What structure is an adaptation that helps birds break food down?

Birds have a specialized digestive structure called the gizzard, which is a muscular part of the stomach that grinds food. The gizzard works in conjunction with the bird's beak, which helps in initially breaking down food. Some birds also ingest small stones or grit to aid in the grinding process within the gizzard, enhancing their ability to digest tough food items efficiently. This adaptation is crucial for their survival, allowing them to process a variety of diets.