Ask the Swan Specialist
Date: 12 April 2016
Thank you for your kind words. We are glad that the website is of benefit to you.
There could be several explanations for the loss of the eggs. The swans do not necessarily need to feel movement, they can also feel temperature, etc. and know when eggs are not viable. If you had an extreme temperature swing, the eggs would have been warm, then cold and back to warm again or never rewarmed. Temperature swings are not good. If the eggs were not warm and the swans sensed something was wrong, they would have rolled them out of the nest and into the surrounding water where turtles and fish would eat the eggs.
If the swans did not remove the eggs, then there is always the possibility that a predator, (snake, fox, coyote, raccoon, opossum, armadillo, etc.,) took the eggs and ate them.
Did you check in the bowl of the nest under the nesting material in the center of the bowl? Sometimes, the mother swan will bury the eggs under the nesting material so that they cannot be readily seen by humans or other predators as she takes a break from the nest to bathe, feed and preen. If she returns to the nest, then there is a possibility that this is indeed the case and she will continue nesting. If she refuses to go back to the nest, she either knows that the eggs were not viable or that a predator is present and she is not going to place her life in danger. In nature, the parents will not risk their lives for unhatched/unborn offspring. They need to live another day/year to produce more eggs and ensure the continuation of the species. The Regal Swan