Black Swan couples build large nests from branches and reeds, either floating on the water or on the ground. Both males and females incubate the eggs. Young swans can fly at about 5 or 6 months but stay with their parents until the following spring. Cygnets have a light-grey plumage that turns black by the time they are a year old.
 
To defend their territory, males assume an intimidating stance, spreading their wings, bending their neck into an S shape and puffing up their feathers while pretending to charge their enemy.