The Two-Way
1:39 pm
Thu January 12, 2012

How Do Land Birds End Up In A Tiger Shark's Belly?

Scientists are facing a riddle. For two years, researchers at Dauphin Island Sea Lab in Alabama have been studying the diets of Tiger Sharks in the Gulf of Mexico and they found that the sharks not only eat sea creatures, but also make a habit of eating land birds. Yep that's right woodpeckers, catbirds, kingbirds and swallows have all been found in their bellies.

Naturally, sharks aren't exactly walking onshore for a snack and the researchers at the Sea Lab said bird migration might explain it but fisheries ecologist Marcus Drymon told Wired that they didn't have good baseline data to know if Tiger Sharks have been eating migrating birds for years. Essentially, he was saying they don't know for sure how these sharks are getting their birds.

The American Bird Conservancy, though, put out a theory this week. They believe it might have to do with oil rigs. They say land birds have been known to be attracted to the lights of oil rigs and the attraction can be fatal.

They explain:

"These avian fatal attractions occur more often on cloudy nights, and can involve hundreds or even thousands of birds that apparently confuse the platform lights with stars by which they navigate. The birds become trapped in a cone of light – either reluctant or unable to leave it and fly into a wall of darkness.

"'Some birds circle in confusion before crashing into the platform or falling from the sky, exhausted. Others land on the platform where there is no food or drinking water. Some of these birds continue on quickly, but many stay for hours or even days. When finally able to leave, they can be in a weakened state and unable to make landfall, and ultimately, are more vulnerable to predation,' said Dr. Christine Sheppard, Bird Collisions Campaign Manager for ABC."

That sounds like a reasonable theory. What do you all think?

Copyright 2012 National Public Radio. To see more, visit http://www.npr.org/.