Squirrels are pretty clever. There was a program a few years ago on UK tv where they made a sort of obstacle course for one to get to its food. They kept making it more complicated and each time, the squirrel worked out how to solve the new part of the puzzle.
I think we have about 8 bird feeders and a couple of tables here. Any creature that can get to the food is welcome to it. The food is cheap enough... Reminds me though we need to get another sack of seed. We get a 25kg sack these days - it lasts ages.
I am annoyed with one rodent at the moment BTW. I'd taken all the seeds off our sunflowers and left them drying out. A rat has got into the shed and eaten the lot.
Jon
PS. Another thought... Ground feeding of squirels and birds is out of the question here. We have 4 lively cats and our feeders have to be placed where the cats can't get to.