Where To Find Swans
Swans are much easier to find these days. They are present throughout the British Isles. Indeed, it is likely that they have always been here, to a greater or lesser degree. At the moment, there are at least 31,700 in this country (up from about 17,600, in 1978) and the numbers are increasing.
Why are there more Mute Swans about these days?
In no particular order, the main reasons why the numbers of swans is going up are:
The banning of the use of small lead weights, used by fishermen. Swans swallow particles of grit to aid in the digestive process of their food. They used to take in the lead shot, mistaking it for grit, it would then reside in the gizzard and cause the bird to become poisoned. The muscles would become weaker and weaker, and the swan would die as a result of malnutrition (i.e. starvation) and muscle failure. As a result of the lead shot ban, this problem has now been very much reduced. (Incidentally, the vast majority of fishermen appreciate the wildlife around them and would never choose to go back to using small lead shot because of the negative impact it would have on the swans and other wildlife.)
In 1981, a Wildlife and Countryside Act was passed which had the effect of affording greater protection to swans and other wildlife. This has meant that mistreatment and cruelty towards many animals has been in a downwards trend since then.
In the increase in intensive agriculture over the past few decades. This has meant that farmers have increased their use of fertilizers, which has increased the supply of high quality food that the swans make use of in winter. And winter is when they need agricultural areas the most, since they need to eat more to sustain their high body temperature in the cold weather conditions and some of their natural food, like the streamer weed in rivers, has died back significantly.
On a more local level, you can locate Mute Swans in (in order of preference) shallow freshwater stillwaters, slow and medium paced sections of rivers, deep freshwater stillwaters, estuaries and the sea.
The key requirements are an abundance of food (hence preference for shallow water over deep because they can only reach down about a 1m) and enough space to form a territory.