Everything you need to know about mute swans

Mute swans are a familiar sight on ponds, lakes, rivers, and other waterways in urban areas. Because they often live close to towns and cities, many people encounter them during everyday walks and exercise near their homes. They are the largest and heaviest waterfowl species in the British Isles and are also the only swan species there that remains year-round rather than migrating. However, they may still travel to different parts of the country during winter when better feeding opportunities are available.

What Does a Mute Swan Look Like?

Adult mute swans have entirely white plumage, although their heads can sometimes become stained a rusty brown color when they spend time feeding in acidic water.

The male is called a cob, while the female is known as a pen. The two sexes look very similar, but the male is generally larger, with a somewhat longer head and body and a broader wingspan. During the breeding season, the black knob at the base of the male's bill becomes swollen and much more prominent than that of the female. Outside the breeding period, however, telling males and females apart can be quite difficult.

Young mute swans have bills without the prominent frontal knob found in adults. Their bills are initially pinkish-grey with black areas, gradually becoming more pink during their first winter. By their second winter, they develop the shape and coloration characteristic of adults.

Cygnets can look quite different from adults when they hatch. Their bodies may be covered in dusky brownish-grey down, while their bills are grey-black.

What Sounds Do Mute Swans Make?

Despite their name, mute swans are not actually silent. They are simply the least vocal of the swan species. They produce a range of short grunts and hissing sounds.

During the breeding season, they can also make brief, powerful snorting noises. Unlike some other swan species, however, they do not produce the familiar honking calls associated with birds in flight. When a mute swan is flying, the most noticeable sound may simply be the rhythmic beating of its wings.

Feeding and Habitat

Mute swans mainly feed by stretching their long necks beneath the surface of the water. They frequently tip their bodies forward to reach submerged vegetation, although they also dabble in shallow water and graze on land.

They favor freshwater habitats in lowland areas, including lakes, ponds, reservoirs, gravel pits, rivers, canals, and park lakes. They can also be found in estuaries, coastal brackish lagoons, and sheltered bays along the coast.

Pair Bonding

Mute swans can begin forming pair bonds when they are around two years old. They are not normally fully mature until approximately three years of age, although they may breed at that point if a suitable territory is available.

The amount of food available in an area plays an important role in determining territory size. Where common duckweed and similar food sources are abundant, breeding pairs may be able to establish territories relatively close to one another.

A mated pair will generally remain together in the same area throughout their lives and often return to the same nesting site. As long as both birds remain healthy, they will usually continue as a pair.

Conflicts over territory can become extremely aggressive and, in some cases, may result in the death of one of the birds. Although swans do not necessarily die from grief after losing a mate, they commonly experience a period of mourning. There are also documented situations in which a swan takes a new partner, particularly when a stronger cob takes control of an existing territory.

Breeding

During the breeding season, mute swans become highly territorial and will drive most other wildfowl away from the area surrounding their nest. For this reason, people should give breeding swans plenty of space when walking near waterways, especially when accompanied by a dog.

The nest is a large mound constructed from vegetation and is usually positioned close to the water's edge, often among tall plants growing along the shoreline.

Breeding generally takes place during spring. The female lays approximately one egg every other day, producing a clutch of around 5 to 12 eggs. During incubation, the female develops a completely featherless section of skin on her underside known as a brood patch.

The female removes feathers from this area and uses them to help line the nest. The exposed skin allows the eggs to remain closer to her body and receive warmth during incubation. She incubates the eggs for approximately 35–42 days and regularly turns them with her bill.

While the female leaves the nest to feed and preen, the male helps keep the eggs warm and guards the nesting area. Male mute swans do not have a brood patch and are rarely able to incubate the eggs themselves, except when the cygnets are very close to hatching.

Most of the eggs in a clutch hatch within approximately 24 hours of one another. After hatching, the cygnets remain on the nest for another day before making their way into the water. The parents help feed them by pulling up aquatic weeds and disturbing sediment from the bottom of the river or other waterway.

Protecting the Cygnets

When the cygnets are still small, they are frequently carried on their mother's back. The male can become especially defensive when an intruder approaches. He may swim toward the perceived threat with abrupt, jerking movements, holding the inner wing feathers in an arched position while drawing his neck backward over his shoulders.

Growth and Molting

Newly hatched cygnets are grey with black bills. Over their first six months, their plumage gradually develops a brownish coloration, and they learn to fly during this period.

By approximately one year of age, young swans are mostly white, although their bills remain greyish or pink. The completely white adult plumage and orange bill develop once the bird reaches maturity.

The timing of the annual molt differs according to age and breeding status. Immature and non-breeding swans molt first. Breeding females molt afterward, and the male begins his molt only once the female has completely finished and regained the ability to fly.

This sequence ensures that at least one parent remains capable of flight and can defend the cygnets if necessary.

When resting, mute swans will often pull one foot upward and tuck it against their back. This behavior may simply help the foot dry, although it can sometimes make observers think the bird has suffered an injury.