You need to take the female swan that was separated from its mate and let whomever you bought it from reunite the pair. It is going to be extremely difficult to allow an odd bird out from a mating pair. Eventually, the pair will try to chase the odd bird out of the habitat, especially during mating season and this can cause the swan so much stress that it can die from dehydration, starvation, or illness. You need to find a male that is young and not paired with another swan.

Even then, there are no guarantees that your swan will re-pair with another swan. Usually, female swans will re-mate, but this is going to be a trial situation on your part. The Regal Swan