I thought i had some egg eaters within my flock, so i took the egg out last night so they wouldn't eat it. i forgot it by the side of the house, and when i went to let them out, it was opened and licked clean. it looked exactly how the eggs inside the coop did. the coop is predator proof. only thing that might be able to get in there is a snake, but i'd think they'd swallow the egg whole. whatever is getting in there doesn't hurt the ducks. what could it be?