There are probably a couple of things going on here. First, this new swan is seen as an intruder because he/she was not hatched at this particular pond. Even if it had been, it is time for the juveniles to be chased from their nesting areas to form alliances with other juveniles which will ultimately lead to an eventual pairing. If the swan is chasing the juvenile is indeed a female, then the juvenile is probably a female and the older female does not want any competition. If a male swan is chasing the juvenile, it probably means that the juvenile is a male because conversely, the male does not want any competition. Usually, the opposite gender adults will not spend a great deal of energy chasing an opposite gendered juvenile. We hope this makes sense!!!

As far as introducing the new juvenile, you will need to assess if there are other juveniles that it might eventually pair and mate. If not, then this swan is going to be the odd man/woman out and will continually be chased from the pond.

If you can possibly sex this juvenile and the new rescue, and hopefully, they are either approximately the same age and opposite sex, then you might be able to introduce them on the lake with less competition for the older swans. But, there is no guarantee that the new swans will not be continually chased and/or fully accepted. The last thing that you want is to have the new swans become the aggressors and take over the pond. Finally, even if the new rescue is the same gender as the new juvenile, they may still pair if they are approximately the same age. However, if the new rescue is much older, he may seriously injure or even try to kill this juvenile so you will need another pen to introduce the two even if they are opposite gender. Swans just like all other species of the animal and bird kingdom have a hierarchy and they need to work things out, but in a captive setting, you can control the aggressiveness by slow introductions or removal from the habitat.

Yes, you need to worm your swans and it is a good idea to keep the new rescues from the older swans to ensure that no diseases/parasites are introduced onto your pond until the veterinarian can give them a good bill of health. But, once you worm one, you need to worm all of them. SInce parasites can also be introduced into your pond by wild ducks and other birds, an annual deworming is recommended. We are sending you the address of our swan veterinarians to your personal email so that you can get the exact name of the deworming medicine as well as the dosage for your veterinarian. Good luck. The Regal Swan