I understand the OP's distress. I have two cats, one of whom is a terrific hunter. I don't let her out at all, as I am well aware that she would kill anything she can get hold of. My two cats are rescues from Romania, whose early life was on the streets. Obviously, they had to survive however they could - but all wildlife has to kill something else to survive. They can't exactly go to the shops for their food, as we do.
I love birds too, and all other wild creatures big enough for me to see. I can't walk or stand long enough to be able to walk a dog, or I would have one! I'm partially sighted and could not walk outside very far, and still be safe.
My cats are my comfort, just as a dog is to their owners. They are soft to stroke, loving and affectionate and make me smile every day. Just like dogs,they know when you are sad and try to comfort you. MollyPolly60 if you ask around maybe there is a cat rescue in your area that will try to Trap, Neuter and Release feral cats. I know if won't solve your problem, but there would not be more and more feral's then, to cause more problems. These cats don't want to live wild, where they are subject to disease, hunger and attack (sometimes from dogs) - they just don't have any other options.