Every fall, birders along North America’s Gulf Coast eagerly anticipate the arrival of a variety of songbirds. They’re not the only ones. A new study reveals baby tiger sharks regularly snack on the seasonal fliers, munching birds that fall into the sea dead or alive.
The study traces back to 2010 when researchers identified a wad of slimy feathers barfed up by a baby tiger shark (Galeocerdo cuvier) captured off the Gulf of Mexico. The sharks have been found with everything from chicken coops to unexploded ordnance in their stomachs, and the team expected the feathers to come from a seabird. Instead, they belonged to a songbird.
To find out whether this phenomenon was more widespread, the team surveyed the stomach contents of baby tiger sharks from 2010 to 2018. The team caught the sharks with a rod and reel and then stuck plastic tubes down their throats before releasing the animals back to the ocean.
Forty-one of the 105 tiger sharks the researchers examined had bird feathers in their stomachs. The least digested feathers could be identified by local ornithologists, but some were so far gone they required DNA analysis. The scientists identified wrens, sparrows, and even doves in the gullets of all 41 sharks, totaling 11 different species, none of which were marine, they report today in Ecology.
Researchers think the migrating birds find their way into the sharks’ mouths when fall storms knock them into the sea where—unable to take off again—they drown and become a feathered buffet.