Swans are among the largest and most recognizable aquatic birds globally. As members of the Anatidae family, which includes ducks and geese, they reproduce by laying eggs. This begins a complex annual cycle of nesting and parental care. Developing a new generation requires significant effort from both parents, from establishing a territory to guiding the young through their first year.
The Reproductive Cycle and Nest Location
The breeding season typically begins in late winter or early spring, often around March or April, when the pair becomes intensely territorial. The female (pen) lays the eggs, while the male (cob) plays an active role in preparation. They select a nesting site that provides easy water access and safety from predators, frequently choosing a small island or a heavily vegetated shoreline.
The nest is a substantial structure, built as a large mound of reeds, sticks, and other aquatic vegetation, often measuring a meter or more across. The cob gathers the material and transfers it to the pen, who molds it into a bowl-shaped depression. The pair establishes a nesting territory during this period, which the cob defends fiercely against intruders.
Characteristics of Swan Eggs
After the nest is complete, the pen begins laying her clutch. She usually lays one egg approximately every 24 to 48 hours, resulting in a clutch size that typically ranges from four to eight eggs. Some pairs may lay as many as twelve.
Swan eggs are notably large, reflecting the size of the adult bird, often measuring around 113 millimeters (4.5 inches) long and weighing between 330 and 375 grams. When first laid, the eggs can be a pale greenish-blue or grayish-white color. This color gradually changes to a stained white or chalky appearance from contact with the nest material and the parents’ feet.
Incubation and Shared Parental Duties
The pen does not begin incubation until the entire clutch has been laid. This synchronized start ensures that all embryos develop at the same rate, allowing the entire brood to hatch almost simultaneously. The incubation period generally lasts between 34 and 45 days.
The pen performs the majority of the incubation, remaining on the nest almost continuously. She uses a specialized, featherless area on her abdomen called a brood patch to transfer heat directly to the eggs. While the pen is restricted to the nest, the cob patrols the territory and acts as the guardian, ready to confront threats.
From Egg to Cygnets
The successful completion of incubation culminates in the hatching of the young, which are called cygnets. Swans are classified as precocial birds, meaning the cygnets are relatively mature and covered in fluffy grey or white down when they emerge. They are able to leave the nest and enter the water with their parents within 24 to 48 hours of hatching.
The cygnets’ immediate life is one of dependence and rapid learning. Both the pen and the cob remain co-parents, providing protection, guidance, and warmth. Parents often help the cygnets find food by pulling up submerged aquatic plants, teaching them to forage. The young swans typically remain with their parents through their first winter to learn necessary survival skills before striking out on their own.