We are so sorry for your loss. After reading your update, we actually thought by going into a back area for a bit, he was sitting next to a nest with her. Obviously, this was not the case and he was looking for her. Were there any signs of trauma?

If her demise was due to a predator, there would be obvious signs of trauma, or if she had been shot or beaten by someone. If no trauma, she could have died from a myriad of possibilities to include egg impaction, infection, age, etc.

Unless a necropsy is completed, there is no way to determine what caused her to die.

Do you know the age of the pair? They may have been an older pair and age caught up.

You may entertain the idea of getting him another mate, but this may not be the best solution. It may be better just to feed him, watch him and let him live his life without a new mate. There are no guarantees that he will accept a new mate as most males will not re-pair and this is totally a species and individual trait. If a predator is in the area, the new swan will not know how to protect itself and may meet the same end if a predator was the cause. Again, we feel your loss, it is not easy to have such a beautiful life come to an end. The Regal Swan