At least one poster has had a roo starve to death, or come very close to that when using a PVC feeder.
I think the instance @lazy gardener is referring to is that the bird could not get it's head (with large comb) into the opening to get feed. It was one of the type like RonP shows above.ETA: Is it the sharp edges that causes the problem? Or is it more a matter of simple repetitive moving contact with the edges as they fit their heads down inside?