Organized Birds

     So after arriving home from work this afternoon, I let the dog out, and followed her out the back door to my yard.  It was cloudy and cool and as I sat in the lawn chair and breathed in the fresh air, I tried to let the day's activities fade into the atmosphere above me.  I became aware of an increasing noise of bird chirps and calls - and I realized that the two trees in my neighbor's yard had filled with roosting cawing birds.  It seemed like hundreds of them were perched among the branches and as the throng noisily settled among the leaves, I wondered if could be as many as a thousand. 
     All at once it was quiet.  The entire flock suddenly and without warning took flight, swooping, gliding, and making a flowing black river in the sky.  I wished I had a video camera to record the patterns - and then, they were gone.  How did they all decide to suddenly fly, and what precipitated their departure?  They headed west - and were out of sight. 
     Nature simultaneously baffles and amazes me.  These birds with brains the size of walnuts somehow instinctually have a plan and excute it flawlessly.  Is there one leader for these thousands of birds who makes this decision, or do they just somehow know what to do and can do it together?  I wish we humans were as coordinated, with a singular plan and purpose.  Just think of what we could accomplish.