I have seen that before Bill. They fly over my house almost every evening. Sometimes in no formation at all. They take off in the evening from somewhere down along lake Ontario about 15 miles north of me and head into the swamp 8 miles south of me for the night. When the big flights come in it has been estimated at between 20 and 30,000 on the ponds in the swamp. I think it is the Iriquois National Wildlife Reserve. Most of the people around her just call it the Alabama swamp.
bobg