Not sure if someone answered your question already about how to tell cockerel (I think they aren't technically roosters until they are a year old) or pullet (again, if I'm not mistaken, they are hens after a year old). You are correct that tail feathers, at that age, are a very helpful indicator. They start to get longer and might curve a bit, depending on breed. They tend to have more colorful characteristics as well. Also, cockerels tend to have a colored band over their shoulders, whereas pullets tend to have a relatively uniform body section (I am speaking in general terms here, there can be exceptions from what I've learned). Also, hackle and sickle feathers are a helpful indicator. You can see, in your photos, that the cockerels have a shawl of pointy feathers coming down and off their necks, versus rounded feathers you would see on a pullet. Those are called hackles, I think (I always get this mixed up). Then, right at the base of their tail, there is a similar swath of pointy feathers shaped like the hackles - those are sickle feathers (I hope I am getting this right and not backwards - people out there, correct me if I'm wrong!). At this age, all of these things are good indicators.
Redder combs and bigger waddles are sometimes good indicators, as are bright yellow, thicker legs compared to more muted, thinner legs, but I would caution against making any firm judgments based on these traits, they aren't always totally reliable. If anyone reading this finds mistakes in my summary above, please correct me so we're all getting good info.
Keep reading posts on here and you will learn tons! And congrats on the new chickens!
Redder combs and bigger waddles are sometimes good indicators, as are bright yellow, thicker legs compared to more muted, thinner legs, but I would caution against making any firm judgments based on these traits, they aren't always totally reliable. If anyone reading this finds mistakes in my summary above, please correct me so we're all getting good info.
Keep reading posts on here and you will learn tons! And congrats on the new chickens!