Scientists puzzled over fish tag that traveled 7,700 miles

Bird researcher Dale Whaitiri was on an island off southern New Zealand examining the stomach contents of a baby seabird when an electronic device the size of a grain of rice spilled from the bird's gullet.

The monitoring tag had been planted years before in a juvenile steelhead — on the Columbia River in the Pacific Northwest. But this chick was too young to fly — let alone eat fish.

The discovery has launched a tale of scientific intrigue spanning 7,700 miles across the Pacific Ocean. How did the tag wind up in a fat, flightless bird about to be eaten by Maori tribesmen? And of the millions of seabirds — called sooty shearwaters, or "titi" by the Maoris — how did Whaitiri manage to poke this one's belly?

"The odds are almost impossible to fathom," said Jen Zamon, a seabird expert for the Northwest Fisheries Science Center.

The story really began in 2005, when a Northwest scientist stuffed the puny tag into the steelhead, chucked it into the Columbia and watched the signal blip off the radar when the fish passed the Bonneville Dam on its way to sea that spring. But then what?

The little tags don't float. So it didn't drift to New Zealand to be eaten off the ocean's surface. Besides, sooty-shearwater chicks can barely move. They're often fatter than their parents, and they eat only when fed by adult birds.

The silver, bullet-headed steelhead of the Columbia River have been snared as far away as the Bering Sea. But they migrate north, not south.

"The fish didn't do the traveling," concluded Doug Marsh, a Seattle biologist for the fisheries science center, who learned last week that Whaitiri had found his fish tag in April.

"So it must have been the bird."

Actually, sooty shearwaters are no strangers to the Columbia River. They are known to travel tens of thousands of miles in search of warm weather, and often congregate at the river's mouth. Then they work their way north and west to Japan and south to New Zealand, where they nest high in the hills and lay eggs in underground burrows.

The native Maori catch the delicious chicks for supper, but hand over the stomachs to Whaitiri and other researchers who monitor the birds' diets.

So the answer may be elementary, Zamon said: A sooty shearwater ate the steelhead on the Columbia, carried the indigestible glass tag in its belly for two years, then regurgitated it into the baby's eager maw.

But that's merely an educated guess. For all she knows, the tag "could have been abducted by aliens or something," she kids. "Who knows?"

The mystery is a reminder of how much the northern and southern hemispheres are linked. And for the scientists, it raises other questions.

There are tantalizing ones: We know shearwaters eat lots of squid, but how much salmon and steelhead do they down?

And the silly: Given how many shearwaters traverse the continents, how many monitoring tags have been eaten by unknowing Maori?

"I'm sure that question is being asked in New Zealand right now," Zamon said.

The tags are harmless, and usually tucked into parts of fish that no one eats.

And if eaten by a human, a tag would just pass through. Right?

"There are rumors that some grad students have ... um ... done that," Zamon said.

"Good luck finding one who'll admit it."

Craig Welch: 206-464-2093 or cwelch@seattletimes.com