Everyday at dusk, what is called a "Murder of Crows" would come in hoards and perch all over the area where I used to live. There were thousands of them and they did this as a ritual starting at 5:00 and ending at 7:00. Loud? Very reminiscent of Alfred Hitchcock's film "The Birds" . . . minus the seagulls. They even sat on top of the fake owls people would put on their rooftops to try and deter them.