A guy at the Wild Birds Unlimited in Fort Worth told me my nyjer feeder was basically a squirrel buffet
He said the perch ring sits too low so squirrels just hang off it and clean the whole thing out in one morning, so I finally hung it 8 feet up on a thin pole with a baffle and went from filling it 3 times a week to maybe once every 10 days, though now I'm wondering if the finches actually prefer it that high or if I just got lucky with the placement.