Proof of Evolution? Birds of Prey Avoid Extinction by Growing Longer Beaks in Just 10 Years

A snail kite seen over Honduras. Orlando Sierra/AFP/Getty Images

In an impressive feat of adaptation, the beak size of a particular bird of prey has changed in just 10 years in order to keep up with a change in its food supply.

In 2005, snail kites, which live in central Florida, got a nasty surprise. The birds get their name from their very favorite food, apple snails. These birds are equipped with a long, hooked beak perfect for snatching the snails out from their spiral shells. But between 2005 and 2008, those apple snails were replaced by a foreign, larger relative. Rather than starve, the snail kites were able to grow larger beaks in order to keep pace with their tasty targets—all in less than a decade, according to a new paper published in the journal Nature Ecology & Evolution.

The University of Florida scientists who are behind the paper say that right now, it's too early to call the phenomenon evolution because the change doesn't appear to be something parent birds pass on to their chicks. But they say that could change as the invasion of larger snails continues to unfold. "Our findings suggest that evolutionary change may be imminent and underscore that even long-lived vertebrates can respond quickly to invasive species," the authors write in the paper.

The invasive snails, known as Pomacea maculata and nicknamed giant apple snails or spotted apple snails, are originally from South America. The handsome snails were brought to the U.S. through the aquarium trade and then released, likely because they chomp through aquarium plants so quickly. Now, they're chomping through the wetlands of Florida and other southeastern states—and they lay thousands of eggs every week, so their population is thriving.

Scientists wanted to know how the birds who feast on snails were doing as the smaller, native snails began to be replaced by the larger invasive snails. In the paper, they show that during the first year, larger birds and birds with larger beaks are surviving more than their smaller and smaller-beaked brethren, leading to an adult population that has picked up the same characteristics.

And that's been a remarkably fast change, with the difference visible in less than a decade, or about a generation and a half in snail kite time.

Read more: Australia Wants to Breed Giant Snails to Save the Great Barrier Reef

The kites still appear to prefer the native snails when they can find them, they've just gained the flexibility to augment the menu with invaders. That could be a huge silver lining to the invasion: Scientists think that the extra food source is giving the birds a way to hang on even as their habitat changes.

In the Everglades the birds are officially considered endangered and protected under the Endangered Species Act—and have been since 1967. Closely related species of snail kites also live in southeastern Mexico, Belize and Guatemala.