Mute Swan (Cygnus olor): Facts, Size, Behavior and Habitat

Appearance

An adult mute swan is entirely white, though the head and neck are often stained rusty orange by iron and tannins in the water where it feeds. The bill is bright orange with a black base, black edges around the nostrils and a black tip called the nail. A fleshy black knob rises from the base of the bill onto the forehead.

The easiest way to recognize a mute swan on the water is its posture. It often holds its neck in a graceful S-curve with the bill pointing down, and it frequently raises its wings in an arch over its back. Whooper and trumpeter swans, by contrast, usually hold their necks straight and have black or black-and-yellow bills.

Males are called cobs, females pens and the young cygnets. The two sexes look alike, but the cob’s knob is larger and swells further in the breeding season. Cygnets are gray-brown with a dull gray bill for their first year, gradually turning white during their second year. Their legs and feet are dark gray.

A pale form known as the Polish swan has pinkish-gray legs and produces white cygnets. It is not a separate subspecies but a color variant caused by a gene for leucism, a condition that reduces pigment. It is found mainly in populations with a long history of domestication.

How big is a mute swan?

Mute swans usually measure 140–160 cm (55–63 in) from bill to tail, with extremes of 125–170 cm (49–67 in). The wingspan is 200–240 cm (79–94 in), wider than most people are tall.

Weight is what makes the species remarkable. Studies in Britain found that adult males typically weigh 9.2–14.3 kg (20–32 lb) and females 7.6–10.6 kg (17–23 lb). A big cob can match or outweigh a male trumpeter swan, North America’s largest waterfowl. One unusually heavy cob from Poland weighed close to 23 kg (51 lb), but it is unclear whether a bird that heavy could still fly, so that figure is best treated as an exceptional outlier.

Getting so much weight airborne takes effort. A mute swan needs a long runway of open water, running across the surface and beating its wings until it reaches around 48 km/h (30 mph) before lifting off. Once in the air it is a strong flier, recorded at speeds up to about 88 km/h (55 mph). For more giant birds, see our list of the largest birds in the world.

Habitat and range

The mute swan lives on fresh and brackish water: lakes, ponds, gravel pits, slow-flowing rivers, canals, marshes, lagoons, estuaries and sheltered sea bays. It prefers fairly large, shallow waters where it can reach submerged plants, and it adapts well to towns, city parks and reservoirs. Outside the breeding season it often grazes on fields near water.

Its native range stretches across temperate Europe and Asia, from Ireland and Britain through Scandinavia, central Europe and the Black Sea region to Central Asia, Mongolia and the Russian Far East. It is a rare winter visitor to North Africa. Birds in Britain, Ireland and most of western Europe are largely resident, while eastern and Asian populations migrate to the Black Sea, the Caspian Sea and the coasts of China and Korea in winter.

The species has also been introduced elsewhere. North America holds the largest population outside the native range, especially around the Great Lakes, the Atlantic coast and Chesapeake Bay. Small introduced populations exist in Japan, New Zealand, Western Australia and South Africa.

Diet and feeding

Mute swans are almost entirely herbivorous. Their main food is submerged aquatic vegetation such as pondweeds, stoneworts and other water plants, which they reach by plunging their long necks underwater, often tipping up like a giant dabbling duck. An adult can reach about 1 m (3 ft) below the surface.

On land they graze grasses and, in winter, crops such as winter wheat and oilseed rape. Small amounts of insects, snails and other small animals are swallowed along with the plants. Unlike some ducks, swans do not dive to feed, although adults can dive briefly to escape danger.

Because each swan eats a lot of vegetation, large flocks can strip plants from shallow lakes and bays. This matters most in North America, where the introduced birds compete with native waterfowl for the same underwater plant beds.

Behavior

Breeding mute swans are strongly territorial. On a small lake there is usually just one pair, and the cob patrols its patch of water against other swans, geese and even dogs. The classic threat display is called busking: the swan arches its wings over its back, draws its neck back and surges forward with both feet paddling together, which produces a jerky, powerful rush across the water. Read more in can a swan break your arm?

Not all mute swans live alone. Young birds that have not yet paired gather in non-breeding flocks of dozens to hundreds, often at traditional sites. In a few places with rich feeding, breeding swans nest in colonies, most famously at Abbotsbury Swannery in Dorset, England, where well over 100 pairs nest close together.

Despite the name, the mute swan is not silent. It hisses, snorts and grunts, and its wings produce a loud, rhythmic throbbing in flight that can be heard 1–2 km (0.6–1.2 mi) away. Find out more in why are mute swans called mute?

Reproduction and cygnets

Mute swans usually form their first pair bonds at 2–3 years old and start breeding at around 3–4. Pairs often stay together for many years, but separations do happen, particularly after a failed nesting attempt. See do swans mate for life? for the details.

The pair builds a huge mound of reeds, rushes and other waterside plants, often on an island or at the water’s edge, and frequently reuses the same site year after year. In Europe, eggs are laid from late March to May. A typical clutch holds 5–8 large greenish-white eggs, each about 11 cm (4.5 in) long and roughly 340 g (12 oz). The female does most of the incubating for about 36 days, while the cob guards the nest.

Cygnets hatch weighing around 180–250 g (6–9 oz) and can swim within a day. Tired cygnets often ride on a parent’s back, and in bad weather they shelter under the adults’ wings. Both parents care for the young, which take their first flights at around four to five months old. The family usually stays together until winter, when the parents drive the young away before the next breeding season.

Cygnet losses are high. Eggs and small young are taken by foxes, crows, large fish such as pike, mink and, in North America, snapping turtles. Many broods are also lost to flooding or disturbance.

Lifespan

Wild mute swans often live around 10 years, although many die younger, mostly from accidents and human-related causes. Some ringed birds have survived for more than 20 years, and swans kept in captivity can live 30 years or longer. Once past their risky first year, healthy adults have few natural predators.

Predators and threats

A healthy adult mute swan is too big for most predators, although foxes, coyotes, lynx and large eagles occasionally kill sick, injured or sleeping birds. The biggest threats are human-related. Collisions with power lines and bridges kill many swans every year, especially in flight paths between feeding sites.

Lead poisoning was once a major problem. From the 1960s to the early 1980s, swan numbers fell in parts of England as birds swallowed discarded lead fishing weights and spent lead shot. After lead weights for anglers were restricted in England and Wales in 1987, numbers recovered quickly. Other threats include fishing line and hooks, pollution, oil spills, vandalism, attacks by off-leash dogs and outbreaks of avian influenza.

Conservation status

The IUCN Red List classifies the mute swan as Least Concern, with a large and widespread population that numbers in the hundreds of thousands across its native range. In Britain, the species is protected like all wild birds under the Wildlife and Countryside Act 1981.

Its history in Europe has not always been secure. Swans were hunted heavily for food and feathers between the 13th and 19th centuries and disappeared from much of western Europe, surviving in places such as England partly because they were kept as semi-domesticated, owned birds. Protection in the late 1800s and 1900s allowed the species to recover across its former range.

In North America the situation is reversed. Mute swans spread rapidly after their introduction, at least 10% a year in the lower Great Lakes between 1971 and 2000. Several US states treat them as invasive and manage their numbers to protect native water plants and birds such as the trumpeter swan.

Myths and facts

Myth: a swan can break a man’s arm or leg with its wing. A swan’s wing is strong and its blows can bruise, but there is little reliable evidence of swans breaking adult bones. The real risk is being knocked off balance, especially near water.

Myth: swans always mate for life. Most pairs stay together for years, but divorce does occur, and a widowed swan usually finds a new partner.

Myth: all swans are royal property. The British Crown claims only unmarked mute swans on open water, and today it exercises that right only on parts of the River Thames. Read does the King own the swans?

Myth: mute swans sing before they die. The “swan song” is an ancient legend, not observed behavior.

Relationship with people

Few birds are as tied to human culture as the mute swan. It is the national bird of Denmark, adopted in 1984, and the hero of Hans Christian Andersen’s fairy tale “The Ugly Duckling.” In England, swans were a luxury food for medieval banquets and were marked as property, which led to the royal ceremony of Swan Upping that still takes place on the Thames every July.

Mute swans have been kept in ornamental waters for centuries, which is how they reached North America in the late 1800s. Today they are among the most familiar wild birds in European towns, where many become used to people on busy park lakes and riverbanks. Giving swans space, especially in spring when they are nesting, keeps both birds and people safe.