I think I have talked my husband into building me a smaller coop. I have a rooster that is more aggressive to the other roosters, so I wanted to make a smaller house for him and some of the ladies. How many would I need in the house so that they will be able to keep each other warm when winter comes? I live in mid-Michigan, so we can get mild winters, like the one we have last year, or it can get down right cold. I will make the house about the size of a dog house. Also, the existing house is 7 ft. wide by 10 ft. long where the chickens are at with a 2 ft. wide hallway. Will the remaining, say, 10 be able to stay warm? I have 13 chickens total and 6 are Bantams.