I had welsummer eggs from two different sources and the males have feathered a little differently in each batch. An old poultry breeder told me that the surefire way to sex them at hatching is (1) the eyestripes on the female go right back, but are shorter on the males and (2) the big strip that goes down the back has a break in it on the males, for where the 'golden cape' will later grow. In my first batch, the male had a black chest when he feathered at 4 weeks, but in the second the feathering looked very much the same on both sexes, but on closer inspection, the males (who had longer legs by then) had chest feathers with darker edges to them. However, if they were truly autosexing then someone would not have created the welbar chicken I suppose!