Hello Rob,
Sorry to see the birds are not playing ball, but if you have active cats, the birds will equate them with predators. How much cover within a couple of feet is there for the birds ? I have the same feeders, but instead of sticking them into the ground, one is bound onto a sapling, so same height for the feeders but some young branches to provide perches, one is stuck into a bed of hollyhocks - seed heads left on so there are long stems, and one is inside a domed rose support - we do have a cat, but he wears a bell, and the birds still come to the feeders. A bowl of water and some fat balls might help, especially if we have some very cold weather. Will keep fingers crossed for you.