I have four chicks that are supposedly all female. My brother saw them last night and said he thinks two of them are male. He said because two of them have round butts and not feather sticking out the butt they are boys. I think its different because they are all different breeds. The two that have feather butts are barred rock and rhode island red. The two that have round butts are buff orpington and black sex link. Any idea?