A Mallard - Tufted Duck Pair?

On Saturday, Zoe and I noticed this female mallard and male tufted duck on the top lake.  They were going around together as if they were paired up for breeding: when the tufted duck walked off along the bank the mallard did the same, when he got into to the water she followed, and when she flew away, he flew after her.  I understand that tufted ducks do hybridize with pochards and scaups but I can't find any references to them doing so with mallards.  It will be interesting to see if they have any offspring and, if so, what they turn out like.