EF 600mm f/4 IS II
Juvenile kites are in particular attractive because of the golden speckles in the chest area as well as the rust patterns in the forehead, therefore I mostly concentrated on the younger birds. I had some opportunities with adult birds as well which I was able to take advantage of, thanks to the EF 600mm f/4L IS II.
The pixel level sharpness at 840mm f/5.6 is excellent and if not better, certainly in par with the EF 800mm f/5.6L IS. Click here for a 100% crop from RAW from the image above to examine the fine details.
While photographing kites, I had several encounters with the juvenile female northern harrier. Despite the somewhat challenging conditions given the distance and erratic flight pattern of the harrier, I was able to produce a frame that I liked from each flyby. In one of the encounters the servo tracked the harrier almost all the way down to the minimum focus distance (MFD) delivering surprisingly sharp results when the harrier was actually larger than the field of view at 840mm. Overall excellent servo tracking performance.
Light was quite low for the shot above (note ISO 3200) but the critical focus remained on the neck where the AF sensor was pointing. Needless to say, in better light tracking performance was superb despite the perfect pattern/color match between the harrier feathers and the background habitat which gives this raptor a unique, natural camouflage for hunting.