of my sons had the squirrel stealing problem. He is somewhat inventive.
He wrapped two pieces of aluminum foil around the tree trunk about ten feet
off the ground, the pieces of foil were a couple inches apart. He then put
a bare wire under each piece of foil, plugged it into an extension cord that
he plugged into 110 volt receptacle.
He saw a squirrel climb up and when it got onto both pieces of foil, it did
a couple flips off the tree. Didn't kill it.
I certainly don't approve of his method, in fact, I thought it was
dangerous, but it worked - except for the fact that it almost also killed
the tree, I suppose because there was current running through the tree trunk
between the foil wraps.