There is really no good way to do this. If you do it too soon, the female may double clutch (lay another set of eggs) which may be harmful to her health. If you do it too late, you would be killing viable young. The best thing would be to replace the eggs as they hatch with possible extra large chicken eggs. This might work and convince the female that she is actually sitting on her own eggs and obviously they are not going to hatch. Let her sit on them for a couple of weeks. When she finds out that nothing is there or you want to distrupt the nest and remove the eggs, it might cause her to go back in the water and forget re-nesting. The longer you allow her to sit on the eggs, the lower the hormone levels become and the mating need/urge will dissipate. This is why 2 male swans will build a nest and sit for a couple of weeks. Once they figure out nothing happens, they go back to being their docile selves and the urge/need to sit on the nest no longer exists. The Regal Swan