I have 3 Buff O's and the one Barred Rock....One of the 4 has had a color change in her egg shell, I think it is the BR since her eggs have always been a lighter brown than the BO's. But for about 2 weeks now her eggs have become much lighter, not quite white but getting very close, additionally the small end of the egg shell has a little extra shell deposit on it...I think maybe she is trying to copyright her eggs.
wayne

wayne