I will try and answer a few bits as my mate has chickens but cant help with all sorry. All birds can smell well there droppings if not cleaned up enough. I think there is worming treatments for the birds that need doing, They tend to have a few feathers clipped but if kept in a large avairy i suppose you dont need to do this. Hens some times will only lay up to a certain age and one of my friends doesnt lay at all but the other 4 do. Personally i think its unfair to keep hens on there own they much prefere the company of others. They do a fab job of keeping down the weeds and also like slugs and snails but if your garden is very small can be churned up some what. My mate got hers from Longdown dairy farm in the new forest as babies. They were fantastic with any ques and also any advice for after care. Very tame bird and love to be picked up. P.S dont wear sandles they love your toes and it hurts.....