Every now and again, I come across a lone Magpie quietly chuntering away to itself. It can happen at any time of year and usually involves a single bird sat in dense cover, as if hiding. Why they do it I don't know. Being such a quiet "song", it can hardly be to attract a mate or declare a territory.
To be honest the next video shows a much more typical scene from a Magpie's day. It's titled "magpies and crow eating dead rabbit" and was filmed in a Portland quarry several years ago.