October 2011 - Mute Swans
The mute swan is called ‘mute’ because it is not a vocal species. We have all seen these swans on the river by the mill in Bawburgh. These beautiful large white birds, with long S-shaped necks fly with a unique vibrant throbbing of the wings, the sound of which is heard several moments before the swan can actually be seen. The only other sounds you may hear are hissing as the birds vigorously defend their territory, or the occasional grunting, hoarse sounds as they communicate especially with their young. The male (cob) can be distinguished from the female (pen) by the larger black knob on the top of its orange bill. Young birds (cygnets) develop the white plumage when they are about a year old, up to this age they maintain a grey/light brown colour. As their plumage changes to white, their bills change from the juvenile greyish colour to the orange of the adult. Rarely a cygnet may be white from the time of hatching and then it is called a ‘Polish swan’.
The swan with its long neck is well adapted to hunt for food consisting of vegetation, aquatic insects and snails found at the bottom of rivers or lakes. Occasionally they will graze on plants by the side of the river.
Mute swans pair for life unless one dies, then the one left may take another mate. Nests of assorted vegetation, sticks and reeds, supplied by the male, are built into large mounds by the female at the waters edge. Both sexes incubate the eggs and feed the young. Cygnets may sometimes be seen riding on the backs of their parents. The family group may stay together for 4 or 5 months. Young adults are eventually driven off to start lives on their own, but will not start to breed for at least 2 years.
One main threat for swans is pollution of their habitat by anglers’ lines (causing entanglement) and lead weights. The latter may be taken into the gizzard with the grit needed to aid digestion and will eventually be absorbed into the bird’s body causing lead poisoning. The use of lead shot is now illegal, but discarded pellets are still found. Other threats come from overhead power lines or from vandalism.
6,000 year old fossils of swans have been found in East Anglia. Let’s hope swans will be around for the next 6,000 years as well.
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