Caspian Terns at Dungeness Spit

The U.S. Fish and Wildlife Service released a plan for dispersing the world’s largest colony of Caspian Terns from the mouth of the Columbia River to seven alternate sites in Washington, Oregon, and California.  It is aimed at reducing the number of young salmon eaten by terns.  The plan was prepared in cooperation with the U.S. Army Corps of Engineers and NOAA Fisheries, the federal agency responsible for recovering the 13 populations of salmon and steelhead in the Columbia River Basin that are listed under the Endangered Species Act as threatened or endangered. The complete plan can be found at migratorybirds.pacific.fws.gov/CATE.htm.

Sara Moculeski

The plan also benefits the terns by redistributing a large breeding concentration that leaves the population vulnerable to disease, human disturbance, predation and storms. Currently, about 70 percent of the entire western population of Caspian terns in North America nests on East Sand Island in the Columbia River estuary. Based on the average number of nesting pairs in the Columbia River estuary for 2000 - 2004 (approximately 9,175), about 6,000 to 6,675 breeding pairs will be dispersed to alternate sites while about 2,500 to 3,125 breeding pairs would continue to use East Sand Island.  

For every acre of tern nesting habitat eliminated on East Sand Island, the tern management plan calls for two acres to be created or enhanced at alternate sites along the Pacific Coast and in interior Oregon. Creation or enhancement of alternate sites would be completed by 2010. Tern nesting habitat on East Sand Island will not be reduced until nesting habitat at alternate sites is created or enhanced.  In all, about 8 acres of nesting habitat will be created or enhanced elsewhere and 1 to 1.5 acres will be maintained on East Sand Island.  All of the alternate sites are on public land and most already have some terns nesting.

The site proposed in Washington is at the Dungeness National Wildlife Refuge (Dungeness Spit) in Clallam County.

The first time that a tern nesting colony was seen at Dungeness Spit was in 2003. This is independent of any efforts by East Sand Island redistribution plan. In 2004, they returned, with the first one seen on March 23^rd. A small colony was observed on April 19^th, and the first egg at the colony was observed on May 10^th.

The unofficial end count of Caspian Terns on Dungeness Spit for 2005 was:

• 655 adults
• 459 chicks
• 109 chicks banded
• 28 failed nests
  

In addition, there were two Arctic Tern pairs that produced two chicks.

Background:

In 1999 and 2000, in a project led by the Corps of Engineers, the Caspian terns were relocated to East Sand Island from Rice Island, 15 miles up the Columbia River using the same strategies. While nesting on Rice Island, the terns’ diet consisted almost entirely of steelhead and salmon. On East Sand Island, near the mouth of Columbia River, the terns' diet shifted to mostly marine fish, such as anchovies. The number of young salmon and steelhead eaten by terns dropped by 52 percent. However, NOAA Fisheries scientists believe the large East Sand Island tern colony is still negatively affecting Columbia River salmon recovery because the number of smolts eaten by terns is substantial and is expected to increase as predicted poor ocean conditions result in fewer marine fish for the terns to eat.

The tern management plan was developed as part of a 2002 lawsuit settlement agreement between the Service and the Corps and the National Audubon Society, Defenders of Wildlife, Seattle Audubon Society and the American Bird Conservancy. In the settlement agreement, the agencies agreed to maintain six acres of habitat on East Sand Island near the mouth of the Columbia River until 2005, complete three studies and prepare a tern management plan and EIS for implementation in 2005.

The Caspian tern is a fish-eating bird that occurs worldwide and is native to the Pacific Northwest. The East Sand Island colony near the mouth of the Columbia River is the world's largest, with more than 9,000 pairs. Nesting by Caspian terns in the Columbia River estuary has grown significantly since it was first documented in 1984. Caspian terns have concentrated in the estuary because historic nesting sites have been lost elsewhere in the Pacific Coast/Western region and human-created dredge-spoil islands in the estuary offered stable nesting habitat close to abundant supplies of fish. Caspian terns typically nest in relatively small numbers (e.g., 100- 1,500 pairs) on islands along the coast and interior lakes. The concentration of about 70 percent of the regional tern population is an atypical occurrence for this species.