I won the Ducks Unlimted Photo contest last year with an even better one. In 3 years of entering I have placed in the top 10 4 times (several categories). I have taken some of the best pictures ever this spring. Nothing like ducks at 10 feet that don't know you are there.
Shutter speed for this was 1/1000 of a second. Minimum speed for flight is about 1/1250. For good regular flying birds I try to use at least 1/1600 second. Granted if they are coming towards you or going away 1/1000 will work. If you want to freeze the motion of the wingtips then you need to get upwards of 1/3200 second but then that looks rather uninteresting.
Wow, that's incredible! If I was taking that picture my focus would have been on the water and would have turned out terrible. My photographer skills are so poor, my best pictures come from my trail cameras :D