We have a little kitty who has been visiting for the past few months and it drives one of my boys crazy. He seems to have some kind of 6th sense that tells him when this cat is in the vicinity as he jumps up on the windowsill and gets really agitated when the visitor is around.
My cat is 99% indoor and the visitor comes and sits on the windowsill and they will hiss at each other and try to hit each other through the glass. My boy gets so upset that he falls off the windowsill in his excitement. As soon as I go and open the back door the visitor runs away.
When he has been outside they have squared up and lots of hissing and screaming at each other. Thankfully the visitor backs down and runs away as my boy has previously got into bad fights with other cats and got hurt and no doubt injured the other cat as well.
Is there any way I can deter this kitty from coming into the garden, and especially onto my windowsills?