Get a squirrel sized live trap such as the Hav-a-hart live traps. Bait with birdseed at the bottom of your bird feeder posts. When the squirrels get caught (and they will) put a .22 in their head and after a bit of gutting and skinning send'em to your freezer. Repeat till you have enough squirrels to have a small feast then invite the neighbors or at least till you no longer have squirrels raiding your bird feeder.
This worked well for me when I lived in the city. It would work for my father-in-law if he didn't idiotically drive a few blocks down the road to the neighborhood park and release them to return to his bird feeder instead of killing them.
This is who we are, what we do.