Barn Swallow flock

Just after sunset today I watched a flock of 10's of thousands of Barn Swallows gather over a large corn field, and then as darkness came down, so did they. Within about 15 minutes almost all of them had found a place to perch for the night on the leaves of the standing corn plants, but they did not quickly go to sleep. The loud combined chatter of their voices could be heard long after they had dropped out of sight. This photo includes only a small percentage of the birds that were in the flock. I also heard a few Violet-green Swallows flying with the Barns. (Click on the photo for an enlarged view.)