I have found guidelines for enclosed runs but I am interested in building a coop for birds that are free ranging. How much space do they need? We don't really have any mammal predators (apart from our pet cats) but we have hawks. We are temperate zoned (winter at nights gets to maybe -2°C/28°F summer gets to 30°C/86°F). Also, how much roost space do you need per bird (roughly). I am thinking of making something that can accommodate 15-20 birds.