Swans, with their graceful presence on waterways, captivate observers with their elegance and complex social behaviors. These large waterfowl, often associated with serene lakes and ponds, undergo a distinct reproductive cycle each year. Understanding the stages of this cycle, from courtship to raising their young, offers insight into the natural rhythm of these birds and the dedicated care they provide. Their breeding activities are finely tuned to environmental conditions, ensuring the best chances for their lineage to thrive.
Mating and Nest Building
The breeding season for swans begins in early spring, around March or April. Swans are largely monogamous, often forming lifelong pair bonds, though a surviving mate will seek a new partner if one dies. Courtship rituals involve synchronized movements, such as head bobbing and quivering wings, as the pair strengthens their bond.
Once paired, swans select a secluded nesting site near water, offering protection from predators and flooding. These sites are situated on slightly elevated ground, small islands, or floating vegetation mats, providing a secure foundation. The male (cob) gathers materials like reeds, sticks, and aquatic vegetation, bringing them to the female (pen) who then arranges them to form a large, circular mound. This structure can be substantial, with mute swan nests reaching up to 3.5 meters in diameter and 0.6 meters in height. Nest building can take several weeks, beginning in mid-April.
Eggs and Incubation
After the nest is complete, the female swan begins laying her eggs, typically from late April to June. She lays one egg every one to two days until the clutch is complete. A typical clutch consists of 5 to 10 creamy white eggs. Mute swan eggs weigh around 340 grams.
The female starts incubating the eggs only after the last egg has been laid. This synchronized incubation ensures all cygnets hatch around the same time, allowing uniform parental care. The incubation period lasts 32 to 45 days. During this time, the female does most of the incubation, rarely leaving the nest except for brief periods to feed and preen, while the male remains nearby to guard the nest. She develops a brood patch, a bare area on her underside, which allows for direct heat transfer to the eggs.
Raising Young Cygnets
The hatching of cygnets occurs from May through July, 35 to 42 days after incubation begins. All eggs within a clutch hatch within a 24-hour period. Newly hatched cygnets are covered in fluffy grey down and can leave the nest within a day or two, quickly learning to swim and dive.
Both parent swans (cob and pen) share responsibilities in raising their young. They guide cygnets to foraging areas, pulling up aquatic plants and stirring up sediment to help them find food, and also feed them small invertebrates. For the first few weeks, cygnets ride on their mother’s back for warmth, protection, and transportation. The parents remain protective, defending their young from threats.
Cygnets stay with their parents for four to ten months, sometimes until the next breeding season, learning essential survival skills like foraging and avoiding predators. They develop quickly, reaching about half their adult size and gaining their juvenile grey plumage by 8 to 10 weeks of age. By 13 to 17 weeks, they begin to learn to fly, though they may not be fully independent until the following spring when their parents encourage them to disperse.