阅读对话，回答下列问题。

Peter: Wow! So many animals! How many ducks do you have?

Grandpa: I have twenty.

Peter: Oh, a big pig! How many pigs do you have?

Grandpa: Four. One mother pig and its three baby（婴儿）pigs.

Peter: They are really cute. Look! I see some chickens（小鸡）.

Grandpa: How many chickens do you see?

Peter: One, two, three. . . I see twelve!

Grandpa: No! The black one is a bird.

Peter: Oh, I see. I like this farm（农场）.