Book excerpt: One winter, after an enforced period of quiet, William Fiennes finds himself restless and yearning for adventure. Inspired by his reading about the migratory patterns of birds, he flies to Texas to find the million-strong flocks of snow geese and to follow them on their spring flight thousands of miles north to breeding grounds on the Arctic tundra. This mesmerizing book, already a classic, captures their journey with wisdom, humility and endless curiosity. It is a meditation on freedom of movement, on seeing the world anew, and on the joy of returning - indefinably changed.