There could be several reasons for the abandonment of the eggs.

1. The swan is too young and has no earthly idea how to care for the eggs. If this is the case, then next year should be better as she should have a better idea of how to care for the eggs. Placing straw in the area where you want her to nest will help. The placement should be at the time you see the swans pulling at the reeds/grasses to make a nest. Place the straw in the area that they are trying to build the nest.

2. If a predator or other disruption scares the swan, she will abandon the eggs. Even though you are on an island, turtles, mink, otters and water snakes can still access the nest and eggs which could scare her.

3. Are you absolutely sure you have a male and female swan? You may think this is a crazy question, but many times unaware buyers will either intentionally or inadvertently be sold swans of the same gender. If these swans are female, they will still mate, nest and lay eggs except the eggs will not be fertile/viable. In this case, there is no need for the female to sit on a clutch of eggs that do not have any chance of hatching and producing offspring.

4. There is something genetically/anatomically wrong with the female or male and they cannot produce fertile eggs.

If either 3 or 4 are the reasons, then the swans need to be checked by a licensed avian (bird)/waterfowl veterinarian to first ensure that they are indeed male and female. Then, if they are opposite gendered, you would then decide if you want to spend money to conduct fertility tests (this could be extremely costly).

Since the swans have already paired, the last thing you want to do is to bring in another swan (one will be left out and possibly be either seriously injured or killed) or try to separate the pair. They have apparently bonded and this separation would create problems for both in that they would look for each other and cause stress. The Regal Swan