The swan may have something wrong with it so that it cannot fly or is extremely tired from the long migration. If it can, it will rest and then gets its strength to move on. As long as there are ducks and other waterfowl, it means that there is a good food source for the swan.

Did the swan arrive in the area with the flock or was it in the area by itself when the other swans arrived? If it was by itself, it may or may not leave. If it came in with the other swans, then it will probably leave on its own.

If it does not leave, are there any predators in your area that may attack the swan at night or at other times when it is not in the body of water? If so, then it may not have a good chance of survival. Also, depending on your location, the swan's demise might be met by your state and federal wildlife officials who intentionally kill Mute Swans so that they can free the habitat to introduce the larger Trumpeter Swans for Trophy Waterfowl Hunting purposes. If this is the case in your state, you need to discretely check around wildlife rehabbers/facilities to see if they might be able to intervene and check the swan out so that they do not kill the swan under the orders of the wildlife officials. The Regal Swan