Every sunset or so these autumn days a Detroit cement contractor named Tom Nardoni (right, holding record player) spins a disc called Young and Nesting Crows. Lured by its far-out sound, a vast flock of crows rises from its rookery outside of Essex, Ont. and swarms rapturously toward the gun of Bill Scott. "Their curiosity kills them," chuckles Scott, a Detroit machinery dealer. "I've seen them come in so low they practically sat on the end of the gun barrel. Then bang! and you blow them to hell. But let one get away with his feathers singed and he'll tell his buddies and they won't come at all."