Fertile eggs aside, without a rooster you may find that one of the more dominant hens will take over the job of protecting the flock. This may not necessarily be the head hen. But this protector, will act the part of a rooster, in all ways including the crowing, though not as loud.
You may notice one that stays off to the side of the rest of the flock. If you watch her, she is watching for prey, she gives warning calls. She finds food and calls to the other hens. Don't feel sorry for her. She is doing the job as protector of the flock, someone in the flock has to protect it from predators, its instinct. She will also be the one to breakup fights, so it is usually a large hen. She will help the head hen keep her position if they like each other.
These things I noted with my flock of 23 before i got my rooster. I needed a rooster for fertile eggs and because we have a lot of hawks.
The dynamics of a flock of hens is always changing, that is what makes chicken keeping so interesting.