A Convention of Birds

I noticed that the robins are still hanging around and the sparrows and cardinals still visit the bird bath on our tiny patio. Yesterday we saw a hawk by the air and space museum and a lot of other birds out in droves on the rooflines of several buildings along the national mall. Today we walked toward union station and on the way home there was a lot of chattering going on - an unusually loud type of chattering. Before reaching the Hart Senate office building there was what seemed to be thousands of birds flying around everywhere. They were on rooftops and treetops and chowing down on a single bird feeder in front of a church yard. It almost seemed ridiculous to think that that was the drawing card to get all these feathered creatures so excited. We minded where we were standing because we didn't want to become unnecessarily soiled from what was above us! It must be a stop on some migration pattern that neither one of us knows about. And since the leaves have all but completely fallen off the hordes of birds were even more obvious. I'm not sure what it was all about.  Maybe it has something to do with an afternoon rain forecast that will turn fall to winter? But it lasted about 2-3 blocks and then stopped. If anyone knows what that bird convention was all about please let us in on it. Creatures do things for a reason - we just can't figure this one out.