A murder of crows
Hearing a noisy commotion I looked out of the window and on an adjacent roof saw quite literally a murder of crows; they were savagely setting about killing one of their kind who eventually managed to limp off the edge and with damaged wings gain enough flight to glide down to the railway tracks below.
Before long, the wounded bird was set upon again and last seen on a short flight out of sight where what must be at least twenty others swooped down and noisily finished off what they had started.
Steve