Our broodies will occasionally eat a "suspect" egg and, the following morning, will squirt out a yellowish white liquid that, on the sand of the run, looks like some modern art masterpiece. More often the broodies break a "bad" egg just enough to carry it away from the nest (to a distance of 20-30yds). How they identify a "bad' egg? By a process not well understood Slate hen caught dropping bad egg far from nest (seem almost depressed about it - reason I caught the shot was that she seemed to be "slouching" as she walked around house and I first thought "injury"/"predator"). Royal jenny taking a malformed egg, away from nest:My turkeys have never eaten their own eggs, not once, until I crack them for them, so this is what I do, I also do it with my duck eggs and dirty chicken eggs, not saying you should do it, but this is my experience, and I don't have trouble with it, of course my birds are allowed to forage and do natural things, so they aren't bored or have a need to develop habits that are from improper confinement. It's not natural for birds to crack open and eat their own egg, but if one gets cracked it's fair game