Emily Tripp
Senior Writer

It is not uncommon for sharks to eat sea birds, but lately, researchers have been finding land birds in the stomachs of tiger sharks living in the Gulf of Mexico.

“We’re the first to look this exhaustively at the diet of tiger sharks, as far as I know, and this certainly seems surprising,” said fisheries ecologist Marcus Drymon, leader of an ongoing tiger shark diet study at the Dauphin Island Sea Lab ^[1] in Alabama.  The researchers have found woodpeckers, catbirds, kingbirds and swallows in their stomachs.

The American Bird Conservancy ^[2] suggests that oil platforms are the reason because night-flying birds are known to get trapped in bright light sources.  There are more than6,000 illuminated platforms in the Gulf and they could all be potential lures for these night-flyers.  They become confused by the bright light and often fly in circles until they are too exhausted to continue and they fall into the water, effectively becoming shark food.

“Unfortunately, we don’t have good baseline data to know that,” Drymon said.  “We don’t know if migratory birds are normal things for them to eat or not.  There’s no data on tiger shark diet from 100 or 50 or even 30 years ago.”

Migratory land birds from the US typically fly to South America for the winter in a hundred to a thousand mile journey.  The birds stay on course primarily using their internal compass, but they use the moonlight to aide them.  Light pollution can interfere with their system, but researchers have only just started to study this problem.

To read more about the effect of light on birds, you can read the full report here ^[3].

Copyright © 2012 by Marine Science Today, a publication of OceanLines LLC.