Avian Rap: How do birds learn to sing?

Our country has hundreds of varieties of birds, maybe thousands. Does each bird have his own unique song? Does each variety have its own song? No to the first one, yes to the second. But how to they learn their own song?

Here is some interesting info I found online tonight about that question:

SOME birds are just born knowing how to sing the special songs and calls of their own species. In fact, ducklings actually make cheeping noises a few days before they hatch!!
Birds like chickens, turkeys, and pigeons - even when prevented from hearing the calls of their own species - nevertheless develop perfectly normal calls as they grow up.
OTHER birds, such as Canaries and Song Sparrows and those birds we know as "Songbirds", either do not learn to sing their own song or do so only poorly if they are raised where they are not able to hear the singing of their own species.
Baby birds that are raised by "foster" parents may learn to sing the foster parents' song instead of their own.
For instance, Bullfinches raised by a canary grew up to sing a canary-like song.
Baby birds may be more influenced by their own father's song than by the song of other birds even of their own kind.
The offspring of one of the Bullfinches raised by a Canary learned their father's canary-song even though there were other Bullfinches around singing "normally"!
Young birds "practice" until they get it right!
Baby birds while still in the nest make warbling noises known as "sub-song". Only baby birds that learn their song by hearing do this. Song Sparrows begin this warbling at about 13 days of age. Over the next winter, this warbling stops but resumes again the next spring. Finally, by the time the bird is old enough to look for a mate, it will have its song perfected!
By the way, does THIS remind you of anyone YOU know --
Baby birds get their parents to feed them by making "begging calls" - the louder they beg, the harder the parents work in order to satisfy them!
The information on this page came from : (1) Watching Birds, an Introduction to Ornithology by Roger F. Pasquier