A fish hawk and a heron, both female, risk everything for each other on the most dangerous journey of their lives. Migrating the Atlantic Flyway from Maine to the Bahamas, they encounter a hurricane, savage predators, deadly skyscrapers, and an unexpected blizzard. Happily, they enjoy glorious nights flying under the great bird constellations--Cygnus the Swan, Aquila the Eagle, and other "star sisters." Most important, each bird learns to step up for the one she cares about. The scientific background includes the latest research on how birds navigate using landmarks, constellations, wind currents, the sun's track, the earth's magnetic field, internal compasses, and even smell.