Is it true that birds have teeth in their stomachs? why?

We can say that this statement is true! Teeth are needed for grinding food, so that later it is better digested in the stomach. The body of a bird has no teeth, but it has a very strong acid and enzymes for digestion, and birds also swallow small stones for mechanical grinding of food. Thus, the food, getting into the stomach of the bird in an unmilled form, is easily broken down there.