Today's species is another familiar one: the mute swan or Cygnus olor. It is the commonest swan in the UK and named because compared to the other swans (whooper and bewicks) it isn't as 'vocal'. The black swan of Australia is it's closest relative, phylogenetically speaking.
The monarch 'owns' all 'unmarked' swans, though this right was extended to the Dyers' and Vintners' Companies in the fifteenth century.
The knob at the top of the bill swells during the breeding season on males only, helping to tell them apart. The males are called cobs. They generally pair off and stick together for life, consequently they are a symbol of fidelity. The most famous mute swan is the 'ugly duckling' in the story by Hans Christian Andersen.