Mid-Columbia Efforts to Reduce Avian Predation
"Pretty simple actions," at the mid-Columbia Basin's Goose Island have produced "pretty dramatic results" in the effort to reduce avian predation on protected salmon and, particularly, steelhead that swim downstream through the Grant County Public Utility District's Wanapum and Priest Rapids dams and reservoirs, according to Grant's assistant general manager, Chuck Berrie.
Caspian terns nesting on Goose Island in Potholes Reservoir just east of the Columbia River in south-central Washington annually consume an average of 15.7 percent of steelhead smolts and 2.5 of the spring chinook smolts out-migrating from the upper Columbia River, according to research estimates. Both stocks include fish that are listed under the Endangered Species Act.
Such predation has made it difficult to for Grant PUD to meet its project-level juvenile steelhead survival standards despite having what the utility says is excellent "concrete survival" through the actual dams.
Monitoring and evaluation indicates that a new active-passive "dissuasion" strategy employed late last winter and into the spring at Goose Island did the trick, persuading all but three pairs of Caspian terns that visited the island from attempting to nest. A total of three eggs were laid, and those were removed by researchers. A total of 340 nesting tern pairs were identified in 2013, the second most of any site in the Columbia Plateau region.
Goose Island tern predation on steelhead was reduced from that 15.7 percent, five-year average, to only 2.9 percent in 2014. The chinook take dropped to 0.3.
"As a result we made our survival target," Berrie said. The survival through Grant PUD's Priest Rapids Project (Priest Rapids and Wanapum dams and reservoirs) was 89.3 percent in 2014 as compared to a target of 86.5 percent. The targets are conditions of the dams' federal license. Research conducted in 2008-2010 showed survival rates of 82.8 percent, 83.1 percent and 78.7 percent.
Operational adjustments and fish passage improvements completed in recent years have boosted survivals. Route-specific passage survival at dams during 2014 were at or near 100 percent through fish passage facility routes, 99.4 and 97 percent respectively through Wanapum and Priest Rapids spillways and 94.1 and 93.8 percent respectively through the powerhouse turbines.
"We've pretty much proven that it isn't at the concrete anymore," Berrie said of the immediate toll on juvenile salmonids.
Most of that 2014 predation likely was from the 159 terns that shifted to nearby Northwest Rocks, a Potholes high spot off the end of Goose Island that is no larger than the Northwest Power and Conservation Council's meeting room, said Grant's Curt Dotson. He and Berrie updated the Council's Fish and Wildlife Committee on Grant's evaluation of the "Efficacy of Management Actions to Reduce Caspian Tern Predation on ESA-listed Salmonids in the mid-Columbia Region."
Terns at Northwest Rocks raised 46 fledglings. There had been no known nesting at the site previously.
Goose Island is a 4.9 acre, steep-sided rocky island located near the southern end of Potholes Reservoir, near the City of Moses Lake (WA); it is owned by the Bureau of Reclamation and is managed in cooperation with the Washington Department of Fish and Wildlife. It is located roughly 30 miles from the Columbia River, directly east of the Wanapum Dam reservoir. Priest Rapids is downstream of Wanapum.
Dissuasion materials were delivered to Goose Island via helicopter just about a year ago (Feb. 25, 2014) The passive dissuasion involve construction with pier blocks, rebar, PVC tubing, polypropylene rope, and caution tape to cover 2.5 acres of tern nesting habitat.
Since Grant has no legal authority to manage/mitigate for impacts caused by the terns, the work was led by the U.S. Army Corps of Engineers and the Bureau. The Corps funded much of the construction for the project. Grant paid for much of the monitoring and evaluation through its $2 million no-net impact (on salmon and steelhead) fund. The licensing agreements spell out actions to be taken to mitigate for the two dams' impact on fish populations.
The overall plan -- to move birds and as a result reduce predation -- is called for in NOAA Fisheries' current biological opinion on operations of the Federal Columbia River Power System. The BiOp outlines measures NOAA Fisheries feels are necessary to mitigate for hydro system impacts on listed salmon and steelhead, and avoid jeopardizing the survival of those species. The Corps and Bureau, which operated dams in the system, are obliged as so-called "action" agencies to carry out mitigation actions.
Active hazing of gulls and terns was initiated last year at Goose Island in late March. Terns fly north in spring in search of choice nesting grounds where they are relatively safe from natural predators. They hatch out their young in springtime typically and depart in mid- to late summer.
"That is the 'push' part," said Dotson. The region as a whole is engaged in a push-pull strategy aimed at reducing avian impacts, and tern impacts in particular, on protected salmon and steelhead migrating down through the Snake and Columbia river systems toward the Pacific Ocean.
The Corps, which owns and operates eight dams on the lower Columbia and Snake, is leading the charge. It has been since 2008 involved in an effort to reduce available nesting habitat space (push) for terns at East Sand Island at the mouth of the Columbia, while constructing alternative nesting islands (pull). Those built-to-please tern islands include five in interior Oregon and three in northeastern California where predation on ESA listed fish is not believed to be an issue.
The annual East Sand tern colony is believed to be the largest in the world.
The "pull" part is still a work in progress. With the virtual elimination of tern habitat at Goose Island, tagged birds from that site were noted at salmon and steelhead-eating sites up and down the river, on Twinning Island in Banks near the mid-Columbia's Grand Coulee Dam and at Crescent Island downstream in McNary Dam's reservoir.
Berrie and Dotson noted that birds familiar with the Goose Island nesting area, once dissuaded, turned to other options in the region.
"We're seeing the first effect of pushing them out the door," Dotson said of the 2014 season in which many of the terns were ousted from familiar breeding grounds and forced to seek new roots elsewhere.
"Elsewhere on the Columbia Plateau, 474 breeding pairs attempted to nest on Crescent Island in the McNary Pool (21 percent increase over 2013; about 45 pairs nested on the Blalock Islands (John Day pool), about 67 pairs nested on Twinning Island (Banks Lake), and about 8 pairs nested on Harper Island (Sprague Lake). Productivity at both Crescent Island and Blalock Island colonies averaged 0.33 young/pair; both the Twinning Island and Harper Island colonies failed," according to a research abstract produced by U.S. Geological Survey, Oregon State University and private researchers. Productivity at Northwest Rocks was estimated at 0.29 young per pair.
Birds looking for other inland nesting refuges did not fare so well, according to the research led by the USGS-Oregon Cooperative Fish and Wildlife Research Unit's Daniel D. Roby.
"Interior Oregon and northeastern California were subjected to severe drought in 2014, with all Corps-constructed tern islands becoming land-bridged or nearly so before the end of the nesting season. Associated with the drought, mammalian predators were detected on all monitored islands at least once during the Caspian tern nesting season.
"A total of only 786 breeding pairs nested on five Corps-constructed tern islands in 2014, and average productivity was just 0.16 young per pair. The largest colony was at Sheepy Lake tern Island (520 pairs) and the most productive was at Tule Lake tern island (0.60 young per pair)." Sheepy Lake and Tule Lake are, respectively, in the Lower Klamath and Tule national wildlife refuges in northeast California.
"We need to build a new home for them," said Dotson. "That's the pull part." Next up are specifically prepared nesting areas in Don Edwards NWR in San Francisco bay.
Construction work was completed this week to elevate five islands in the south bay and apply substrate suitable for tern nesting in preparation for the terns annual northward flight. Many of the birds follow the Pacific coastline, so the Don Edwards alternative nesting sites are right in their migratory path.
The hope is that terns ousted from their accustomed northern nesting sites will investigate the Don Edwards terrain. Tern decoys and acoustic devices (social attraction) are being set up in hope of luring birds to the islands.
The refurbished Don Edwards islands represent 2.3 new acres of what is believed to be desirable tern nesting habitat.
"We have extremely high hopes for Don Edwards," said David Trachtenbarg, program manager and fisheries biologist with the Corps' Walla Walla District.
"It's exciting," the Bureau's Ann Haynes said of the work being done in the mid-Columbia region and at Don Edwards.
The work will continue this year at Goose Island, with an expansion to include Northwest Rocks. The same tactics will be employed this year at Crescent Island in what is a phase 2 of the Corps' Inland Aviation Predation Management Plan.
The plan is to move terns away from known salmon predation hot spots, and targets adaptive management actions to limit terns from forming new colonies and/or expanding existing colonies within the Columbia River basin. The plan includes provisions for developing out-of-basin Caspian tern nesting sites to attract terns to areas where they will not feed on Columbia River ESA-listed fish species.
In 2008, the Corps began implementing the plan "Caspian Tern Management to Reduce Predation of Juvenile Salmonids in the Columbia River Estuary," which seeks to redistribute a portion of the large East Sand Island tern colony to alternative colony sites in Oregon and California. Researchers estimate that in 2014 the 1.58 acres of East Sand Island habitat held about 6,630 breeding pairs, similar to 2012 and 2013.
Don Edwards NWR (Ponds N1-N9) is one of three sites in the San Francisco Bay area where resource managers plan to create or enhance nesting habitat for Caspian terns.
Berrie and Dotson deemed the 2014 dissuasion effort a qualified success, saying that an additional year or years of evaluation would be needed to verify the push success, and maybe many more years of evaluation and work needed to determine if displaced birds are relocating to those preferred alternative habitat sites.
"Efforts to prevent Caspian terns from nesting on Goose Island were only partly successful due to a colony that formed unexpectedly on Northwest Rocks," according to the Grant PUD summary.
"Management efforts on Goose Island demonstrated that dissuasion (passive & active) can prevent nesting by Caspian terns" and that "Predation on ESA-listed steelhead and spring chinook by Goose Island Caspian terns was significantly reduced in 2014 compared with pre-management estimates."
"Increased predation from Caspian terns nesting at nearby colonies (Banks Lake, Crescent Island) slightly offset benefits from a smaller Goose Island tern colony in 2014."
Research Tracks Movements, Steelhead Predation by Caspian Terns in Mid-Columbia Basin by Staff, Columbia Basin Bulletin, 1/3/14
Plan Set to Limit Mid-Columba Bird Predation by Staff, Columbia Basin Bulletin, 2/7/14
Final EIS Released on Reducing Estuary Cormorant Numbers; Proposes Both Shooting and Egg Oiling by Staff, Columbia Basin Bulletin, 2/6/15
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