A New Record for Bird Migration

Sooty Shearwaters travel farther than any animal ever tracked

Sooty Shearwater by Katherine A. Smith

www.elucidationimages.com

The bird world has a new champion of long-distance migration. Researchers have discovered that the Sooty Shearwater, a small seabird, travels about 40,000 miles every year, twice as far as the estimated journey for an Arctic Tern, which is often said to have the longest migration of any bird.

Led by Scott Shaffer at the University of California, Santa Cruz, the research team used devices called geolocating tags to collect information about the locations of shearwaters migrating over the ocean. They found that the birds traversed the entire Pacific Ocean in a figure-eight pattern, ranging as far north as the Bering Sea and as far south as Antarctica. The birds traveled farther than any animal scientists have ever tracked.

The study began on New Zealand?s Codfish and Mana islands, where the researchers captured 33 shearwaters in their underground breeding burrows. They affixed a geolocating tag to the leg of each bird, then set the birds free. As the birds flew, the tags recorded data that allowed researchers to determine each bird?s migratory path as well as the temperature of the water and the diving depth of the birds as they foraged for fish, squid, and krill.

The lines on the map indicate the long-distance movements of a breeding pair of shearwaters from their breeding colony in New Zealand to different wintering locations.

Courtesy of PNAS

The researchers recovered 19 tags when the shearwaters returned to their breeding colonies the following year. They found that the shearwaters had traveled different paths, initially going east from New Zealand, then north to the coast off Japan, Alaska, or California. After about five months in these widely separated wintering areas, the birds moved south again, crossing the equator within five days of each other.

The study revealed that the shearwaters traveled about 500 miles a day during migration. They seemed to have a strong preference for cool waters with a presumably abundant food supply. The tags recorded the birds diving as far as 200 feet below the ocean?s surface.

The authors noted that Sooty Shearwater populations are declining, both in the Southern Hemisphere, where they breed, and in the Northern Hemisphere, where they winter. They hope that studying the behavior of Sooty Shearwaters at sea will help reveal the causes of decline, which could include impacts from fisheries and global climate change.

—Sam Crowe, editor of the All About Birds web site www.allaboutbirds.org

For permission to reprint all or part of this article, please contact Laura Erickson, editor, Cornell Lab of Ornithology, 159 Sapsucker Woods Rd., Ithaca, NY, 14850. Phone: (607) 254-1114. email: lle24@cornell.edu