Songbird

Songbirds are the main group of birds in the order Passeriformes. They are the suborder Passeri, sometimes called 'oscines' (Latin for songbird). They are a genuine clade.
There are about 4000 species of songbird. Their "syrinx" (vocal organ) is able to produce varied and beautiful singing. They are a "very" successful group of birds, in fact they are the dominant birds on Earth today.
It seems songbirds evolved 50 million years ago in the part of Gondwana which later became Australia, New Zealand, New Guinea and Antarctica. They then spread around the world.
Song.
Their song is mainly territorial: it communicates the identity and whereabouts of an individual to other birds of the same species. It also signals sexual intentions. Female preference in some populations is based on the extent of a male's song repertoire. The larger a male's repertoire, the more females a male individual attracts. 
Bird calls are also used for alarms and contact. They are especially important in birds that feed or migrate in flocks. Although almost all birds give calls of some sort, well-developed songs are only given by a few lines outside the songbirds.
Families.
Corvida.
This is now known to be a paraphyletic group and so it is not used in modern systematics.
Passerida.
This is accepted as a clade.