I have one rooster (accidental)...a Buff Orpington with 16 hens, one year old. He overbreeds them and they are all losing feathers, some have big bald spots.
Could you please post photos of the feather damage? We might see it as rooster damage or possibly as something else. Since it is all 16 of them overbreeding is an interesting term. Usually overbreeding is either with a very small flock or he has a very few favorites. With it being all 16 hens I'd think maybe the damage isn't that bad or something else is going in.
He's a beautiful bird and not aggressive unless I'm walking with food in my hand across the yard.
Could you expand on this? It's not acceptable for him to be human aggressive even if you have food in your hand. What does he do? If he is attacking humans he needs to go.
I could keep him, but with so many hens he shouldn't be overbreeding from what I've read. I could separate him into a separate coop, but he'd be able to see and hear the hens...and with no other roosters, he'd be by himself.
It is harder on them to be alone but if the alternative is death it may be a reasonable option. He may settle down in his own area.
It sounds as if he is an accidental rooster, your original goals did not include a male. What are your plans for having a male now? How does he fit your current goals? Many people have girls-only flocks and are quite happy. Your life will be simpler if you get rid of him.
I'm also not sure exactly how I'd catch him without help.
As mentioned above, off of the roosts at night.
I'm also not sure how long he'd have to be separated to let the hens start to grow feathers again.
If the feather comes out cleanly they will be replaced fairly soon. If even a sliver of the shaft is left behind that feather will not be replaced until the next molt.
do roosters calm down? If I knew he was likely to calm down after hitting a certain age, that would help.
Once they hit a certain level of maturity the dynamics between the girls and boys change. Instead of fighting him or trying to run away the girls squat for the boy if they respect him. If the girls cooperate instead of try to get away he stops using brute force and wins them over by the force of his personality. The girls' attitude makes a big difference too, the girls are part of the process. Sometimes you have one or more girls that have a strong personality and do not want to be subservient to any male. The worst of these is when you have a girl with a strong personality and a wimp for a male.
I had one cockerel manage a peaceful takeover at five months with mature hens in the flock. Those hens were willing to let him take over. Most of my cockerels seem to be able to manage that pretty peacefully at around 7 months of age but that depends some on the personality of the head hen. I had one that waited until he was 11 months old before he even tried and the head hen did not accept him at all. It was two rough days of fighting before he took over. That was a combination of him being a wimp and her being strong. Once it settled they did become best of buddies but I was afraid he would have to kill her to get her to accept his dominance.
I can't tell you what to do. What is best for you will depend on your goals and desires, not mine. Good luck!