Yes, female swans will still lay eggs (obviously non-fertile) during the nesting season and sit on the eggs and nests until they get tired of sitting and realize that nothing is going to hatch. Conversely, male swans will also nest, but will obviously not lay any eggs. All swans have sex hormones that increase during the mating/nesting season which cause them to increase their mating and nesting behavior. So, all of the behavior you are seeing is normal in a swan’s world. The Regal Swan