Telephoto for D90 safari

I am travelling to Africa to shoot with my D90. I have a Nikkor 18-200 but would like a longer telephoto. I am looking at the 80-400mm f/4.5-5.6 AF VR but would value advice as to whether this is the best option. I am particularly interested in bird photography so would like a lens with fast focus to lock on the birds in flight.