I have four 7 week old chick's born from Americana roo and two black ee hens. I feather sexed them at a day old and thee days old. 3 were black and sexed as females with the two lengths of tips. One yellow fellow had slow growing feathers. Two of my girls are doing a little bumping and now I'm a little worried I have three boys. I've never sexed wrong yet with this method. Any ideas? We also had a chipmunk Wheaton from this hatch that passed at three weeks. Sexed by feathers as female also.