Birdsong

• Songbirds utter complex vocalizations that include harmonious whistles, trills, yodels and short cheeping notes.

• Males are the songsters, but females of some species, like cardinals, also sing.

• Birdsong begins as air from the lungs vibrates thin membranes inside the syrinx, or voice box, at the base of the windpipe.

• Muscles in the syrinx tense and relax the membranes to produce melodies and call notes.

• Birds can sing with closed beaks because their songs are shaped inside the syrinx, not inside the oral cavity as with humans.

• Nonsinging birds, like male woodpeckers, utter a nonmusical chatter and attract females by rhythmically drumming their beaks on wooden or metal surfaces.