How long has the mother swan been away from the eggs? If there is any significant time, (more than 2 hours), then you can safely assume that she is not going to take care of eggs that have not hatched. Her attention must go to the viable offspring to ensure that they survive.

If the mother swan has left the eggs for a significant time, then you can take the eggs and toss them into the pond. DO NOT place them in a trash can or bring the indoors as they can explode into a stinky mess. By getting rid of the eggs, you also prevent pests such as ants and rats or predators being attracted to the nest. This is of utmost importance especially if the mother is bringing the cygnets back to the nest at night. The Regal Swan