gold finch

Song - a relatively long, often melodious, series of notes usually associated with some aspect of courtship.

Bird songs are the bird sounds that are melodious to the human ear.

It is bird song which has captured the hearts of human beings.
Birds sing songs as well as give calls. Songs are constructed differently and serve a different purpose to calls. Songs are more musical and complex than calls. They are usually only produced by the male. The male is singing to find a mate and to claim and protect his territory.Where you sing depends on who you are singing to and where you live. Male birds that are trying to attract a mate need to be sure that females can hear their songs as easily as possible.
A bird singing to keep other males out of his territory also needs to be heard. Research also shows that in most birds the presence of a singing male is enough to maintain a territory. The male sings for two reasons then; to proclaim to other males that this is his territory and to attract a mate. Often both these purposes are served by the same song.
Birds put an awful lot of energy into their singing. Singing in some birds at least is as energy expensive as flying. Some birds sing practically non-stop through the breeding season.

It seems that in species with complicated song, the females are turned on by the complexity of the song. Males with more complex songs therefore find mates earlier in the season. The female can benefit as well because the quality of a male's song depends partially on the amount of feed he had the day before, so a male who sings well after a cold night with no food is likely to be good at finding food and therefore worth mating with.

robin

Some musicologists believe that birdsong has had a large influence on the development of music. It is sometimes easy to see some of the specific ways composers have integrated birdsong with music. Certainly birds have influenced some very famous composers: Mozart is thought to have been inspired by the song of a pet starling, and Beethoven's sixth symphony imitates the sound of the nightingale. Bird song is also a popular subject in poetry.