Typical mating behavior between mature consenting adults
The rooster dances for a specific hen. He lowers one wing and sort of circles her. This signals his intent.
The hen squats. This gets her body onto the ground so the rooster’s weight goes into the ground through her entire body and not just her legs. That way she can support a much heavier rooster without hurting her joints.
The rooster hops on and grabs the back of her head. The head grab helps him get in the right position to hit the target and helps him to keep his balance, but its major purpose is to tell the hen to raise her tail out of the way to expose the target. A mating will not be successful if she does not raise her tail and expose the target. The head grab is necessary.
The rooster touches vents and hops off. This may be over in the blink of an eye or it may take a few seconds. But when this is over the rooster’s part is done.
The hen then stands up, fluffs up, and shakes. This fluffy shake gets the sperm into a special container inside the hen near where the egg starts its internal journey through her internal egg making factory.
You don't have consenting adults yet, you have a cockerel whose hormones are telling him to dominate the flock and immature pullets that don't have a clue what is going on. At that age mating is not about fertilizing eggs or sex. It is about dominance. The one on bottom is accepting the dominance of the one on top, either willingly or by force. When they are adults it is usually willingly but in adolescence it is usually by force. From what you describe it sounds really mild. Either the hormones haven't hit him hard yet or you have an unusually mellow cockerel. Sometimes these things go really smoothly and you wonder what all the warnings were about. Sometimes it is hard for the faint of heart to watch. From what you describe I'm not sure you are even this far yet.
The pecking is also about dominance. If one chicken runs away from another chicken when there is conflict, they have settled dominance. There will usually be a few repeated performances but as long as one runs life is good. The pullet that does not run has more spunk than the other two. You may see some skirmishes between her and the cockerel, it is possible these could become serious. But almost always between a cockerel and pullet, this involves more running away and chasing than actual fighting.
Good luck! So far it sounds mild.
