This 'bird song' is essentially territorial in that it communicates the identity and whereabouts of an individual to other birds and also signals sexual intentions.
It is not to be confused with bird calls which are used for alarms and contact, and are especially important in birds that feed or migrate in flocks.
Although many songbirds have songs which are pleasant to the human ear, this is not invariably the case. Many members of the crow family make croaks or screeches which sound harsh to humans.
Examples of songbirds include:Common Cuckoo or Little Crake can be contrasted with the variety of a Nightingale or Marsh Warbler.
see also list of birds.