For flying/moving birds/wildlife, I generally use M mode, 1/1600 s, f/6.3, Auto ISO, AI Servo with the center point selected with 8-pt expansion, and evaluative metering. For perched/static birds/wildlife, I use Av mode with Auto ISO and a minimum shutter speed of 1/500 s (I sometimes dial that back to 1/250 s in low light), One Shot with Spot AF, and spot metering.
Having said that, IIRC you are using a T1i/500D so several of those options aren't available to you. In particular, in M mode, Auto ISO will be fixed at 400 so that's not a good idea - you'd be better off with Tv mode, 1/1600 s and auto ISO, although that will mean your lens will often be wide open (I like f/6.3 or f/7.1 for a little more sharpness from the 100-400 and a bit more DoF).
Have a great trip!