I just started offering free-choice calcium. My pullets are 20 weeks old and 5 or six of them now have very red faces, combs and waddles. Some are starting to submit to the cockerels instead of running in terror. So I thought it was time to offer calcium; if their behaviour and characteristics are any indication the eggs should not be too far away. I have grit free choice in the run and last night for the first time I put out oyster shells as well. My set-up is a large, portable chicken tractor with a run underneath and an attached portable run that rotates to fresh pasture every day. To encourage them to forage, I withhold feed for the first hour or so that they are in the run. This morning I let them into the run as usual. After morning chores, I went back to put their feed out and noticed that they appeared to have really put a dent in the oyster shells. I thought I read somewhere that too much calcium is really bad for their systems. Do you think that they seemed to eat a lot of shells because they mistook it for "feed" or will they really just self-regulate, and those eating a lot of it were deficient, and I don't need to worry about them "overdosing" on calcium? Thanks, I know it seems like I'm worring over a little thing, but better safe than sorry.