NZ Lifestyle Block magazine poultry expert Sue Clarke replies: The new girls have obviously adapted well to sleeping in trees and will be acclimatised to the chilly weather so it will be hard to break them of the habit without drastic action.
First, ensure there is plenty of perching space away from the established flock, high up in the chook house. Even use a natural branch instead of flat wooden perches.
Make a habit of giving them a late afternoon scratch feed of grain in or near their house, then shut them inside for the night. A couple of weeks of doing this should see them get used to the idea. You can either open the door again once it is dark, so they can get out in the early morning, or just open it when you give them breakfast.
Alternatively, if there is enough room in your coop for them all to stay inside for a few days, shut them in altogether, especially if the weather is wet or cold. Make sure there is plenty of dry litter, like shavings or similar on the floor, for them to scratch around in, at least 10cm deep. Hang up an old cabbage/broccoli or silverbeet stalks, for them to peck at and scatter their pellets on the floor so they have to work to find it.
Then revert to letting them out during the day but ensure they are inside by about 4pm, before they think about going back to their old roosts in the trees.
If you can't make them change their minds, they should survive in the tree tops and at least they are safely out of the way of cats, dogs and rats!