A songbird was an avian belonging to the suborder of perching birds. This group contained particular species, in which the vocal organ typically was developed in such a way as to produce a diverse and elaborate bird song. This 'bird song' was essentially territorial in that it communicated the identity and whereabouts of an individual to other birds. It was not to be confused with bird calls, which were used for alarms and contact, and are especially important in birds that fed or migrated in flocks. Although many songbirds had songs which were pleasant to the Human ear, many members made croaks or screeches which sound harsh to Humans.