Once the cygnets of an older age, the parents may separate for a couple of days, usually to the other side of the pond, but since you may live in an area with long areas going into separate streams, rivers or creeks, there is a possibility that the other swan, probably the male has gone off to forage in another area. His duties are over. Usually, they will return as long as he has not been injured or taken by illness or predation. So, more than likely, he will make his return shortly.

There is also the possibility that he is in the immediate area, but just not in sight during the time that you are taking your walk. The Regal Swan