To answer the original question about how to feed the chickens egg shells, this is what I do. Wash out the shells as you use them so they don't start smelling awful. I collect mine in the large cup of my Magic Bullet blender. After the cup is fullish I add a cup of water and blend away. Only takes seconds. Will be super fine. That's good. Now, take a plastic dish tub or something about that size. Put some water in it. Add a little diatomaceous earth, food grade, to the water. Also the egg shells, some unfiltered apple cider vinegar and some oregano oil. Stir this mixture completely then add enough dry chicken feed to completely soak up the concoction and stir it some more so that the ingredients are evenly mixed in. I don't do this every day of course. It is just a very easy way to get all 4 ingredients down them occasionally. Also they love wet food.
So the other day, I arrive home, get out of the car, come walking up towards the house, and all the chickens and ducks come running to me and all start talking to me like crazy. The human rooster says, "They don't talk to me like that!" So I told him the truth. "You don't feed them any treats like I do." I hope one of you appreciates what I found to be humorous.