There are several factors to consider in this situation:

1. Just because a female or male loses its mate, does not necessarily mean that the swan will remate if introduced to another swan.

2. How did the male swan die? Was it natural causes (old age), predation or something in the water, i.e., botulism, poison, etc.? This factor is a big issue because old age is going to happen to the female swan whether you move her or not. If she is an old swan, then she probably needs to be left on the existing pond. If the male swan was a victim of a predator or illness caused by something at the pond, then you need to move the female to another location.

3. How long have you had the swans? If you have had the swan for more than 1-2 years, the bird is now comfortable with this home and even you. To transport to another lake/pond, may work, but it would be like you moving to another location with no friends (i.e., swan keepers, etc.). Is there a possibility that the new owners will take care of her or the surrounding neighbors (anyone that she is used to being around)? Again, this is a moot point if a predator or something in the lake caused the demise of the male swan. The female needs to be moved in this instance.

4. Any chance that you can take her with you to your new location so that she can continue to be around you?

The only other viable solution is to go online to see if any waterfowl sanctuary, wildlife rehabilitation center might be able to relocate her to another pond and other swans. Good luck. The Regal Swan