Paul, certainly go ahead with the beer can test to reassure yourself you've got a good copy.
There are a host of potential issues here, any one of which could compromise IQ.
1. You're just not close enough to get good IQ on these. In some, the bird is underexposed, which opens it up to digital noise that becomes easy to see when cropped tightly. In all but No. 2, the bird takes up too small a portion of the frame for crops as tight as you originally posted. Simple answer is: Get closer.
2. I also recommend leaving your iso up at 400 until you've become experienced at BIF shots. Until you've really gotten the hang of it, the more shutter speed the better. Also, most copies of the 100-400L IS (I've shot four of them) are sharper stopped down to f8 than they are wide open. Stopping down and overexposing (overexposure using exposure compensationis a good idea for birds darker than the sky) will cost you two stops, another reason to bump iso to 400.
3. I extracted your exif data on shot No. 2, the most underexposed shot, and it said you used manual metering. I really don't recommend using manual until you're experienced at this type of photography. The image is at least a full stop underexposed (more likely two stops). Against a pale blue sky, simply selecting evaluative metering would have produced an osprey properly exposed. The whites would have been good, and the darks perhaps just a tad underexposed but not too badly.
4. I may have missed it, but which focus mode did you use? If you used one shot, it's quite possible the bird moved out of the focus plane between focus lock and tripping the shutter. And if it was al servo, it's possible, especially since most of these birds are so far away, that you were having trouble keeping the focus point on the bird. When shooting BIF, I generally select al servo and use the center focus point.
While high humidity can have an impact on IQ with supertelephoto focal lengths, these images don't look like that's the problem.
Good luck!
Steve - Thanks for the advice, I'll try what you have suggested.
1. So I need to be pretty close to these guys to get a clear, detailed shot. Gotcha.
2. Yeah, getting birds in flight is rather new to me, I just really started getting into trying to photograph the birds when my parents mentioned that they have Bald Eagles in this area, and I began to notice all of the Osprey, Herons, and other birds. It is quite addicting, but it is difficult. It's good to know that this is not something that is easy to pick up and requires some practice to get the hang of it.
3. So you're saying that I shouldn't shoot in M mode, and should try Av, set it to 8.0 and see what happens? I think that's my plan of attack.
4. I have the 20D set on AI Focus right now. I am using the center focus point. From what I gather on searching the forum, most people don't like AI Focus and I probably should be using AI Servo. Is that correct?
