Our Animals - Mute Swan
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The Mute Swan (Cygnus olor) is a species of swan, and thus a member of the duck, goose and swan family Anatidae. It is native to much of Europe and Asia, and (as a rare winter visitor) the far north of Africa. It is also an introduced species in North America, Australasia and southern Africa. The name 'mute' derives from it being less vocal than other swan species. Measuring 125 to 170 centimetres in length, this large swan is wholly white in plumage with an orange bill bordered with black. It is recognisable by its pronounced knob atop the bill.
Adults of this large swan range from 125 to 170 centimetres (49 to 67 in) long with a 200 to 240 centimetres (79 to 94 in) wingspan. They may stand over 120 centimetres (47 in) tall on land. Males are larger than females and have a larger knob on their bill.
The Mute Swan is one of the heaviest flying birds, with males (known as cobs) averaging about 12 kilograms (26 lb) and the slightly smaller females (known as pens) weighing about 9 kilograms (20 lb). An unusually big Polish cob weighed almost 23 kilograms (51 lb), surpassing the longer-bodied Trumpeter Swan to make it the heaviest waterfowl ever recorded. Its size, orange-reddish bill and white plumage make this swan almost unmistakable at close quarters. The most similar species is the Whooper Swan, but it has a yellow and black bill, lacks the curved neck, is longer and heavier, and lacks the characteristic projection above the bill.
Young birds, called cygnets, are not the bright white of mature adults, and their bill is dull greyish-black, not orange, for the first year. The down may range from pure white to grey to buff, with grey/buff the most common. The white cygnets have a leucistic gene. All Mute Swans are white at maturity, though the feathers (particularly on the head and neck) are often stained orange-brown by iron and tannins in the water.
The morph immutabilis ("Polish Swan") has pinkish (not dark grey) legs and dull white cygnets; as with white domestic geese, it is only found in populations with a history of domestication.
Mute Swans are not always territorial. Where food resources are adequate they will form dense flocks.
Mute Swans nest on large mounds that they build with waterside vegetation in shallow water on islands in the middle or at the very edge of a lake. They are monogamous and often reuse the same nest each year, restoring or rebuilding it as needed. Male and female swans share the care of the nest, and once the cygnets are fledged it is not uncommon to see whole families looking for food. They feed on a wide range of vegetation, both submerged aquatic plants which they reach with their long necks, and by grazing on land. The food commonly includes agricultural crop plants such as oilseed rape and wheat, and feeding flocks in the winter may cause significant crop damage, often as much through trampling with their large webbed feet, as through direct consumption. Unlike Black Swans, Mute Swans are usually strongly territorial with just a single pair on smaller lakes, though in a few locations where a large area of suitable feeding habitat is found they can be colonial. The largest colonies have over 100 pairs, such as at the colony at Abbotsbury Swannery in southern England, and at the southern tip of Öland Island, Ottenby Preserve, in the coastal waters of the Baltic Sea, and can have nests spaced as little as 2 metres (7 ft) apart. Non-mated juveniles up to 3–4 years old also commonly form larger flocks, which can total several hundred birds, often at regular traditional sites. A notable flock of non-breeding birds is found on the River Tweed estuary at Berwick-upon-Tweed in northeastern England, with a maximum count of 787 birds. Once the adults are mated they seek out their own territories and often live close to ducks and gulls, which may take advantage of the swan's ability to reach deep water weeds, which tend to spread out on the water surface.
The Mute Swan is less vocal than the noisy Whooper and Bewick's Swans; the most familiar sound associated with Mute Swan is the vibrant throbbing of the wings in flight. This sound is unique to the species, and can be heard from a range of 1 to 2 kilometres (0.6 to 1 mi), indicating its value as a contact sound between birds in flight. They do however make a variety of grunting, hoarse whistling, and snorting noises, especially in communicating with their cygnets, and usually hiss at predators trying to enter their territory.
Although this bird can be tame, especially to those who feed it daily, it is aggressive in defence of its nest, and its size and impressive hissing make it a formidable adversary for animals as large as a fox. Large waterfowl, such as Canada Geese may be driven off, and there have been many reports of Mute Swans attacking people who enter their territory. The cob is also responsible for defending the cygnets while on the water, and will sometimes attack small watercraft, such as canoes, that it feels are a threat to its young. The cob will also try and chase the predator out of his family territory, and will keep animals such as foxes and birds at bay.
The familiar pose with neck curved back and wings half raised, known as busking, is a threat display, mainly shown by males but also females to a small extent. Black Swans and Whooper Swans are less aggressive and are not as defensive against predators. Trumpeter Swans will sometimes leave their nests if threatened. Mute Swans will attack land animals in defense of their families, during the period before fledging of their offspring[vague] (which, at six months, is longer than that of most other birds).