We haven't seen the photo, but we can tell you that in nature, the chances of these species breeding would not be extremely high. Sometimes, a swan will mount another swan because it is a form of dominance in a fight and lets the other swan know that the he must cry "uncle". We have heard of individuals intentionally breeding mute and black swans to produce a blute swan (Airlee Center, Warrenton, Virginia), but again, this is not usually something that occurs naturally. So, in all probability, it was a fight with some dominant behavior being exhibited. The Regal Swan