The Common Shearwater, Nature's Migration King
ALEX CHADWICK, host:
The next time you're whining about that long commute, bear in mind a common seabird known as the sooty shearwater. From the time it departs nest to its return, the average shearwater soars 40,000 miles over the ocean. Forty-thousand miles. Honey I'm home. Here's NPR's John Nielsen.
JOHN NIELSEN reporting:
Sooty shearwater's are small dark birds with wings that look a bit too big for their bodies. As seabirds go, they're numerous but relatively inconspicuous, unless you happen to be standing on the rocky shore of Codfish Island off the coast of New Zealand at about the time of year when the shearwater's come home to breed in shallow tunnels.
Scott Schaefer (Ornithologist, University of California, Santa Cruz): So it's quite spectacular, especially when they come back from sea, when they all come into - flying into their burrows at night - you just see clouds of them hovering the island.
NIELSEN: Scott Schaefer is an ornithologist with the University of California at Santa Cruz. In a recent issue of the proceedings of the National Academy of science, he bestowed an unexpected honor on the sooty shearwater. The longest migration ever measured by science. Schaefer says the average length of one of these migrations is 40,000 miles, or to put it metrically, 30,000 kilometers each way.
Mr. SCHAEFER: I think it's 15,000 kilometers around the earth, so they do that twice - you could almost think of it that way.
NIELSEN: Schaefer and some colleagues captured 19 sooties on Codfish Island a few years ago. Then they tagged each bird with a lightweight tracking gizmo that takes location readings once a day. Eight months later the team re-captured the birds when they returned to Codfish Island. The information gathered by the tags showed that these birds were flying in giant figure eights back and forth across the Pacific Ocean. The migration started every April with a mass flight toward the West Coast of Chile, during which the sooties always flew less than a hundred yards above the surface of the ocean. That's where the waves bounce wind up into the air.
Mr. SCHAEFER: And create these updrafts. And that's how the birds are able to exploit the wind to make flying so cheap.
NIELSEN: Just before the sooties hit Chile, they land in the water and start chowing down on fish. Then after several weeks they take off again, heading northwest on trade winds. When the sooties reach Hawaii they start splitting up.
Mr. SCHAEFER: To California or Alaska, or they continue northwest to Japan.
NIELSEN: In all of these locations the birds come down to eat again, diving for anchovies, sardines, and squid. No one knows for sure why they end up where they do or whether certain birds return again and again to the same locations. The other thing nobody knows is why these birds all seem to turn around at the exact same time and head south in December.
Mr. SCHAEFER: Something in their brain signaled them, hey it's time to return home to breed. And fairly synchronously, all the birds travel through this corridor back to New Zealand within a 10 day period.
NIELSEN: From start to finish, it's an eight-month commute. Then four months later, after the breeding season is over, it starts again. Schaefer and his colleagues are now examining the links between this migration and the long-range travels of birds like albatross, fish like tuna, and ocean predators like sharks. Schaefer says he wouldn't be surprised to see the sooties loose their commuting title to one of these contenders soon. John Nielsen, NPR News, Washington.
CHADWICK: And stay with us on DAY TO DAY from NPR News.