Do not disturb the nest. Mama knows best and since you don't know when they hatched, it is extremely important that the mother stays with the cygnets. If you disturb the nest, she could leave the cygnets and abandon everything. Usually, she will get the cygnets in the water and away from the particular nest within at least 2 weeks. She will gradually wean them from the nest taking them for longer swims and farther away from the nest. For the first 2 weeks, she will bring them back for naps and overnight.

If nothing else hatches by the time she begins to leave the nest for longer periods and you notice eggs still in the nest, then remove the eggs so that she will concentrate on the hatched cygnets and not the unhatched. The key is to make sure that nothing else is hatching. Should something hatch and she abandons the cygnet for the older brood, there is not much you can do. If you intervene, you will have a cygnet that can imprint on you and you may have greater problems than just letting nature take its course.

Should there be any genetic anomalies, they will occur years down the road. This is usually not a big issue in swans or other birds. The Regal Swan