Breeding season: April–July, 1 brood per season. - Nest: a large mound-shaped nest of reeds and vegetation right by the water. The same nest is used year after year. - Eggs: 4–6 greenish-white, large (115×73 mm). Incubation 35–40 days by both parents. - Young (cygnets): nidifugous — leave the nest within a day. Moult grey plumage, cared for by the parents for 3–4 months. - The family stays together throughout the winter and travels together to the breeding site the following spring.