are Gulf oil and gas rigs to blame?Feathers of woodland birds found in tiger shark bellies this fall bolster the theory that the Gulf’s offshore oil and gas platforms pose a fatal danger to migrating birds, according to scientists from the Dauphin Island Sea Lab.
“The best way I can describe what we found in the sharks is to think of a hairball like cats cough up,” said Marcus Drymon, a Sea Lab scientist who dissected several of the sharks. “The balls are just solid feathers and about as big around as a grapefruit. We caught these sharks during the fall migration in the general vicinity of the platforms off Alabama.”
Feathers in the mouth of a tiger shark caught south of Dauphin Island belonged to a yellow-bellied sapsucker, a woodpecker that migrates across the Gulf of Mexico each year, Drymon said. The red feathers in another shark’s belly came from a scarlet tanager, and the brown ones belonged to a brown thrasher. Drymon and his fellow scientists said they have found feathers in years past during an ongoing shark survey but didn’t make the connection to migratory birds until they read a November Press-Register article.
It described a 2005 federal study documenting a phenomenon called “nocturnal circulation,” during which birds migrating across the sea on cloudy nights became disoriented by the brightly lit oil platforms. The birds flew around a platform for hours, often until they died of exhaustion and fell into the water.
In some instances, scientists estimated that flocks of 100,000 or more birds were circling a single platform.
The study concluded that more platforms in the waters south of Alabama would “not be benign to migrating birds” as the area lies at the center of the Dauphin Island Trans-Migration Throughway — one of the largest migratory bird corridors in North America.
All manner of birds — including hummingbirds, warblers, herons, cuckoos, doves, egrets, falcons, orioles, sandpipers and osprey — cross the Gulf twice each year and have been documented circling platforms.
Though the 2005 study urged follow-up research, federal officials said they have not conducted any.
“While there are no bird studies under contract in the Gulf at this time, we do anticipate seeing more bird studies funded in the Gulf of Mexico in the near future,” the Bureau of Ocean Energy Management, Regulation and Enforcement’s Eileen Angelico wrote in response to the Press Register’s story in November.
Angelico said the agency could not comment on the Sea Lab research because the findings had not been published or reviewed by federal scientists.
“A lot of what we think is based on the Press-Register article that suggested the platforms could be the culprit,” Drymon said. “These are not gulls or pelicans. They are migratory birds that you would not typically find in a shark.”
Drymon said tiger sharks are the most likely candidate for eating birds that fall into the sea, as they are famous scavengers. “These are birds that aren’t supposed to be on the surface. They can’t swim, and their feathers can’t get saltwater on them,” said the Sea Lab’s Sean Powers, who is part of the shark survey team. “If these birds end up on the water, they are going to die.”
Powers said it wouldn’t be unusual to find a few migrating birds in sharks off Alabama in the spring because “they would be in the last 20 miles of an 800-mile journey” and might have lacked the energy to complete the trip.
“But in the fall, birds falling into the water in the first 20 miles, those birds wouldn’t have taken off if they hadn’t been able to make it all the way,” Powers said. “These birds died in the first 20 miles. It suggests something interfered with their migration, and it really suggests a link to the platforms.”
Drymon said the scientists planned to publish their findings and seek research money. He said DNA testing on the feathers in the sharks’ stomachs could help identify more species being eaten.
In addition, a relatively new technique that relies on weather radar to track bird migrations could pinpoint platforms where flocks of birds ended up circling.
This migratory bird's body was found in the belly of a tiger shark caught in the Gulf of Mexico. Scientists said the discovery of feathers from various migratory birds in sharks caught during the fall migration suggests that oil and gas platforms in the Gulf present a fatal danger
