French theme park uses crows to pick up litter

In my high level lessons this week my students and I studied in English how a theme park in France has established a novel and environmentally-friendly way of keeping its grounds free of litter. It has selected and trained six "intelligent" rooks to pick up rubbish and keep the park clean. Rooks are members of the crow family and are up to 47cm in length. The clever birds will be put to work at the Puy du Fou theme park in the west of France. They have been trained to pick up cigarette ends, paper and other things people throw on the ground.