Most tame birds need grit to aid healthy digestion. A bird?s stomach is made up of two parts: a glandular stomach where whole grains are pre-digested with enzymes and a muscular stomach or gizzard where the pre-digested food is ground up. The tiny stones which your bird swallows act like mill stones and turn the food into fine, digestible particles. Grit is a vital part of your pet?s diet. Birds do not have teeth so they need grit to help digest their food.