True story - when I lived in Seattle, I had a bird feeder hanging from a tree branch just outside my office window. But birds seldom used it, because squirrels kept raiding it. After a while, I decided that the squirrels were far more interesting than the birds, but I had to make it a challenge for them (and fun for me).
First I added one of the plastic semi-circular baffles to the feeder, which prevented the squirrels from climbing down from above. The squirrels learned to jump up from below the feeder using objects in my yard, so I moved the bird feeder a little higher, and then I watched with great amusement as the squirrels would continue to jump from the ground, but miss by a good distance. Then they would climb back up on the objects in my yard, and just stare at the feeder - as if to say, "Huh. That worked yesterday."
Then they learned that they could jump from the trunk of the tree and grab on with just one claw before crashing to the ground, but that was enough, and they resumed their raids. So I moved the feeder a little further out on the branch, and watched with great amusement as the squirrels would now fall far too short and hit the wall of my house with a dull thud. People would come in the office to talk to me and hear, "Clunk. ... Clunk. ... Clunk." They'd look at me quizzically, and I'd say, "Meh. It's just my squirrels."
After a while the squirrels learned that it wasn't going to work, so they'd climb the tree and just stare at the feeder, and I could tell that they were weighing every option available to them. Mind you, I kept refilling the feeder with store-bought squirrel food this entire time. Even though I was making life difficult for them, I was still trying to keep them well fed.
Eventually I noticed that the birds had returned, but by then I could not have cared less about them. Seeing birds on my feeder meant that my squirrels had been defeated, and my heart went out to them. After all, the squirrels had worked so hard for so long.
I decided to cut the squirrels a break, and I moved my feeder so that it was back in long distance jumping range for them. I never saw the birds again, but that didn't bother me at all - because almost every day from then on I saw a squirrel hanging on the feeder upside down by one claw. We'd make eye contact for a moment, and I knew they were grateful. Or annoyed. One can never be too sure with a squirrel.