What are my ducks doing in their pond?

I have three ducks one is a mallard,one is a pecan, and one is a Blue Swedish . I don't know their genders but I always used to think that my pecan was the male because he would lead them all around. That's what I thought but yesterday i looked out to see my blue Swedish on top of my pecan in the pond. I thought how weird are they mating but my blue Swedish only stayed on for 10 seconds. so i was wondering if my ducks are confused or if they know what they are doing and whos a female and who is a male. The two that were mating are seven months old and my mallard is about 3 or 4 months old