Never worked for me

Maybe a call duck pair.. It's still nice to have more than just one hen, Especially if she were to lose one of the two. Then you'd have to go through all that trouble to find a new buddy for a lonely duck and introduce new birds together. And because
@HuffleClaw 's duck is crested i'd definitely get more hens for the drake to breed with, If he grabs onto the duck's crest too hard he can cause serious damage to her since the "Crest" is really just fatty tissue covering a gap in the skull covered by feathers..