Burst after burst of birds took wing, peeling from their nests to wheel and dip in terror. At first, their frenzied cries came as a high-pitched whisper. Then, as the fear spread, the screeching echoed and reechoed, building to a mindless surf of pain. In the crater’s dawn-warmed air, the scarlet motes hung in their millions, swirling and coalescing like drops of blood in free-fall.