Sexing Mallards

[EggHunter_66]

I am helping a friend hatch mallard ducks and we both are new to ducks and I was wondering roughly what age can you start seeing who's a male and who's a female? Also how is the best way to tell?
Thanks in advance for any help!!!

 

[The Moonshiner]

First thing I ever noticed was the males bills turning greenish.
Females stayed two tones brown.
Can't exactly remember at what age now. 5 weeks?

 

[EggHunter_66]

Thanks, that's a big help!!!