What age can you sex guineas at

As soon as you  hear the 2 syllable "buck-wheat" call, usually anywhere between 5- 8 weeks (my Mom says they are saying "butt-crack", lol). Only the females make that call. Some start sooner some start later, but 5-6 weeks old is when I start grabbing the "buck-wheaters" and banding a leg so I know how many Hens I have

I hear the noise in the brooder but when I go to see who is making the noise they all look up at me and shut up so I can't tell which one it is. I think I have 2 right now but there could be more since I can't tell if it is the same ones or not.
Mine are 5 weeks old. I love all the noises they make. So sweet!

I'm late but I actually came in to say:  when they are 10 years old, you may have figured it out by then!

It's not that you can't look at a guinea that is buckwheating and say "Yup, that's a girl".  You can.  And you can identify lots of males later by wattle size and behavior.  But some aren't vocal, some have confusing wattle shapes, etc.  So you can make a positive ID of
- females that call
- males with the big curved wattles later
- couples that obviously pair off later
- males that chase each other later
but you may find yourself with a few alleged males that keep you wondering. 

If you sit with them as suggested when they are young, and band them as you hear them, you'll get them all, I bet.  But if you're not going to band you may find yourself scratching your head occasionally.

Have fun with it, a little mystery is good.

I've heard the females say "Come Back"....... lol. Kind of yelling at there babies to stop wondering off.

1 year probably.

I am hearing a very clear BuckWheat from two of my guineas now that they are 9 weeks.  but I have been hearing occasional BuckWheat for about five weeks now.

"butt-crack"  yup, that's what they are calling the boys 

Hey... what do you use for bands and what age...  I want to band the first eleven for sure.  Both for sexing and for differentiating between two groups.