Eagle pics

There is an eagle aerie about 50 yards from a major roadway. The local police are ticketing people that try to park and take pics so I'm thinking about walking or bicycling to the spot.
I'll be taking the wifes 40D 100=400L 1.4 extender and a tripod. It looks like a full sun day and the sun will be behind me. Even with walking in, they might chase me away from the roadside.
What settings make sense for this shot? I might not have much time to fiddle around on the spot.

I use aperture priority. Set your iso to get a shutter speed above 1/500, the higher shutter speed the better. I would practice using exposure compensation to tweak in your exposure. For instance, if you're shooting a bird against a bright sky you will need 1 to 2 stops of EC to get the subject properly exposed.

If you have not shot with this lens and extender for a while I would also suggest some practice prior to getting to your shooting spot. I have a Sigma 50-500 and while I like the lens I don't need it all that often and when I do put it on my camera I have to start up the learning curve each time.