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Mute Swan (Cygnus olor) and Polish Mute Swan (Cygnus immutabilis)

mute

This is the most common swan seen on our urban lakes and in Europe.

A family of Mute Swans

Description: The adults are completely white, but the head can be stained rusty from feeding in acidic waters. The bill is orange-red with black nail, cutting edge, bill-base, nostril, and fleshly frontal knob. Legs and feet black, but remain pink on ‘Polish’ birds. The Juvenile: bill lacks frontal knob, pinkish-grey, with black areas as adult becoming pinker during first winter and attaining adult shape and colour by second winter. Legs and feet grey or pinkish-grey on the Polish swan.

Field Identification:

Length 125-155 cm (50-61in).

The males are usually larger than females.

In Flight: The typical swan shape, most easily distinguished in flight by clearly audible throbbing drone ‘waou, waou waou’ produced by the wing-beats. Hardly vocal in flight, apart from occasional grunts. Pointed tail projects beyond prominent black feet, in northern species feet reach tail-tip, but if a bird is close enough to see this feature bill is also visible.

Voice: as the name implies, least vocal of swans, but by no means mute. Utters short grunts and hisses, also during breeding period short, loud snorts, but lacks honking flight calls of other species.

Habits: We find this swan on most of our lakes, rivers and ponds, both in open country and about towns and cities. They are generally tame, but wild birds (in Asia) are wary and unapproachable. It has long been domesticated particularly in Britain, where its history dates back to the twelfth century; also domesticated by the Greeks and Romans. Normally strongly territorial in the breeding season, driving most other wildfowl from the vicinity of nest, but in some places large numbers breed in close proximity to each other, as at Abbotsbury, Dorset, in England.

The nest is a huge mound of vegetation, close to the waterside, often among tall fringe vegetation. Breeding commences in April, but introduced populations in South Africa breed in September and October. Cygnets, when small, are often carried on the back of the female. Male will be aggressive, swimming in jerking movements towards intruder, with inner wing feathers arched and neck resting back on shoulders. After breeding they form large concentrations on selected waters for post-breeding molting.

Feeds primarily by reaching below surface with long neck, frequently upending, but will also dabble and graze on the land like other swans of the Northern hemisphere.

Habitat: Favours lowland freshwater lakes, pools, and reservoirs, gravel-pits, rivers and park-lakes. Also on estuaries, coastal brackish lagoons and even in sheltered coastal bays.

Population: European population increasing with local introductions continuing, though in parts of Britain species has shown serious decline recently, mainly caused by poisoning from swallowing anglers’ discarded lead weights.

Polish Mute Swan

The polish mute swan is a ‘pure white’ version of a mute swan. The legs and feet are a pinkish-grey colour instead of the usual black colour.

A pigment deficiency of a gene in the sex chromosomes is what causes the whiteness.

When a female mute swan inherits only one melanin-deficient chromosome she will be a polish swan, whereas the male of the same parents will be normal. If the next generation is produced by two of their offspring the brood will contain numbers of both polish and normal cygnets of either sex.

Polish swans were given their name when they were imported from the Polish coast on the Baltic sea into London around about 1800. Mistakenly thought to be a new species they were given the name ‘Cygnus immutabilis’ (changeless swan).

Polish swans are not a different species of swan, because they are mute swans.