The Screaming Sky - in pursuit of swiftsSwifts live in perpetual summer. They inhabit the earth like nothing else on the planet. They watched the continents shuffle to their present positions and the mammals evolve. They are not ours, though we like to claim them. They defer all our categories and present no passports as they surf the world's winds. They sleep in the air, their wings controlled by an alert half brain. Yet for all their adaptability and longevity swifts have recently been