I think ours is. It is a gallon glass jar which sits in a kind of holder that allows them to go in the side and turn into the jar.
We noticed our corn vanishing, cob and all. Then we saw one if the 'babies' dragging an ear out of the feeder and 20 or 30 feet across the deck. Jumped into the tree and off to who knows where. It is s stitch. When I was young, we didn't treat them so kindly.