Mute Swans (Cygnus olor)
The swans that you see in the Worcester Swan Sanctuary are Mute Swans, and are also the most common swan seen on urban lakes/bodies of water in the United Kingdom and throughout Europe. Their scientific classification is Cygnus olor – ‘Cygnus’ being their genus and ‘olor’ being their species. They are completely white as adults, but their head can become stained a ‘rusty’ colour if they feed in acidic/iron rich waters. Their beak is orange/red as adults with a black cutting edge, tip, nostril and caruncle (also known as a ‘knob’ or ‘berry’). Their feet and legs are also black.
Mute Swan cygnets do not have the bright white appearance of mature adult swans, and their bill will be a dull greyish black, rather than an orange – this will turn a pinkish colour before going into the orange colour of mature adults. Their features range from a white to grey/buff, with grey/buff being the most common feather colour. A dull white cygnet is rare and is caused by the presence of the leucistic gene. Cygnets grow very quickly, but will typically not be their pure white adult colour until they are at least one year old.
Mute Swans can also have pinkish legs with dull white cygnets (the rare cygnet mentioned above). This is a colour morph known as immutabilitis (which is Latin for “immutable, unchangeable, unalterable”). Cygnus immutabilitis is also known as the “Polish swan”, but is only generally found in swan populations that have a history of domestication. Polish swans carry a copy of the gene that is responsible for leucism.
Mute Swan adults typically have an adult length of 125-155cm, or 50-61 inches, with males typically being lager than females. This species is one of the heaviest flying birds in the United Kingdom and in a study, males were found to average from anywhere between 10.6 to 11.87kg, with a weight range of 9.2-14.3kg with females weighing an average of 8.5-9.67kg with a range of 7.6-10.6kg.
While the name implies that these swans are not vocal, they are not actually mute, and you will commonly hear them communicating – they can even hiss when they are under perceived threat.
