1. If the light isn't changing much you can just use manual exposure mode for birds. Meter on some fixed object and dial up or down by as much as a stop if the bird is much lighter or darker than what you metered on.
Agreed. I used manual mode last time out and, aside from one or two slip-ups, had much better results.
2. The 400/5.6 is sharp wide open. Unless you're close enough to the bird that DOF becomes an issue that's the aperture you should shoot it at.
That was a miscalculation on my part this time. I was hoping that stopping down would be more forgiving of focus misses, but I think it only stole light and maybe added some diffusion.
3. If you're tracking the bird on a loose gimbal head you can go to a somewhat slower shutter speed than pure handholding, but this depends on lots of factors (like how smooth you are in tracking). I wasn't great at this, but could usually get away with ~1/200s with the 400/5.6. (handholding without a tripod I wasn't happy with results below about 1/1000).
I definitely need more practice with the gimbal head.
4. Don't be afraid to bump the ISO up. Yes noise is annoying, but it's a much more recoverable defect than motion blur or serious underexposure.
I find that higher ISOs on the 7D tend to be costly in terms of sharpness when doing major crops. Although that is more a symptom of distance than anything.
5. GET CLOSER. I know this isn't always possible, but nothing (not even focal length) compensates for being too far from your subject. All of my best bird shots are from less than 200 ft. - most from under 100 ft.
Exactly the issue here. The area where the eagles hang out is quite inaccessible, so I'm relegated to standing on the accessible part of the shoreline across the lake. I know the area where he likes to fish, too, but it is also quite inaccessible. Like many lakes formed by a dam across a river, this one has steep sides that go right down to the waterline. The area where I was standing is a man-made "beach" where there is a pumping station. Much of the rest of the lake has either the aforementioned steep sides or swamp around it. But as a general rule of birding, I agree. Closer is better.
Anyway, Dave (dcstep) is a much more competent bird photographer than I am these days and maybe he'll have some even better pointers.
Dave will chastise me for going to f8 or f11 on these shots, I'm sure.