I have heard of this before and I always thought Buzzards took rabbits, etc. Let's face it, if we were capable of surviving in the wild and our food source of berries, etc was decimated we would survive by adaptation and find something else to eat. Animals are no different. In the case of BOP, their territories are decreasing, therefore so is their food supply. They have to adapt. If they totally strip an area, they have to increase their range by attacking their neighbour, just like tribal warfare, or move to pastures new, but that will also involve fighting for the new territory. These adaptations, peregrines attacking at lofts Sparrowhawk fashion, etc are all signs that they are becoming more desperate. The predators are going to have to predate on weaker predators down the line.