorsey said the Corps plans to leave 1.5 to 2 acres of Caspian tern nesting habitat on East Sand Island enough to support a colony about one-third to one-half the size of the current colony.
Ultimately, Dorsey said, East Sand Island could be an acre to an acre-and-a-half of nesting habitat under the final management plan if sufficient habitat is constructed elsewhere.
Redistributing terns is not without risk, Roby says. When researchers helped establish the new colony on East Sand Island, they were not certain the colony would thrive and they were unsure whether the move would reduce the birds' reliance on young salmon as a food source. The terns also required some protection from predators; an estimated 200 gulls, a more abundant species, were shot during the first two years at the East Sand Island tern nesting site.
"Officials from the National Audubon Society's Seabird Restoration Program told us we'd probably have to initially conduct some lethal gull control," Roby said, "or the gulls could prevent the tern colony from becoming establi
|Contact: Dan Roby|
Oregon State University