My chickens are quarantined into the back of my yard by a four foot tall fence. The last two afternoons, I have found an egg in the middle of the yard that they don't have access to. There is a hole (the size of a quarter) on the side of the egg with little chipped pieces on the ground. But, none of the yolk or egg white has been eaten. What the heck!?! What animal is doing this? A squirrel maybe? Help!