I know they can tell them apart but my rooster knew before he ever seen the girls. I had two buff roosters in a pen together and I bought three 3 from a breeder. Before I ever got the girls out of the carrying cage one of the Roos was trying to get out and get to em. Did ge know try were hens or was he just trying to check em out. I thought it was weird how fast he reacted to them and never saw em. Do hens have a smell like does do to bucks?