Thank you again, psweet. I do tend to remember my lesson's slightly better when I have to do some digging and look things up myself, rather than to just be given the answers (especially when it is a repeat, in less than a month... teachers (speaking of you, here) have so much more patience than I do... you never even said "Hey, dummy, you posted one just like this less than two weeks ago... can't you remember anything?".
When this group flew over, I said to myself "Gulls". There were about 5 different groups, and some looked a lot different, (dark in color, but not ducks), but I cant get pictures of birds in flight fast enough to actually see ANYTHING on, normally (today, I think I took about 40 pictures of birds in flight, and only in two of them can you tell there were actually birds in the picture, not just smears)
I am not quite sure how I went from "Gulls" by the river, to "Terns" when I got home, but I do believe that this bird is probably another Franklin's Gull, based on your tips.
Hmm can I guess? Franklin's gull?
You did post your answer before I came back to respond to psweet, but it looks as if we both came up with the same answer.