Are the Muscovy Ducks someone's pet or belong in a nearby captive setting? If so, you may be able to capture them and take them to their owner and request that they be kept on their pond. If this is not the case, and the ducks are a wild (feral) flock, then there may not be much you can do as many years ago they were listed as a protected species. Go figure that the Federal Wildlife Service officials would protect the Muscovy Duck and not the Mute Swan.

In any case, one possible solution to this issue is to build a nesting pen (completely enclosed top to bottom so that predators cannot crawl over or dig under to access the swans). The nesting pen would need to be 1/2 on land and 1/2 in water with no steep bank, but a zero entrance with a feeder enclosed in the pen. The outside perimeter of the pen must be covered on the outside from the bottom rail up to 4 feet with plastic poultry fencing so that the cygnets cannot escape through the pen away from the parents or be grabbed by a raccoon or other predator through the pen. Of course, you will need someone to build the pen and service the feeder on daily or weekly basis depending on type of feeding system. The major problem with this solution is that the swans may not nest or lay eggs in a pen.

Another possible solution would be to see if there is a wildlife rescue facility in the area. They may be able to take the Muscovy Ducks and relocate them to a safe home, but again, they would need to ensure that if they relocated the ducks that they would incur no harm and they may possibly need a relocation permit. The Regal Swan