I would shot in front of them (bill end) and swing in the direction of the wind at their ground speed. The wind should take the shot into dinner. But how far depends on the wind speed, your load and their distance and altitude. We had some good wind recently and I enjoyed the eagles and other predator birds hovering motionless and stationary. Not sure why they didn't need to flap at all? I saw a group of ducks trying to migrate south into a strong wind and every time they got above a tall tree line it blew them back and they had to try again. 1 and then 2 more broke out eventually, but the rest of the 100+ never went anywhere for the hours I watched.