Max figured out how to pull out the stick that holds the cage door closed, and he lets the budgies out. He twice let some birds out when he was being boarded. The first time the guy didn't know which bird did it, but the second time, when he came into the room Max was sitting nicely in his cage, but several other birds were out. He knew Max was the guilty one because the stick was in his cage (also he saw that he had left the clip off the doors of Max's cage and knew he could easily get out).