hmmmm ... some of us have chickens that apparently haven't read that part of the "Chicken Operator's Manual". Lots of folks (myself included) feed chickens crushed egg shells - with nary a pecked egg in sight. whole shells, on the other hand, might seem to be a little too much like encouraging cannibalism.Hard boiled eggs do not encourage them to eat their own eggs. It is good protein for them. Feeding them crushed egg SHELLS (instead of oyster shell) can encourage them to eat their own eggs.
We crush up egg shells as they're used, and toss 'em in with the rest of the compost, which the chickens scratch about in daily. Seems to me like a great way to recycle those minerals and nutrients - in the chicken, and in the compost.