It could be any number of reasons. If there is a disruption in normal temperatures, food or other natural resources, lack of or too much water, can affect the number of hatchings. If too much rain is present or fluctuating temperatures from one extreme to another, the eggs may not provide a suitable habitat and the forming cygnets may not survive. Cygnets can even drown in these conditions. If there are predators in the area, they may have raided the nests and either destroyed the eggs or killed the cygnets.

If there are or too many swans in an area and natural resources are limited, swans have been known to practice birth control in order not to overpopulate an area. We hope that we have been able to provide some insight into this situation. The Regal Swan