In 1974 a team of scientists trekking along the remote volcanic plateaus of southern Argentina made an unexpected discovery: a new species of grebe nesting on high-elevation lakes. In the short time since, the Hooded Grebe has become one of the most endangered birds in Patagonia. The divers breed exclusively on wind-battered lakes in the shadow of the Andes, where several factors are pushing them toward extinction. In summer Hooded Grebes build floating nests atop beds of red watermilfoil on lakes fed largely by snowmelt. Climate change has led to drier conditions in Patagonia, making bodies of water that are suitable for nesting harder to come by. In the 1980s scientists estimated that more than 100 lakes on Patagonian plateaus served as breeding colonies for at least 5,000 Hooded Grebes. Today there are only 20 lakes on which scientists can regularly find the 800 remaining individuals, says Kini Roesler, conservation director at Aves Argentinas. To help the species hang...