Female ducks only moult once a year to coincide with when they have (or would have) ducklings. By the time the young are ready to fly the mother will have a new set of feathers. Ducklings have their first set of feathers by 6-7 weeks old and these are called juvenile feathers. At this stage both sexes look similar. Very soon after this they start to moult again, getting proper coloured feathers
Male ducks change their look twice a year so you could say they have a summer and a winter wardrobe. During the mating season when they need to look their best to stand a chance with the lady ducks their plumage is colourful. After this season (at the end of the summer) they have what is called an eclipse moult when they replace their summer finery with subtle, more camouflaged winter plumage that looks similar to the female. This drab plumage stays until the beginning of the year when they have their nuptial moult, changing them once again into the smart duck every female duck desires. Throughout the year they will have kept the same wing feathers so they they can fly all year round and are less at risk to predators.