My sister has 2 mockingbird that each have a "cat" to chase. One lives in a tree and chases the Momma cat and the other one lives in a shed and it chases the other cat....if one chases the "wrong" cat, the other mockingbird will chase the other mockingbird away. Reminds me of "he is my brother and I can hit him, but you can't hit him because he's my brother", lol!