Caspian terns will be evicted from the Mid-Columbia's Goose and Crescent islands to protect endangered steelhead and salmon, under a new federal plan.
The Army Corps of Engineers and Bureau of Reclamation believe that if they can get the salmon-eating birds to stop nesting on the islands, they will find new nesting areas outside the Columbia River Basin.
The birds tend to travel long distances, according to a new federal report adopting the decision recommended in an environmental study.
Both islands are manmade. Goose Island is in Potholes Reservoir near Moses Lake, and Crescent Island, created from dredged material, is in the Columbia River about nine miles south of the confluence with the Snake River near Wallulla.
From 2007-09 about 370 pairs of terns nesting on Goose Island feasted on 14.6 percent of inland Columbia Basin steelhead, according to data collected from fish tags that litter the island after birds digest the fish.
In 2004, about 530 pairs of nesting terns on Crescent Island are estimated to have eaten 22 percent of the Snake River steelhead. The tern population there has since dropped to about 420 pairs.
The birds also eat juvenile chinook and sockeye salmon.
The Corps plans to start with a test planting of willows on Crescent Island to see if they will grow and reduce the open ground terns favor for nesting. They nest on islands to reduce their exposure to predators such as coyotes, weasels and rodents.
Temporary ropes hung with flags also could be set up to discourage nesting, particularly if birds try to relocate from Goose Island.
If more action is needed the second year, workers would chase the birds off daily from late February to early July and would flatten dirt scraped up on the ground for a nest.
Hazing will not be done in the first year of the program because gulls already might be nesting.
Should bad weather, such as lightning, prevent workers from hazing the terns and some eggs are laid, the eggs could be taken. However, the management plan expects that only a few eggs a year would need to be removed.
Long term, about 20,000 willow whips could be planted, initially protected with fencing from beavers that eat willow bark.
On Goose Island a network of ropes hung with flags is planned to discourage terns from nesting because rocky soil and a deep water table make planting vegetation impractical.
Birds also will be chased away from potential nest sites and eggs collected. Federal officials expect that no more than three or four eggs would need to be collected annually, although a permit would allow as many as 200 eggs to be collected in the area of the upper Columbia and Snake rivers.
If there are still attempts to nest on Goose Island after three years, cobble or boulders could be spread across the nesting area to make it unsuitable.
The plan to protect endangered fish species is based on an environmental study that focused on Goose and Crescent islands because of the many terns that nest there. But there are other islands where the birds could attempt to nest if they are driven away from current nesting sites. Those include Solstice Island in the Potholes Reservoir and Three-Mile Canyon Island.
Any potential nesting sites between the Bonneville and Wanapum dams, on the Snake River upstream to Lewiston and in the Potholes Reservoir, will be monitored by aerial surveys.
-- Annette Cary: 582-1533; firstname.lastname@example.org; Twitter: @HanfordNews