Brutus(the cat) and the Bird

Brutus the cat seems to have developed this strange relationship with this Mockingbird. This has been going on for weeks. Brutus is a part time house cat who was born in the wild under a neighbor's shed. He was captured by my wife and nuetered and loves living in the house most of the time. Recently this has turned into quite the hilarious show everyday. The Bird waits out in the back yard yelling untill Brutus is let out in the morning after eating his breakfast. The Bird sits on our fence or umbrella stand untill Brutus appears and then it starts. Brutus doesn't seem to mind as much as he used to, but he will chase the bird on occasion as it dives toward him. There are other cats in the neighborhood but this bird chases just Brutus. This morning I noticed another Mockingbird came and started to get involved when the original bird continually went after the newcomer and chased him away and then went back to swooping down on Brutus.