Why do birds sing?

Birdsong serves two central purposes: advertising for a mate and warning rival birds to stay out of a claimed territory. Males often sing the most, especially in the breeding season, and females may judge a potential partner by the complexity and vigour of his song. Birds produce these sounds with the syrinx, a unique organ at the base of the windpipe that can generate two notes at once, giving some species remarkably rich and layered songs. Many songbirds learn their songs by listening to adults during a sensitive period when young, much as human infants learn speech, and regional populations can even develop distinct dialects. The dawn chorus, when birds sing most intensely just before sunrise, occurs because still, cool morning air carries sound farther and there is little else to do before the light is good enough to forage.