I went to Gigrin yesterday. I wanted to try out the various focusing options on the 5D Mark III, and I also didn't want to come home with same old same old, so I went in the middle hide (one of the higher ones) and used my 500mm with 1.4x on the tripod. I've usually shot hand held before from the bottom hides, using 400mm.
The light was bad and I needed a fast shutter speed so I set it to Shutter priority on 1/1600 and set the ISO to Auto. I'm really posting this to demonstrate the ISO/noise handling of this camera, as well as the focusing. This was taken at the massive ISO of 12800, yes that's not a typo, that's twelve thousand, eight hundred!!! There was a little bit of noise in the background that I smoothed over in Lightroom 4. Exif shows I also used PS CS4, that was to remove the wingtips of another bird in the frame, using the cloning tool.
More to follow from Gigrin, the buzzards were behaving very nervously, never seen them like that before.
Camera................Canon EOS 5D Mark III
Exposure.............0.001 sec (1/1600)
Focal Length......700 mm
Exposure Bias...+2/3 EV