Are the present mute swans male and female? Are the new mute swans male and female? You may have a better chance of this working out if each pair have mixed genders. In any case, you will need to build a pen (1/2 in the water and 1/2 on land with feeder inside). The pen should be covered top to bottom so that no predator can access the new birds. The new swans will need to stay in the pen for approximately 2 weeks to acclimate themselves to the new habitat, you and the other swans. Place the pen on the pond that is least used by the old pair. In a perfect world, each pair will stay on their own pond and will not stray to another which will eliminate fighting. This of course is something that you will need to watch closely so that no swan gets seriously injured during a fight nor is kept from food or water.

All of this is to say that the acceptance factor for any pair or any swan is totally an individual attribute and you will need to try out the introduction. If it does not work out, you will need to either fence the two ponds so that there is no interaction between the different pairs. If this is not possible, then any sign of aggression will mean that the new swans will need to be placed in another home. The Regal Swan