What do you mean by "maturity"? They should be fully feathered out by 4 to 5 weeks. It varies by breed, but you may be able to tell sex by 5 to 6 weeks, but with some it will be much later. You may see evidence of roosters developing "adolescent fascinations with the other sex" by 10 to 12 weeks of age. It is possible for a pullet to start laying at 16 weeks, but not very likely. I had 23 pullets. One started laying at 18 weeks. Two more started at 20 weeks, then two more at 23 weeks. Most were laying by 27 weeks, but when they start depends on breed and the individual pullet. It is physically possible some roosters can perform their biologic functions at about 16 weeks, but they may need to mature a lot more before the pullets or hens accept them as willing partners.
