When can I determine the sex of baby chicks?

[JSW99]

I have Buff Orpingtons, Plymouth Rocks, and Ameraucanas (3 of each) that are about 3 weeks old. I've noticed that some have a bigger comb than others. I was wondering if I got some roosters in my batch that are supossed to be all hens. Is it just plain too early to tell? Are they supposed to look like that? How can I tell the sex (besides vent sexing)?

 

[speckledhen]

Barred Rocks can be sexed at hatch, as soon as they are fluffy. Later, males are much lighter than females, with yellower legs and the combs and wattles are prominent and pink by 4-5 weeks old.


http://www.dominiquechicken.com/Sexing_Dominique_chicks.html

This link is good for Barred Rocks, Cuckoo Marans and Dominiques and has very good photos.