My little BR hen, Sophie, just started laying yesterday, and today I got to watch her while she was doing it. When she was finished laying (I was surprised, because it only took her about 15 minutes), she got out of the nest and starting grabbing straw and depositing it on her back. She did this for quite a while, and I've never heard of this behaviour before. Do they all do it? Perhaps this is some leftover "nesting behaviour"?