I am not sure what kind of hawk that was but when I was hunting ducks a few years ago I saw a hawk flying around. There were about 10 ducks on the water about 100 yards away from me. The hawk started circling over them and then started swooping down at them. Whenever it got close enough the ducks would dive under water. He did this for about 5 minutes but never got one. So, I guess to answer your question I would say hawks do eat ducks if they can catch them.