Yes, it is normal as the other swan may be searching for another habitat, especially if the swans need better resources such as shelter and food for the upcoming inclement winter weather.

Also, these may be young swans who have not yet paired and are just finding their way around your area. If they are paired and nothing happened to chase the other swan away, i.e., predator, another swan family, etc., then they should reunite shortly. The Regal Swan