It is apparent from the comments that I have been getting, Snow Buntings have the reputation of being hard to photograph. Let me share my method. They will repeat this pattern every couple of minutes (for hours at a time)>
Observing a group of Buntings consistently in the area, I began putting out a bucket of corn every day (and yes some tree huggers and purists call this baiting). The corn was placed on the back side of a mound of snow where it is not in camera view. A convenient perch was placed in the center of the mound, and being the highest point, individual birds use it before going to the ground. I am shooting from my bird blind (Dodge Ram with the Hemmi) from a distance of about 20'. For the close-up up shots I use the 600 with 1.4 converter, and for the group flight shots use the 300 with 1.4 converter. The Buntings will feed for about 30-60 seconds, and then perform a mass exodus to a nearby tree (see image 1000). Easy to pick off with the camera.
When shooting from the vehicle (in cold weather) be carefull to keep the heater off. The warm air exiting the vehicle will cause a shimmer and make your photos appear to be out of focus.
So - no secret! Bucket of corn, comfortable vehicle and patience!!