frighten away other types of birds mark the bird's territory against the same type of bird attract insects wake up other animals
I gave my students this multiple choice question: When a bird sings, it is most likely singing in order to

Only one answer is correct among these 4 choices:
- frighten away other types of birds
- mark the bird's territory against the same type of bird
- attract insects
- wake up other animals

Could you tell me which one is correct?

mark the bird's territory against the same type of bird