text: my daughter wants to know "how does a bird sing?"?   how old is she? i'll try to keep it simple. :-)  birds don't have vocal chords like humans do.  the air they breathe goes through the trachea and the paired bronchi to the lungs. the trachea and bronchi are tubes supported by cartilaginous rings. at some point along the length of the trachea (usually at the place where it splits to form the bronchi), the walls of the tube are enlarged and modified, forming the syrinx (plural syringes). it is formed by modified cartilaginous rings associated with special muscles, and also two membranes at the base of each bronchus. although the exact mechanism for sound production is controversial, it seems that these syringeal membranes vibrate, and the different sounds are produced by modulation of the vibrations by differential contraction of the special muscles. it's been also suggested that the vibrations are not produced in the membranes but in other parts of the syrinx.  in any case, the birds with greater number of syringeal muscles are the best singers. for instance, songbirds have 5-9 pairs of muscles, whereas parrots have 3 pairs; some birds such as storks, ostriches or vultures lack these muscles.