Most tame birds need grit to aid healthy digestion a birds 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 pets diet birds do not have teeth so they need grit to help digest their food