|Courtesy Pandoozy Photos|
It's unusual to see crows congregating in such numbers; while they're very common, they're mostly solitary birds – unlike rooks or jackdaws, which form flocks. These had clearly come together for a common purpose, and it was chilling to see the efficiency with which they drove away the damaged bird. When it was over they melted away, and the street's Saturday morning silence seemed odd, like the returning hush after a firework display.
Birds of many species will expel or even kill individuals that are weak or diseased; it may be that doing so protects the health of the flock, or prevents it attracting the attention of predators. The target bird in this instance was missing feathers, which I might have put down to the moult had it not been so late in the year. Perhaps it was old, or in poor condition; perhaps the others couldn't risk having it around. Driving it away took energy; it was no passing skirmish but a prolonged attack. I'm sure they had their reasons, but it still felt chastening. We walked on to the common in silence.