Follow this advice to squirrel-proof your bird feeders.
I put my bird feeder 4 feet from the ground, only to watch the “furries” shinny up the pole to eat the seeds. Greasing the pole helped for about 10 minutes, and they figured out the squirrel collar on the pole just as quickly. Finally, I simply put a piece of smooth plastic drain pipe over the feeder pole. Immediate success: The squirrels are gleaners now.