Only the Rollerfeeder is still out there

Currently there are six different feeders in my garage that all claimed to be squirrel proof. Obviously these squirrels must benefit from living only a few miles from Harvard University, since they’ve outwitted every one of them–and I have pictures of them in the act to prove it. Only the Rollerfeeder is still out there, guaranteeing the birds access to food without competition or finding an empty tray. John, Essex Massachusetts (Owner of 2, recently purchased 3rd Rf)