oh, sorry, forgot to answer. THey are the feathers right behind the wing but before the tail feathers. ROosters get long, pointed saddle feathers. IF you go to the home page of BYC then on the left side of the page they have the learning center button, click it and then go down to chicken anatomy, they have a pic of roos and hens. YOu can see the saddle feathers there.
I think they start to show somewhere aroun 16-20 weeks. I'm going to look for a pic to show you the difference. I didn't know until I started looking here too.