Nice silhouettes, Park!
Riverrunner: You are on the right path. I love the 70-200 f4, and swear I can recognize the wonderful color and pop of that lens.
My custom setting: C1 on my 7D is 1/1000s, f5.6 (max for my 400mm), and iso 400. If I can kick up the shutter speed in good light, I do it with the control wheel right by the shutter button.
Your 50D has options for C1 and C2. Just figure out your best wildlife/birding settings and set them up, then use the menu to 'register the settings'. Voila! A quick twist of the knob and you are dialed in. I find this to be pretty handy when an opportunity presents itself and I have a short amount of time to react.