Native to South America, the black-necked swan breeds in the far south and migrates to the centre for winter.

The male (above left) is larger than the female and has a darker red "caruncle" on his bill.

Head of male (above left) and female (above right) both have a fleshy "caruncle" on the beak (a salt-extracting gland which also indicates maturity)

The immature swan doesn't yet have the full red knob on the beak

Black-necked swans with two cygnets. Both male and female are dutiful parents and both will carry the young on their backs.

Older cygnets: dark neck and head beginning to emerge; body turns from white to grey and later back to white; bill turns from dark grey to pink and back to dark grey plus red caruncle.