Ok, my 4 chicks are at about 6 weeks old. The farmer I bought them from was fairly certain that they were all females but couldn't guarantee it. So this morning I took them from the brooder to the run to enjoy the day and the two biggest chicks started "fighting". They were standing up as high as they could bumping chests and attempting to peck at the back of the other's neck. Does that make them roosters? I'm hoping that it's because one of the chicks has been the dominant one for a long time but the other one has grown to be the biggest and she might not like being pushed around anymore now that she's the biggest of them all. At what age can I tell from just looking at them?