The Art of Relocating Tern Colonies

To: Birding Aus <>
Subject: The Art of Relocating Tern Colonies
From: Laurie&Leanne Knight <>
Date: Sat, 24 Aug 2002 20:00:04 +1000
A news item off the wires for wildlife managers and ternaphiles ...


By Andy Duncan, 541-737-3379 
SOURCE: Dan Roby, 541-737-1955 

CORVALLIS - Marine birds called Caspian terns are not only eating fewer young
coho salmon, fall chinook salmon and steelhead but are raising more young of
their own successfully since humans encouraged the birds to switch nesting sites
in the Columbia River, scientists from Oregon State University and several
public and private organizations reported today (Aug. 9) in a scientific

The article, in the latest issue of the international Journal of Wildlife
Management, reports on the dietary and productivity effects of relocating about
9,000 pairs of the birds, the world's largest breeding colony of Caspian terns. 

The relocation effort grew out of concerns about juvenile salmonids (salmon-like
fish) eaten by Caspian terns when the birds nested on Rice Island, about 21
miles from the mouth of the Columbia River. The fish pass by the island during 
migration to the Pacific Ocean. 

Studies in 1997 and 1998 suggested that Caspian terns in the Columbia River
estuary, particularly those nesting on Rice Island, were consuming millions of
juvenile salmonids, including significant numbers of fish listed under the
federal Endangered Species Act. The relocation attempt, initiated in 1999,
centered on East Sand Island, about 15 miles closer to the mouth of the

Workers moved vegetation and debris to create more desirable bare sand nesting
habitat, installed tern decoys and playing recordings to attract terns, and
discouraged seagulls from eating tern eggs and chicks, said Dan Roby, a federal
wildlife ecologist based in OSU's Department of Fisheries and Wildlife who
helped plan the effort and coordinated the study of its effects. 

In addition, they disrupted tern nesting on Rice Island with tactics such as
planting wheat and installing fencing. The impact on young salmon was dramatic,
say the scientists. 

"In 1999 and 2000 the diet of terns nesting on Rice Island consisted of 77
percent and 90 percent juvenile salmonids, respectively," reports the journal
article, "while in 1999, 2000 and 2001 the diet of terns nesting on East Sand
Island consisted of 46 percent, 47 percent, and 33 percent juvenile salmonids, 

The researchers speculate that a key reason for the terns' new diet was the
greater variety of food available nearer the mouth of the Columbia River. 

The birds are consuming more marine forage fishes such as herring, sardines,
anchovies, smelt, surf perch and Pacific sand lance, according to the report. It
also says the nesting success of Caspian terns has been "consistently and
substantially higher on East Sand Island than on Rice Island." 

Rice Island was created artificially from dredge wastes. East Sand Island is a
natural island. 

Organizations participating in the Caspian Tern Working Group that did the
relocation work included the National Marine Fisheries Service, the U.S. Fish
and Wildlife Service, the U.S. Army Corps of Engineers, the Oregon and
Washington Departments of Fish and Wildlife, the Idaho Department of Fish and
Game and the Columbia River Inter-Tribal Fish Commission. 

The authors of "Effects of Colony Relocation on Diet and Productivity of Caspian
Terns," the article in the Journal of Wildlife Management, are: Dan Roby, Don
Lyons, David Craig, Anne Mary Myers and Robin Suryan of the Oregon Cooperative
Fish & Wildlife Research Unit at OSU; Ken Collis of Real Time Research, Bend;
and Jessica Adkins of the Columbia River Inter-Tribal Fish Commission, Portland.

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