Chickens NEED aged bacteria from OLD hay with manure (cow/horse/chicken/pig) or old garden/leaves/compost that has been AGED and mixed with dirt/mulch in the new coops that you are making NOT (let me repeat this) N-O-T fresh clean hay or pine shavings. Its best to use the same coop litter that is aged and has "coop immunity" When buying pullets or hens - you should use aged compost to start off your coop and get it established
Here's why: Would you buy new pet fish, from a pet store, that has been swimming in established aged water balanced with bacteria and then take them home and put the new fish that you purchased into FRESH pure water like purified or distilled water?
Not a good idea because the fish would die from the sterile water. All animals need a proper place to live. Fish need OLD water with an established ecosystem AND SO DO CHICKENS!!!!! If you move chickens from a coop with established aged balanced compost into a new coop with sterile bedding this can shock the hens' system.
Its up to you to provide the BEST BEDDING with the proper PH balance and enough ventilation (air-flow) and importantly the right humidity for your chickens
Poultry manure specifically:
Poultry manure, which is a key component of poultry compost, tends to have a neutral to moderately alkaline pH, typically in the range of 6.5-8.0 Aged and older chicken compost will generate a "natural flock immunity" to help keep chickens system balanced