Why do you want a rooster? The only reason you need a rooster is for fertile eggs. Everything else is just personal preference. Determining why you want a rooster might go a long way toward how you approach this.
Each chicken is an individual. They develop at different rates and wind up with different personalities. Cockerels normally develop faster than pullets. They hit adolescence with hormones raging. The pullets are just not there yet. They don’t know how to do their part. The mating act is not just about sex either, it’s about dominance. The one on bottom is accepting the dominance of the one on top, whether willingly or by force. It often gets really messy when you have a bunch of out-of-control adolescents in your flock. I find that having older mature chickens in the flock helps some, but it still usually gets really messy.
There are no magic numbers when it comes to hen-rooster ratio. That 10 to 1 that is so popular comes from a specific situation, the pen breeding system many hatcheries use where they may have 20 roosters in a pen with 200 hens. Hatcheries goals are to produce fertile eggs. They’ve found that 10 to 1 ratio works best to get fertile eggs in that specific system. It really doesn’t have anything to do with roosters fighting or hens being over-mated. In different situations, such as free range or one rooster with the flock, you generally don’t need that many roosters to ensure fertility. Pen breeding is a very specific method. It does make a very nice flock but there are plenty of flocks that work really well with much smaller or much higher ratios. Some of that is personality of the chickens and some is how they are managed and housed. I find practically everything related to behavior works better if they have more room. It sounds like yours might be kind of tight so behavior problems tend to get magnified. I don’t know what magic numbers you are using to determine you can add one more hen, but you might follow the link in my signature to get some of my thoughts on space. A flock with a rooster needs more space than a flock of pure hens, especially if the hens are at the same level of maturity.
Your cockerel seems to be doing at least one thing right. He is trying to mate the one that is laying much more than the others. Many cockerels that age will be trying to mate the ones that are not laying too just to establish his dominance. There are signs the rooster can recognize that a hen is laying, the red comb being one. That’s who he should be mating. To me that is a good sign, but it is rough on that one pullet.
It should get a lot better when the others show signs of laying. His hormones should calm down a lot when he matures out of the adolescent phase. It doesn’t always work out that way but it usually does.
Until some of the others start to lay, is there some way you could isolate that cockerel from the pullets? He won’t like it and the pullets may not either, but it won’t hurt them to give hem and them a chance to mature a bit.
