There could be several reasons that the eggs are not fertile:

1. The swans are not old enough to fertilize the eggs. This is especially true of swans 1-2 years of age. Some swans at 2 years of age can produce cygnets, but others may not. If the birds are over 2 years of age, then the following reasons may come into play.

2. There is something wrong with either bird (anatomically or genetically) so that they cannot produce viable offspring.

3. You have two females. Have you had your swans checked by a licensed avian/waterfowl veterinarian?

The least reliable method of determining gender is probing. If the swans are less than 1 year of age (and even in some cases, less than 1 1/2 years of age), the genitalia may not be developed (this is especially true in the male swans). For this reason, swan keepers/owners may think they have a certain gender, but find out later when the genitalia is developed that they have a different gender.

The most precise method is to take a feather sample and conduct DNA Sequencing. The veterinarian will need to take a sample of a feather with some blood on the end and submit it to a reliable DNA lab. The swans and the sample will need to be identified so that when the results come back they match with the perspective swan that the sample was taken. The lab will provide you with the results and you will know for sure. The Regal Swan