I was given 4 mixed breed chicks that are reportedly 4 wks old. 3 are bantam and one is standard.... I think they might all be roos but don't want to post pics if it is too early. One of the bantams I am pretty sure is a roo because last week he started making this strangled I am wounded/dying noise every time he could hear the BR roo crow. So at what age can you really start being able to tell? Thanks!