If the eggs were not fertile or non-viable the parents would have abandoned the nest and other eggs. If the third egg hatched, then the parents would have taken the young swan out of the nest and moved it to another area so that predators cannot find it in the nest. The only other explanation is that one or both of the swans were scared by a predator and immediately left the area for safety. In nature, it is more important to save the parents for future cygnet production than to risk their lives for unhatched eggs.

Should you still have concerns, you might contact the local RSPCA or Swan Support in Datchet to see if there might have been a rescue in the area. If so, the swans will be returned to the same area if possible. The Regal Swan