my male mallard is 14 weeks old tomorrow, he didn't start moulting into his big boy colors until about 2 weeks ago... so with that in mind if you have a drake he should be starting up soon.
I knew at about 2 weeks old for sure that my drake was indeed a drake as compaired to my duck his head was already shiney green (the dark black top of his head if you looked at it closely) and his back behind his wings was black and at around 8 weeks old this area started having an emerald green shine to it where as my ducks back behind her tail stayed tan and patterened... then the duck started quacking a lot at about 10 weeks and my drake started making his whisper quacks
This was my pair a few weeks ago:
^^The drake is the one at the bottom with the darker back^^
If you look close here you could see the emerald green shimmer on his back:
and here he is yesterday:
what's odd is I hear people say they get all this a 2 months old!?! I wish! They also say to look for the male curly tail thing at 2 months old, no way my drake that was the last thing he got when he moulted was that curly tail lol!
ETA: not to mention his bill was greenish for weeks
where as the ducks stayed that yellowish