Questions about putting chickens together

[the girls club]

I have 3 chickens that I'm about to move into the hen house with 6 other full grown chickens. They are large enough and old enough
My question is I found out I have a rooster amoung the 3. They are about 16 weeks old. I want to move them over because the weather is getting colder each night where I live. I know mother nature will take over and the fittest will survive. I know my 6 will attack them untill order is established
When I move the rooster over. At what age will he start to ferlilize the eggs as I don't want fertile eggs

 

[RanchGirl13]

once the chickens start to lay they usually relize that they are boys

 

[ChickenLegs13]

There's no set age. When you see him doing the deed then you'll know he's old enough, but then it will be too late and you'll have fertile eggs for a month. It will be soon too, so if you don't want fertile eggs keep him away from the hens.