I say pretty early to tell as I had pegged both my fcbm's for Roo's with the size of their Combs . One ended up getting really red w big wattles so he was def a roo . The pullet on the other hand took a while to be sure with the size ,color of her comb . I asked the breeder if this line was known for larger combs because visually it took longer to identify her sex .
Everyone assured me she was dude lolol she was not lol Sometimes they are tricky but I'm still learning Soo take that as you will lol