Approximately 250 wild whooping cranes nest in northern Canada and winter in south Texas, flying 2,500 miles annually between these two distinct havens: the coastal marshes of the Gulf of Mexico and the boreal wilderness on the border of Alberta and the Northwest Territories. Through twists of good fortune, each of these terminal migratory places is protected from human encroachment by a U.S. national wildlife refuge on the one hand and a Canadian national park on the other. This last remaining natural flock of the species, its numbers small but slowly increasing, has thus become known by the...