People usually sing because they like music or because they feel happy. They express their (26)__________ by singing. When a bird sings, (27)__________, its song usually means much more than that the bird is happy. Birds have many (28)__________ for singing. They sing to give information. Their songs are their language. The most beautiful songs are (29)__________ by male (cock) birds. They sing when they want to attract a female (hen) bird. It is their way of saying that they are looking for a wife. Birds also sing to tell (30)__________ birds to keep away. To a bird, his tree or even a branch of a tree is his home. He does not want strangers to come near him, so he sings to warn them.