 Generally, black swans in the Southern hemisphere nest in the wetter winter months (February to September), occasionally in large colonies.A black swan nest is essentially a large heap or mound of reeds, grasses and weeds between 1 and 1.5 metres (3–4½ feet) in diameter and up to 1 metre high, in shallow water or on islands.A nest is reused every year, restored or rebuilt as needed.