tree hugging is one of the behaviours about which I am most conflicted; on the one hand, I want the flock to live as naturally as possible, but on the other hand, I don't want them to be predated in the night or first thing in the morning. I don't worry about the weather when they're out, as it's never extreme enough here (and there, I imagine) to kill them, and if it makes their night out uncomfortable, then it discourages continuance of the behaviour, which is what I want. So I always worry if someone sleeps out, and it's always a relief to see them again the next day.