How did a tiny electronic tracking device find its way from the inside of a Columbia River steelhead to the stomach of a flightless bird off the coast of New Zealand? It’s a question that has experts scratching their heads and doing what scientists do best—making educated guesses.
The Seattle Times reports that in April, bird researcher Dale Whaitiri was on an island off southern New Zealand examining the stomach contents of a baby sooty shearwater—a native seabird–when a tracking device the size of a grain of rice spilled from the bird’s gullet.
It was later discovered that the tag was originally placed in a juvenile steelhead in 2005 above the Bonneville Dam in the Pacific Northwest.
But the sooty shearwater chick examined by the researcher was too young to fly—let alone eat fish. Further, when steelhead enter the Pacific, they head north, not south. And the tags don’t float, they sink.
So how did the tag end up inside a flightless bird on the other side of the world, some 7,700 miles from where it originated?
“The odds are almost impossible to fathom,” Jen Zamon, a seabird expert for the Northwest Fisheries Science Center told the Times’ environmental reporter after learning of the discovery.
It seems that gull-like shearwaters are known to frequent the mouth of the Columbia during the summer months, returning to the southern hemisphere around October.
The answer to the mystery, at least to Zamon, is elementary. A sooty shearwater ate the steelhead on the Columbia, carried the indigestible tag in its stomach for two years, and then regurgitated it into its chick’s open beak.
But, she admits, that’s only speculation.
“Who knows?” she said.
Only a regurgitating sooty shearwater could answer that question.