Question about call duck pairs

[denise91]

I've got two pairs of call ducks. The first pair is Daisy and Mr. Crankypants (he bites) and the second pair is Not Daisy and The Other Male (we couldn't figure out what to name them so we just didn't). Each duck is inseparable from their respective mate. Except when it comes to actually mating. Mr. Crankypants will only ever mate with Not Daisy. Not Daisy isn't particularly bothered by this nor is The Other Male. But the real Daisy gets upset and will erm "present" herself to Mr. Crankypants but he ignores her. The Other Male only ever mates with Daisy. Mr. Crankypants got a little upset by this at first and would gently hold on to the back of The Other Male's neck as if to say, "Please stop doing that." Well now both males only ever mate with the wrong females and no one really cares. But when they're not mating Mr. Crankypants never looks twice at Not Daisy and The Other Male never looks twice at Daisy.

I hope this all makes sense. To break it down easier: the ducks refuse to consummate their marriages but they have no problem conducting illicit affairs.

Is this normal behavior? Could it be potentially hazardous in any way?