Well, here is one of those stranger things have happened moments! Are you sure there are no male swans in the area? This may not be her only egg. You need to check the nest again tomorrow and the next day, because swans usually lay eggs, one every other day.

If she does not lay any more eggs, incubation will probably start right away. If there are more eggs laid, incubation will not start until the very last egg is laid. She will usually know that nothing is happening as far a viability within the next 3 weeks. Raccoons, foxes, coyotes and other predators could try to get to the eggs and possibly harm her.

If you are really concerned about her safety, we would go ahead and capture her as she sits on the nest. She will defend the nest by flailing her strong wings, so you need to be extremely careful so she does not hurt you or herself. A large salmon net would be the best device for capturing her on the nest, unless you can grab her neck and place your hands immediately on the wings to prevent the wings from striking you.

Once she is captured, we would suggest keeping her in a garage (free from gas and chemicals) Water and food (poultry layer pellets and cracked corn submerged in water as well as lettuce) in a large bowl should be available. Give her a couple of days and she'll forget about the nest and go about her business.

If she tries to re-lay eggs, at least she may be smarter regarding the location of the nest and learn to keep it away from predators on lands, such as humans. This location will also help protect her from land predators such as the raccoons, etc. Hopefully, she will learn to build a nest on an island or very marshy area where land animals cannot access her and the nest.

Of course, once you capture her, she may never trust you again, or at least, not for a long while. The Regal Swan