And here’s a video of the nesting Blue Tits taken with the Canon 5D MkII the 100-400mm zoom lens and the 2x teleconverter.  Manual focus, ISO 100, program mode.  This video is an MP4 conversion and is only around 20Mb or so in size – the original HD video straight off the camera is around 2Gb and of much higher quality.  Seeing these little guys full screen and in tight focus on the monitor is pretty amazing.