Mallards are 2 months old. I know the one with the white ring is definitely a male. That one also has a lot of green on its head. We are uncertain of the other one. It is feathering in just like the male; however has an orange bill and no white ring. Its back is getting darker and has less consistent patterning. The male actually has more female-looking pattern on its back. Neither one quacks either. Purchased them to hopefully have two females for egg laying, so if they are males I want to sell them soon so that I may purchase some hens. That is why I am trying to figure this out sooner, rather than just wait it out the next couple of months.