A couple of scenarios come to mind. Usually, swans will discard eggs that are not fertile or rotten. The swans obviously know when something is or is not viable, otherwise they would spend an inordinate and useless amount of time sitting on eggs that will never hatch.

The first scenario would be that the swan accidently ditched some viable eggs out of the nest along with rotten eggs and tried to recover the good ones by gathering them and starting a new incubation site directly on the ground.

The second thought would be that there was something wrong with the nest, i.e., maybe water being taken on and the swan was trying to get the viable eggs out of the nest to save them. Obviously, something else could be occurring, but these are the only scenarios that make any sense. We hope that this information is of benefit. The Regal Swan