We all love to hear the birds sing. It gives us a very pleasant feeling, especially when we visit forests or travel to the countryside. Some birds produce very sweet sounds, while others produce harsh and unpleasant sounds. Do you know why birds sing? The songs and calls are means of communication among birds. They sing to attract mates in the mating season, to warn other birds of any impending danger from predators, and to establish their home territories or nesting area. The birdcalls are usually distinctive and vary from species to species. This distinction helps the birds to identify the calls. In all species of singing birds, the male is usually the singer. It sings to attract the female bird. The nightingale produces the best musical effects, which no other bird can match. The mockingbird has its own harsh call, but can imitate the songs of other birds. The crow makes a very harsh cawing sound. You wouldn’t call a crow’s cawing musical, would you? Apart from singing, birds make other types of calls — calls for sending alarm signals, for food or calling their parents, calls made in an aggressive or hostile mood, etc. A few birds, such as pelicans and cormorants, are voiceless. The singing birds belong to the suborder, oscines. Their vocal cords are located in a special box, called the syrinx, located at the base of the windpipe where it divides into two bronchi. The syrinx has a bony structure and forms a sound box within which membranes vibrate when the bird exhales. This produces varying notes in the bird’s sound. The structure of the syrinx varies from species to species, of which seven different types have been identified. Birdsong has a pitch of about 4300 Hertz, which is even higher than the highest note of a piano. Intensity of the call of any single bird varies from the deep-pitched hoot of owls to the very high frequency chirping notes of small birds, which are barely audible to the human ear.