I’ve gone through a half dozen squirrel proof bird feeders. None of them offered more than a minor challenge to our resident rodents. Last year I mounted two feeders under the eaves of the house in places too high to reach from the ground, not near anything to jump from, and impossible for even the best squirrel athlete to dangle over the edge of the roof and onto the chain from which the feeder was hung.
It worked. All summer long I watched the alpha squirrel study the situation and try every possible avenue with no luck. He, or maybe she, would stand erect, front paws raised and walk around looking and measuring. All he and the others could do was wait for messy sparrows to toss seeds all over the place. It didn’t take long. They were well fed by default. There were numerous assaults during the winter from the snow covered barbecue, backs of patio chairs, and the tops of various posts. None worked. A few weeks ago he, or maybe she, figured it out. We haven’t seen exactly how it’s done. The only thing we know is that that squirrel can get on top of the feeders as long as he/she is reasonably certain that the dogs are both in the house and not watching.
You have to admire that kind of perseverance.