This is the time for mating/nesting. Female swans will mate and produce eggs (non-fertile obviously) and sit on a nest. The swans' hormone levels are high and out of control. Once the nesting season ends, everything should go back to normal. The first thing that must happen is to have the swans nest and get it out of their system. With or without eggs, the swans will sit for approximately 2 weeks or until their hormone levels go back to normal or they get bored with sitting for no reason.

If the defensiveness continues, you may want to see if there is something in the habitat that changed, i.e., presence of something new in the habitat, human agitation, (spraying of the pond/changing out or clipping vegetation), or presence of domestic (dogs/cats) or wild predators, etc. If this is the case, then these issues must be mitigated or the defensiveness may take longer to dissipate and one or both of the swans may get injured. The Regal Swan