The scary stuff that sharks eat; the solutions are for the birds
A new study by the Dauphin Island Sea Lab in Alabama finds that tiger sharks in the Gulf of Mexico are eating a lot more than fish and other marine life. Their diet also includes land-based birds, such as woodpeckers, tanagers, meadowlarks, catbirds, kingbirds and swallows.
The question is how these birds end up in a shark's stomach and the American Bird Conservancy thinks it might have the answer. The conservancy has been tracking studies that show that lights on oil rigs appear to confuse birds during their flights over the gulf, leading them at times to their deaths, and sometimes in large numbers.
According to the conservancy:
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.
The conservancy has what appears to be a rational path to stop this: bird-friendly lighting, which is already in place in the Netherlands. In some cases, changing the color of the lights from the usual white or red, to green (what else?) solves the problem. Other studies indicate that flashing lights rather than steady ones don't cause the visual disorientation.
It seems like a cheap enough solution for U.S. oil rigs to try.
-- Karin Klein
Photo: A sand tiger shark at the Aquarium of the Pacific. Credit: Aquarium of the Pacific