The swan will do just fine by itself, especially if it is pinioned (rendered unable to fly and in a captive setting). Reintroducing a mate, takes approximately 2-3 weeks with the new bird being placed in a pen (1/2 in water and 1/2 on land with a feeder inside the pen). You will need to capture the remaining swan and have it sexed to determine its gender. DO NOT Place two males or two females together, especially if the swans were older swans. Same genders will usually not get along after having a prior mate.

The older inhabitant of the pond needs to be observed to insure that he/she is not showing any signs of aggressiveness toward the new bird and vice versa before the new swan is released onto the pond. Even then, there are no guarantees that the remaining swan will take a new mate. In fact, most male swans will go about their lives with no problem. Females, will usually re-pair, but not always. So, even if you get another swan there are no guarantees that they will get along which means you will need to find the new swan a good home. The Regal Swan