Just to let you know that we have caught your cygnet in our kayak. He has avian botulism - this is NOT contagious to humans or from live bird to live bird. It is caused by bacteria in the silt which produce a toxin called Botulinum. This is the same toxin used in Botox treatments, and causes paralysis of the muscles. As a result, the muscles which keep the wings in place become paralysed, which causes them to drop into the water (this is the very first sign). Eventually the muscles in the neck which prevents them from eating and drinking become paralysed and the bird becomes weaker. He will be taken to The Swan Sanctuary where he will be placed on a drip.
Please please keep an eye on the rest of the swan family, if one is sick then there is a patch of silt somewhere where the toxin is, so it's possible they will become unwell too. Please keep them well fed - things which float like bread (yes, bread is perfectly fine unless it's mouldy), or swan pellets. Do not feed grain or corn or things which sink, unless on the bank, as then the birds have to dig in the silt to eat it.
Louisa Green
The Swan Sanctuary