By RACHEL KAUFMAN - NATIONAL GEOGRAPHIC
Added: Sat, 14 Jan 2012 05:52:33 UTC

Tiger sharks preying on birds disoriented by oil-rig lights, research suggests.

A tiger shark (foreground) swims near the surface in the Bahama Islands.
Photograph by Brian J. Skerry, National Geographic

What's a songbird doing in the belly of a tiger shark?

The predators are eating land birds affected by offshore oil rigs in the Gulf of Mexico (map), according to new research.

Marcus Drymon, of Dauphin Island Sea Lab, has been studying fish off the Alabama coast since 2006. During a routine sampling in 2009, he pulled a tiger shark onto the deck of his boat to tag and release it.

"He coughed up some feathers," Drymon said.

That in itself wasn't unusual, he said. Tiger sharks in other parts of the world are known to eat marine birds. But once Drymon analyzed the feathers in the lab, he was fairly sure they had come from a terrestrial bird.

So Drymon and his team launched a project to study the sharks' diets. Over two years the team caught 50 tiger sharks—mostly within 5 to 10 miles (8 to 16 kilometers) offshore—and dissected their stomachs.

In about half of the sharks, Drymon found "feathers, or beaks, or bird feet, or some kind of bird part."

All the parts were later found to originate from land birds such as woodpeckers, tanagers, and meadowlarks. (See songbird pictures.)

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TAGGED: EARTH SCIENCES