A songbird is a bird belonging to the clade Passeri of the perching birds (Passeriformes)This group contains 5000 or so species found all over the world, in which the vocal organ typically is developed in such a way as to produce a diverse and elaborate bird songThe song in this clade is essentially territorial, because it communicates the identity and whereabouts of an individual to other birds, and also signals sexual intentions. Sexual selection among songbirds is highly based on mimetic vocalization. Female preference has shown in some populations to be based on the extent of a male's song repertoire. The larger a male's repertoire, the more females a male individual attracts. It is not to be confused with bird calls that are used for alarms and contact and are especially important in birds that feed or migrate in flocks. While almost all living birds give calls of some sort, well-developed songs are only given by a few lineages outside the songbirds.