Unfortunately, the male black swan may have gotten familiar with the female black swan, but was not introduced properly to the other swans on the pond. It was also introduced at the wrong time of the year (nesting/mating season) in which the testosterone levels are high and defensive behavior much more prevalent.

You must build a pen (1/2 in water and 1/2 on land, zero entrance and totally enclosed top to bottom so that predators cannot dig under or climb into the pen). A feeder should be placed in the pen and the new swan kept in the pen for approximately 1-2 weeks to acclimate it to its new habitat, the female swan, you the caretaker, and the white swans. You should observe for any aggressive behavior on behalf of the white swans.

If this behavior continues, you need to find the male black swan another good home and just leave the female black swan alone. She will do just fine, but you do not want to risk the possibility that a new swan will get seriously injured or killed by any of the swans. If there is no aggressive behavior in the next two weeks, then you can tentatively place the black swan onto the pond.

Ensure that you have a kayak, boat or other rescue/capture equipment available should the situation turn aggressive and a rescue needs to be effected. Again, any sign of aggressiveness (which we would rather call defensiveness-as the male swan is just protecting his habitat and family against someone who he does not know), necessitates that you find the male black swan a good home. The Regal Swan