Kama Sutra Magpies

I saw the strangest sight on the lawn. I didn't know what to make of it at first, so I blinked and looked again. It appeared to be a magpie with its wings in a kind of pyramid shape, lying face down on the lawn. Then I noticed it had two heads. As I reached for my camera, the shape began to dissolve and the top half of a magpie sandwich flew away, revealing the female lying flat on her back beneath him. The odd shape of the wings had been caused by hers being tucked around his. I have never come across birds using the missionary position for mating before. Are they unique in the bird kingdom?