Thanks guys! It was taken at one of my favorite spots, Coyote Hills Regional Park, on the east shore of SF bay.
The 3D look is due to the compression of the 420mm effective length. Those hills are quite a ways behind the ducks. And while I would to take personal credit as a focusing expert, the sharpness is mainly due to the awesomeness of the 1D MkIV and 300mm 2.8 (with a 1.4tc). Also I was using a wimberly head on my tripod, and it is really good for tracking birds in flight.