I heard Oyster shells. I've found 2 eggs in the last month that the top was missing and the majority of shell had been removed from the membrane and of course empty. I had a feeling it was one of the silkies that I got from my sister. Well the other day I actually caught her standing there pecking the egg. It had been moved to the same spot the last one I found was (not where they choose to lay) and I am pretty sure it's her. I don't have a problem getting rid of her if I need to, but I thought if there was a suitable way to stop it I would give that a try first. When I took them I noticed some irregularities in the shell quality of hers versus mine, and I wondered if they had been lacking something in their diet that might be making her do that.
Thanks. I'll have to get some this week and try it.
Good luck! I have a small feeder of oyster shells in my run, because I don't really know how old my silkies are, but I think they are getting close to 20 weeks. The comets will peck at it some, but I do see the silkies eating it more than all the others. So either they know that they need it, or they just like the taste better than the others! lol