You need to get him to an avian (bird), waterfowl or exotic veterinarian ASAP. When birds or animals go to sit by themselves and stop eating, there is usually something seriously wrong, i.e., injury or illness which can lead to death. Swans can live up to 30 years in a great setting, still 25 years is a rich life for a swan.

He cannot continue to not eat and the veterinarian may need to tube feed him, give him an i.v., provide him with a B-12 shot to stimulate eating, provide an antibiotic if needed or some or all of the above based upon his exam. The most important issue at this time is to get him to a licensed veterinarian with bird or waterfowl experience to see what is occurring. The Regal Swan