When Canon 400/2.8 meets APM-TMB 105/650

My freind's new Canon 400/2.8 just arrived. We went to Nam Sang Wai this morning. We arrived there at about 8:00am and there were lots of people shooting at the good positions already. The AF of 400/2.8 helped my friend to shoot lots of birds especially those were flying. My 105/650 can only shoot those are standing....