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The cooperation of many nations, and desire to protect these magnificent travelers, will be stronger....

Long-distance Migration Strategies

Nils Warnock, PhD


Researchers from several nations remove Dunlin from a "cannon" net. Photo by Nils Warnock

Many migratory shorebirds, though admittedly ignorant of our political boundaries, are experts in crossing international borders. In the spirit of international cooperation, I recently had the honor of joining a distinguished group of ornithologists from Sweden, the Netherlands, Germany, Australia, New Zealand, Canada, the United States, and other countries, in a major new research effort. We are combining resources to address, on a large scale, unanswered questions about shorebird migration and how to conserve these far-ranging species.

Our study sites dot the Yukon-Kuskokwim Delta (the delta), a huge triangle of land situated in northwestern Alaska between the Bering Sea and the Yukon and Kuskokwim rivers. Immense, flat, pond-studded tundra, the delta is one of the most important breeding and migration staging areas in the world for waterbirds, including such rarities as Spectacled Eiders, Aleutian Terns, and Bristle-thighed Curlews. We concentrate on four shorebird species--Dunlin, Rock Sandpipers, Bar-tailed Godwits, and Sharp-tailed Sandpipers--each of which has a fascinating story to tell.

Bar-tailed Godwits breed on the delta and also further north in the Arctic. Many embark on perhaps the longest non-stop migration of any bird--an energy defying, non-stop flight from the delta to Australia and New Zealand--up to 11,000 kilometers in five to eight days without landing.

Sharp-tailed Sandpipers breed in northern Russia. For some unknown reason, many thousands of birds, almost exclusively juveniles, migrate across the Bering Sea in late August and early September to feed and fatten on the delta before flying back across the Bering Sea, toward various areas of Australasia.
Dunlin. Photo copyright Arthur Morris/VIREO

Two subspecies of Dunlin use the delta. Calidris alpina pacifica breeds in western Alaska, including on the delta; stages there in the fall; then flies south to winter from the Pacific Northwest to Mexico. C. a. articola breeds in northern Alaska. Some of these birds come down to the delta in fall to stage before flying across the Bering Sea to winter in Asia.

Various subspecies of Rock Sandpiper breed in Alaska and stage at the delta in the fall. While some of these birds may migrate across the Bering Sea, most will spend their entire life in Alaska, enduring bone-chilling winters on the coast before returning to their tundra breeding grounds.

The complexity of migratory strategies used by these shorebirds makes them ideal candidates for study by our international group. Our team combines the resources of diverse individuals, organizations, universities, and agencies* and employs state-of-the-art techniques.

(*Among others: Swedish Polar Research Secretariat, U.S. Fish and Wildlife Service, U.S. Geological Survey, Netherlands Science Foundation, National Science Foundation, and PRBO Conservation Science.)

Using satellite tags and VHF radio transmitters to track individual Bar-tailed Godwits, Dunlin, and Sharp-tailed Sandpipers, we are answering questions about how individual birds use the delta, and how (and how fast) they migrate to non-breeding grounds. Using stable isotopes in feathers and DNA in blood, we investigate where the birds we are studying come from and where they go --and we monitor the potential spread of avian influenza.

Understanding what foods the birds use here to fatten up for migration entails taking thousands of invertebrate and seed samples from Bering Sea mudflats and tundra ponds. By banding and measuring thousands of birds, we accumulate data to answer such questions as how quickly birds are fattening for migration, how much fat they actually need to successfully migrate, and how their molt affects their migration decisions.

After two fall migration seasons, this group of international ornithologists will produce results that greatly add to what we know about the globe-crossing escapades of certain migrating shorebirds. The cooperation of many nations, and desire to protect these magnificent travelers, will be stronger as a result of new knowledge gained.