Crippled or sickly birds may invite attacks which turn into cannibalism. Cannibalism may begin from birds being allowed to devour a bird which has died and not been disposed of by the poultryman. Bloody wounds may be picked at by other birds and may be the start of the problem. Provide quarters which are warm enough to keep combs and wattles from freezing. Keep roosts clean and litter dry.
Birds learn the trick from each other.
Several different causes may get egg eating started, most of them related to the accidental breakage of eggs. Remove eggs promptly that have been rayed on the floor.