Polly want a finger

There's a large supermarket-style pet shop near here that for a long time has had a popular resident talking cockatoo that customers have always been able to touch. I've done so many times, but not any more. Yesterday he bit my mouse finger - YOW!!! - and instantly there was lots of bloodflow. Boy, they sure bite hard. At my suggestion, the shop assistant said she would put a warning sign on the cage.