But then they flew north, according to this observer: https://ebird.org/checklist/S150568493.
Watched closely with several hundred new friends for over two hours.
They flew off at 5:12. They did not appear to have been flushed by any human activity.
They flew south for perhaps a mile, then turned out farther over the lake, and then turned back and flew north for a long time.
I lost them out over the lake, but they should be looked for to the north.