Field mice are herbivores that prefer to eat any vegetables, seeds or fruits that are in season. If their preferred foods are not available, they may also eat tree bark, roots or, if they live near a farm, whatever crops the farmer happens to be growing.
Field mice are scavengers and are not picky about their food. If they get hungry enough, they will eat just about anything humans will eat and more. If they take up residence in a house, they may be found eating everything from cat and dog food to kitchen scraps from the garbage. Some mice, if they get hungry enough, have been known to eat their own tails.