Predators could have gotten the eggs, i.e., raccoons, turtles, ect. More than likely, a human took the eggs either to start their own swan collection or thinking that removing them, they would prevent further hatchings. Unfortunately, it probably did not prevent hatchings because the female will more than likely, lay more eggs to replace those that were lost. This doesn't always occur, but usually it does because the pen come into the world with a set number of eggs that she is to lay and she can count. Let us know if she has more eggs. The Regal Swan