Baby tiger sharks feed on well-known birds such as sparrows and woodpeckers, which scientists have discovered.
Known as “sea garbage cans” the creatures eat almost anything from dolphins to sea turtles to rubber tires. However, before these main predators reach their 15ft adult size they have a much more unusual diet of song birds that live mainly on land.
“Tiger sharks will see an easy meal and catch it, but I was surprised to hear that the sharks ate song birds – I thought they would be seabirds,” says Kevin Feldheim, a researcher in Chicago & # 39 Field Museum and co-author of the study, published in the magazine Ecology.
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Researchers found that these tiger sharks were searching for bird birds struggling to make the huge migration over the Gulf of Mexico. Annually, 2 million birds use this migration corridor to reach spring breeding grounds in North America.
“Tiger sharks shoot on dog birds struggling to fly over the sea,” said Dr Feldheim. ”During migration, they have already worn out, and then they're tired or falling into the sea during a storm.” T
It is likely that terrestrial birds make prey easier than seabirds because they cannot treat themselves as well as on water.
Researchers, led by Marcus Drymon of Mississippi State University, looked at young tiger shark diets through the three-foot wrestling predators of a boat. They then pumped the sharks' stomachs and analyzed a sample of the contents before releasing them, without damaging them.
Out of 105 sharks studied, 41 had bird remains in their stomachs, discovered the researchers.
Since the birds were partially spent, it was difficult for the scientists to say exactly what types of birds they used on their own. However, the residue was sent to a laboratory for DNA analysis.
“None of them were gulls, pollinators, cormorants, or any kind of marine bird. They were all terrestrial birds – the types that could live in your backyard, ”said Dr Drymon.
This is not the first time the tiger sharks have eaten birds.
“There is a site off Hawaii where baby albatrosses learn to fly, and sharks that are our adults are taking them away,” said Dr Feldheim.
However, this is the first time evidence has shown that tiger sharks are eating song birds that live on land. Researchers hope it will help protect them in the future.
“All sharks are in trouble. We don't know the extent to which industrial fishing has been bad, but the vast majority of predator populations have declined in recent years, ”said Dr Feldheim. “It shows us how much more we can still learn about sharks in general and what DNA can tell us that that observation can't,” he said.