Book 31, Question 2
Why do some birds swallow small stones?
Birds have no teeth, so they cannot chew.
Instead, many birds swallow tiny stones called grit, which collect in a strong, muscular stomach part called the gizzard. When the gizzard squeezes, the stones rub against seeds and tough food and grind it to mush. Without grit, a seed-eating bird would struggle to get energy out of its meal.