What you observed may or may not have been mating behavior. If it was indeed mating behavior, the two swans will eventually find each other and start to build a nest. If the swan that was on top exhibited a certain behavior, i.e., spread his wings, stood up and became vocal (triumphant sign), then it was probably a male. However, this same behavior (which does not involve mating) but will have a dominant male jump on top of another male to show dominance and chase him from the area. The dominant swan will also display this behavior to show that he owns the territory. In this case, the two swans will usually not return together as one will be seriously hurt if not killed.

If the swan was trying to hold the other swan's head above the water while on top, then this usually indicates mating and will only take approximately 30 seconds. The male will hold the female's neck above water during copulation so that he does not drown her under his heavier weight. We hope this information helps clarify what you observed. The Regal Swan