Thanks for the nice comments. Usually, the male is responsible for building the nest, but nature tells swans when it is nesting season, so the bird knows that it is supposed to have a nest and has made one. Females may lay eggs if there is another swan (male or female)but obviously, not fertile eggs if there is no male. The only way to know if there are eggs is to look into the nest, but again, if there is no mate, the eggs will be infertile. Realistically, in this case, you would need to get the bird to a veterinarian and have it sexed to determine the sex. The Regal Swan