It is a sound that stops me in my tracks every time I hear it – the unmistakeable throbbing hum that emanates from the giant wings of mute swans as they fly over Sudbury.
It is a signal to look up and see the marvellous sight of these snow-white creatures speeding through the air, their long necks protruding so far out front they seem barely supported.
It is said this sound, which is unique to the mute swan, can carry for more than a mile and may help the birds communicate with each other. It is ironic, then, that these animals capable of such resonance have earned the name mute swans. For they are not silent at all – they also produce a range of hissing and grunting noises - but are relatively quiet when compared with whooper and Bewick’s swans, two other similar species, which are not native to the UK but travel to these shores in winter from Scandinavia and Siberia, respectively.
Unlike these seasonal guests, our native mute swans do not tend to voyage far at all. A few years ago, volunteers from the East Anglian Swan Study group visited Brundon Mill to put rings on swans’ legs, as part on their ongoing tracking study into mute swan behaviour.
Their studies had shown that adults will stay within a local area of a couple of miles, while youngsters tend to travel a bit further afield – within a vicinity of 10 to 15 miles – and often between two sites. The theory is that immature swans do this to get to know their area and build up a mental map of the neighbourhood.
This stretch of the Stour has a special relationship with swans. Sudbury and many of its surrounding villages – Henny, Bures, Long Melford, Lavenham, Little Waldingfield, Clare - have or have had a pub or hotel named after Cygnus olor.
Swans are now such a fixture on the Common Lands that it is easy to take their wonderful presence for granted, especially because they have become semi-domesticated and are quite tame. Today there are close to 100 swans on and around the Common Lands – a number that is artificially high because people feed them. Even so, the total is in sharp contrast to thirty years ago when there was only one pair.
This was a period when water pollution was a problem, as was lead poisoning from lost fisherman’s weights. A swan requires grit to break down food and picks up gravel from riverbeds, which it stores in its gizzard. The birds would inadvertently take up the weights which would gradually be absorbed into the body and cause lead poisoning.
Although the use of lead shot for fishing is now illegal, a residue still exists. In the 1990s the river near Sudbury was dredged, disturbing some old lead, which resulted in a swan nearly dying.
Mute swans are territorial, and alpha cob (male) swans hold territory in different areas of the Common Lands. Every spring they must fend off other male swans who challenge them for territory and mating rights. Many of the males who fail can be seen congregating at Brundon Mill where they continue their constant battle for one upmanship - nibbing other swans’ necks with their beaks and driving through the water with their wings curved up to intimidate rivals.
Knobs and nests
Male and female mute swans can be difficult to discern. Males tend to be larger, as does their basal knob, the name of the mysterious bump located at the base of the bill. Experts are not certain about the purpose of the basal knob, although it is believed they may serve as an indicator of health or sexual maturity, particularly during the mating season when they become larger.
The male and the female birds, the cob and pen, usually attempt to mate for life. Regular users of the Common Lands will have seen their huge nests made from assorted vegetation, sticks and rushes, constructed at the water's edge. The nest is built by the female, while the male supplies the materials.
Mute swans can be aggressive in defence of their nests and are highly protective of their mate and offspring. Most defensive attacks from a mute swan begin with a loud hiss and, if this is not sufficient to drive off the predator, are followed by a physical attack. Swans attack by smashing at their enemy with bony spurs in the wings.
It is imperative that dog owners are aware of this and keep their pets on leads near swans. The Commons Lands is their territory and each year our rangers receive reports of dogs attacking swans.
Kayakers and canoeists should also try to give swans a wide berth, especially if they are with their cygnets. My wife and I were once capsized after a swan took a run at us across the water – we managed to drag ourselves to the bank and consoled ourselves with a restorative drink at the nearest pub…. fittingly the Henny Swan.