Crows, often praised for their high intelligence, are being put to work as trash collectors in a theme park in France.

Nicolas de Villiers, head of the Puy du Fou historical theme park in the western Vendée region, told the AFP news agency that a team of six rooks—members of the Corvid family—had been taught how to pick up small bits of trash and cigarette ends and put them in a small box. Each time they deposit a piece of trash, the box delivers them a tasty treat.

“The goal is not just to clear up, because the visitors are generally careful to keep things clean,” Villiers told AFP, noting that the birds also “like to communicate with humans and establish a relationship through play.”

Research frequently throws up new discoveries of just how smart these birds can be. A study from Cambridge University and the University of Auckland found that New Caledonian crows can design basic tools (liked hooked sticks and barbed ones made out of plant leaves) from memory, just like humans. The researchers said that “mental template matching” allows crow culture to pass on tool-making traditions.

They can also be mean: Scientists recently discovered that crows gang up on ravens—another member of the crow family—and bully them. Of the nearly 2,000 reported sightings of fights, crows were the instigators 98% of the time. About 70% of the time, they went after ravens in groups.