I made a bird feeder atop a metal pole. To prevent squirrels gaining access, I made a funnel shape out of alloy, about 18" diameter at the wide end, hole in the narrow end to suit the pole. Fitted to pole, so it just sits on a clamp, on the pole. The funnel, is free to rock and move. The squirrels have nothing to grip, to get past the funnel, we have never seen them even try.

