Tern Management Plan
by Bill Rudolph
The US Fish and Wildlife Service has released a draft environmental impact statement that weighs options for managing the huge number of Caspian terns, nearly 10,000 breeding pairs, about 70 percent of the West Coast population, that nest annually at the mouth of the Columbia River and feast on large numbers of juvenile salmon, including some listed for protection under the ESA. The document is part of a settlement of a lawsuit filed by bird lovers after the Corps of Engineers took actions to move the population further downstream from an earlier nesting site at Rice Island where the birds' diet was made up of more salmonids.
Through a combination of measures, the terns were encouraged to move downstream to East Sand Island, where their diet was less dependent on young salmon and steelhead. But plaintiffs in the lawsuit, the National Audubon Society, Defenders of Wildlife, Seattle Audubon Society and the American Bird Conservancy weren't satisfied with that action.
Government biologists say there are two reasons to reduce the numbers of terns on the Columbia by spreading them out. First, it would reduce predation on salmonids. And secondly, if the tern population was less concentrated, it would reduce the possibility that a large portion could be harmed by "storms, predators, human disturbance and disease."
A NOAA Fisheries report released in June says that terns nesting on East Sand Island eat more steelhead than salmon, by far. Government researchers estimated that in 2002 , the terns ate nearly 800,000 steelhead, about 6 percent of the run.
The management alternative preferred by the feds calls for reducing tern nesting habitat on East Sand Island and re-distributing most of the birds throughout the Pacific Coast. They say by doing nothing, the current nesting habitat would be fully "vegetated" within the next three years, a condition unsuitable for the nesting birds. The government says the terns would likely abandon the colony at that time.
If the colony was reduced by about two-thirds, scientists estimate that the population growth rate of all ESA-listed Columbia Basin steelhead stocks would increase by one percent or more, with initial benefits realized six to seven years after the project begins.
The draft EIS says the projected improvement in steelhead population growth rate is similar to increases that would result from hydropower improvements (0-4 percent), but well below the 4 to 8 percent increase that could occur from harvest reduction.
"Cumulatively," says the EIS, "the variety of salmon recovery actions have the potential to influence population growth rate to a substantially greater degree than would be realized from solely reducing predation from avian predators in the Columbia River estuary."
The draft EIS also say if measures taken to transplant most of the terns don't work by 2008, then a lethal control program would be instituted to reduce the population by 50 percent.
In any case, the plan calls for the Corps of Engineers to continue harassing birds at upriver nesting sites, and issuing egg-take permits at upper estuary islands if non-lethal efforts to reduce bird numbers fail. The Corps would also resume disposing of dredge spoils on the downstream end of Rice Island, site of the former colony.
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