Not sure what is occurring. If you are not watching the swan for a length of time (consistently 2-3 hours), then it is hard to tell if she might be leaving the nest to eat, drink and bathe. If you are just driving by intermittently, then the swan may have already left the nest and has returned to incubate eggs. Again, nature is not going to allow any bird or animal to remain at the nest/den area if there are no viable offspring. Also, female swans will lay eggs regardless of the presence of a male, even though the eggs are not viable. Eventually, the swan will leave the nest if this is the case.

Is there any way that you can get close enough to the nest to see if she will get up or leave the nest to see if there are eggs? If not, then nature is going to have to take its course and the swan will leave when it is ready. The Regal Swan