BY THE 1940S,
North American hunters and developers had driven these birds to near extinction. Though they rebounded, changing weather threatens them anew. Cranes nest in Arctic wetlands, surrounded by natural moats. Persistent warmth shrivels these defenses, exposing chicks to predators. But intense storms can drown hatchlings. Annual migrations to Texas bring other challenges: Dry watering spots along the way force them to fly farther between rest stops.