Well typically but this isnt always true it depends on bthe breed, the males have pointed backish tail feathers and females have round. I think they are to young to tell that way but, i normally figure it out by looking at the bird as a whole. I look at the feather length, size of feat, if they have large spurs(females will have little button spurs), there comb size, wattles, the size of the bird compared to others of its age and type, how they interact with others like are they tall and proud watching over or are they just looking for food all the time. There are many ways to tell and you can nhever be sure, so dont get rid of them until your sure. How old are they.