A routine activity of many bird species is singing. Birds also make sound in their throats just like us. The sound box of the bird is called syrinx which is at the bottom of the windpipe. The voice box in humans called larynx is at the top of the windpipe. Also the length of larynx in human varies between 18-23 mm. Deep voiced birds such as whooping cranes and trumpeter swans have windpipes that measure an amazing three or four feet. Only a few species such as European white stork are voiceless because they have no syrinx.
Most birds sing in the morning, evening or twilight hours. Mocking birds and nightingales are nocturnal songsters. Among all species, males are the impressive songsters. They sing primarily to establish a claim to a territory and some repeat their songs thousands of times a day. Most species stop singing as the breeding season ends.
Birds communicate primarily with call notes, using them to scold, call the young ones, beg for food and help them stay together within a flock. Whether songs or call notes, their sounds are especially significant in forests, where often it is far easier to hear than to see.Bird watchers rely mostly on sound to identify certain kinds of flycatchers, for example they cannot tell the species apart by sight