I have had a lot of fun with these big birds this year. I probably shot 30 gigs worth this month alone, and "reconissance" before that. I have material to keep me busy for a long time. I get bored if I don't have something to work on in photoshop.
The eagle tree, has to be taken in early morning, or the sun is behind it, nothing but silhouettes. I had wanted an early morning shot of this. I am becoming more and more tuned into the golden light hours.

To answer your question, -I wanted depth of field. (f/13) to cover the varied distances of the birds and as much of the marsh as possible.(iso 400 is as far as I like to push it on these d series unless I have to) Which left me with 1/1250, ok since I was on a tripod with remote shutter release and static target.
I only use aperture priority or auto settings when I walk my dog and I only have one hand! 90% I use manual, I forced myself from the start. Of course, there are other choices. What would you have selected?

This was the same light, a little earlier. Since the plane of focus was flat, I was at f/6.3 1/400 and iso 100. That on the 20D and 500mm f/4. ( Also tripod mounted).