Most birds probably have the ability to rotate their necks 180 degrees.  Birds in general have long and very flexible necks, even though this is not obvious from the outside.  E.g., to see just how much neck there is, even in a bird like a pigeon, see the skeleton picture at the bottom of the page here (topic is also discussed in the text): http://sibley.enature.com/reference/reference_topic.asp?SectionID=3&TopicID=2 One advantage of this flexibility is that it allows them to preen almost any part of their body with their beak, which is critical given how important feather care is (without hands, all preening has to be done with the beak or the feet, and preening is often estimated to occupy 5-10% of a bird's day).  Flexibility probably has lots of other benefits, in terms of prey capture, predator avoidance, etc. etc. etc.  After a morning of warbler watching, I can certainly see the benefits ..... Chris Chris Elphick Storrs, CT elphick@sbcglobal.net