How to discourage cowbirds from hogging my feeder? (1 Viewer)

I run a relatively small feeding operation, just a tall pole with two tube feeders on it and some suet sometimes. But lately, this huge flock of cowbirds has been swooping in at all hours of the day and absolutely DECIMATING my seed supply. I wouldn't mind it so much if it weren't for the fact that they shove out every other kind of bird and all I can do is try and scare them off until they go away! It's really frustrating me. Any tips?

When I had this problem years ago a birder friend suggested I switch to safflower seeds and it seemed to work after a couple of days. Then they moved on.