Earlier this month, two beleaguered birds, the Great Green Macaw and the Military Macaw, gained the unfortunate distinction of being added to the U.S. endangered species list (the roster of species whose protection is mandated by the Endangered Species Act). But neither bird is a U.S. native. Instead, these spectacular parrots hail from parts of Mexico and Central and South America, where their populations are plummeting, primarily from habitat loss and the exotic-pet trade. Wild populations of the Great Green Macaw, for example, have dropped by more than 50 percent over the past 10 years. Since neither species resides in this country, U.S. laws can’t directly protect them from poachers and loggers. So what, exactly, does listing them under the Endangered Species Act do? Here’s some background on the ESA and how it can—and can't—help international species, including the two macaws. Has the ESA always protected foreign species? Yes. Since its inception, the act has...