I've got 5 birds, one roo...that we got from the science teacher from school...my son brought one home, out of the brooder, on April 30...so I put that at the 4th week, they were fully feathered & you could tell a roo from a hen, easily...(a week prior actually), & now, I am guessing that they're starting they're 8th week, or I could be a week late, & they're actually 9 weeks old...I just checked one of my red hens, & she's got earlobes growin', a waddle growin' & her comb is getting longer (not quite pronounced)...& the two hens I had originally, are getting FAT! (Roo is a hawg as well!)