Anyone who has ever watched birds flocking will understand where Daphne du Maurier got the idea for ‘The Birds’ (or why Arthur Machen was inspired to write ‘The Terror’). There is something both hypnotic and intimidating about their aerial manoeuvres and tight-knit fellowships. They form tribes. And so often, people don’t. Quite regularly a parliament of rooks assembles in the trees behind my house at dusk. Often, hundreds of them show up. In the winter their evening get togethers are very noticeable on the stripped branches. They flap in like a raucous gang, settle on their perches, gossip about their day’s antics, and seem to eye us up as potential…