I guess they're thinking they might climb inside and not be able to get out. Chicks do have a way of doing things we may not think of, I suppose it could happen. I leave my chicks for 12 hrs with the chick feeders, without any problems of fouling in it. They won't fly on top of the feeder until a couple weeks, then it would be more of a concern. I also put everything up on a platform, to keep the shavings out. Fermented feed, Starter/Grower and water in the picture. I also provide chick grit after 2 weeks.
