Are my mallards girls or boys?

[Yaypekinducks]

My mallards both seem to be quacking (and still peeping), sort of. I thought they were girls but I just noticed that they have a subtle green tint on the top of their head, so I don't know if they're male or female.

 

[Yaypekinducks]

Their wing feathers haven't grown in.

 

[Isaac 0]

If their both quacking, that means their females. Males do not Quack. Just like guys can't give birth.

Females will have a slight green tinge ontop of the head.