Today's mystery bird for you to identify

Thee photographs of the same individual, taken yesterday afternoon through a pane of glass. Mystery bird (image 1) photographed at a bird feeder in Moscow city , Russia. Mystery bird (image 2) photographed at a bird feeder in Moscow city , Russia. Mystery bird (image 3) photographed at a bird feeder in Moscow city , Russia. Images: Mike Christie, 14:10 (Moscow time), 19 September 2010. [image 1, larger view ; image 2, larger view ; image 3, larger view ]. Note: All photographs taken through a pane of glass. Nikon D90 with Sigma 300mm macro lens. Mike writes: "It is the size and shape of a great tit but has the blue cap and bluish wings of a blue tit plus other markings from neither." I think we all can agree about which family and subfamily this bird belongs to and probably agree on its genus, but after that ... ? (I already emailed my guess to the photographer, who says he doesn't know what it is, but thinks my guess is only half-correct. Thus, we both are very interested to know what the hivemind thinks this bird may be.) If you have bird images, video or mp3 files that you'd like to share with a large and appreciate audience, feel free to email them to me for consideration.