Screaming Bloody Murder

When I came home this noon and went into the house I heard a bloodcurdling scream.  I thought maybe a rabbit had met it's demise.  Two minutes later I heard it again.  And again.  I kept on moving laundry and I heard it again.  This time I thought it was in the back yard.  Back upstairs I heard the scream again and I thought it was in the front yard.  I stuck some leftovers in the microwave and I heard the scream again but it sounded like the back yard.  Curious, I went out on the deck but could not see any animals suffering.  This would have to be a very large rabbit to scream this loudly.  Maybe one of the local feral cats had gotten injured. Or could a deer make this much noise?  Whatever it was had plenty of energy and of a pretty good size because it was still screaming.  Now I was really curious so I put my lunch aside, donned shoes, and went outside to explore and come to the bottom of this screaming.  As I reached the driveway I looked up.  Out of the tall dead tree flew a juvenile red shouldered hawk.  The hawk screamed again as it flew to the north.  This didn't sound like the typical red shouldered hawk that usually hangs around here.   Maybe this one is so young it doesn't know the whole red shouldered hawk song yet so it just imitates the sound of a rabbit dying very loudly.  I wonder for what evolutionary purpose the red shouldered hawks are so talkative?  Why scream bloody murder while resting in a tree?