Yes, it seems that each swan as a built in number of eggs produced on a yearly basis throughout her lifetime. This is why if you remove eggs, they can count and may try to double clutch to replace the eggs. This is not good for the female as she will lose approximately 30% of her body weight during the nesting process.

Depending on the individual swan and the species, the male will sit on the nest or nearby while the female swan takes a break to swim, eat and rest. The closer to hatching, the less time that the female will stay from the nest. The Regal Swan