Hi, I am testing my new 70-200 F4 IS on a few birds and I even with the 1.6 crop of the 40D you need to crop. Luckily the lens is sharp. The upload process may soften things a little and the 94K file size doesn't allow much. I am however very impressed with this lens. The "IS" is something to experience.
1/125 sec at f / 7.1 ISO 200 (overcast and low cloud produced low light)