A theme park in France employs six crows to pick up litter (Boubou, Bamboo, Bill, Black, Bricole and Baco)

This week, the Puy du Fou theme park in western France put some new employees in the field: six trained rooks, members of the crow family, picking up small pieces of paper and cigarette butts in exchange for food.

The Puy du Fou trash collection system is similar to Klein's "vending machine," rewarding birds with food for picking up certain items off the ground. It uses two different sections of a wooden box, one to receive trash and the other to offer up food.

"The park is very clean," Puy du Fou President Nicolas de Villiers tells NPR by phone. "The purpose of the crows ... is to educate the people, to open their minds, to think, 'OK, the birds are able to do something that we are much more able to do than them, so we should do this by ourselves.' "

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