At a historical theme park in France, birds aren't being chased away — they're being trained to pick up litter.

"They do a great job, you know, a very thorough job," the Puy du Fou park president Nicolas de Villiers told As It Happens guest host Matt Galloway.

Six rooks — which are a part of the crow family — have been trained to pick up cigarette butts and other waste at the theme park in the western Vendée region of France.

A falconer at the park taught the birds to collect the debris, and then drop it into a small box.

"As soon as they bring a piece of paper, they get a piece of food, so they understand that it's a kind of game," de Villiers said.

Christophe Gaborit, in charge of the falconry at Le Puy du Fou theme park crouches past two of his crows. Nicolas de Villiers, the president of Puy du Fou Parc, said the trained crows are more a lesson for humans about the downfall of littering. (Sebastien Salom Gomis/AFP/Getty Images)

The falconer started out by placing a piece of paper on the ground nearby, and as soon as the crow picked up the piece of paper and returned it to the trainer, they were rewarded. The distance was slowly increased so the bird had to travel further and further for the piece of food.

The box that the falconer uses has two holes, one for trash and one for the reward, and the birds have figured this out.

Crows, de Villiers said, are known to pick up objects which are "unnatural in the environment" and bring them back to their nests.

"When we [watched] that we just thought, "Oh it's possible, maybe, to organize a game with them."

A lesson for humans

The park calls itself the second most popular theme park in France, bringing in roughly two million visitors each year.

It is known for its historical shows about Vikings, sword fights and a falconry show where crows have been trained to pick up flowers and deliver them to princesses.

Birds perform during a show at French historical theme park the Puy du Fou. (Sebastien Salom Gomis/AFP/Getty Images)

With that amount of park goers, litter is inevitable. But de Villiers notes that the six feathered cleaners aren't replacing the human team.

The birds are instead being used to teach visitors a lesson about littering — and put on a bit of a show.

"The idea is more to educate the human beings to show them that, if you leave the paper in the nature, then you will see the birds cleaning the nature," de Villiers explained.

In their genes

The crow family — which includes crows, ravens and rooks — is famously intelligent. The BBC reports that crows have been observed exchanging gifts for food from humans, as well as using a "crow vending machine" to solve complex problems.

A crow picks up a cigarette end on the parking of the Puy du Fou. (Sebastien Salom Gomis/AFP/Getty Images)

The birds now work at the park four days a week, and de Villiers said that they abide by strict French labour laws. As long as the birds continue to pick up trash, they'll get paid in food.

"They respect the rules, so we respect the rule," he said.

Written by Sarah Jackson. Produced by Sarah Cooper.