In South America, "alpine birds" are those bird species inhabiting the High Andes (>2500 masl). The study of this group has progressed from the inventories and catalogues of expeditions led by 19th-century European naturalists to ecological studies of their distribution, work which has enabled the production of country-specific field guides allowing for continued study by new generations of local researchers and amateurs alike. There are six predominant Andean ecosystems that alpine birds of South America inhabit: Paramo, Puna, high-Andean wetlands and water bodies, high-Andean forests, human-modified areas and glaciers. Here, we describe high-Andean bird diversity according to its distribution throughout these six ecosystems and discuss threats to bird populations and conservation approaches. Altogether, these habitats host a species-rich group of 945 species, composed of both resident and migratory species, generalists and also highly specialized, endemic birds. Because many are specialized, mountain-top species, adapted to live within narrow elevational ranges and climatic conditions, one of the greatest conservation concerns facing South American alpine birds is the threat posed by climate change. Although upslope migration appears to be a viable strategy for some species, there is also evidence that others, especially many endemic mountaintop species, could become locally extinct as a consequence of global change. The decoupling of species-habitat and other ecological relationships that could arise from altitudinal migration may be particularly serious for highly specialized birds of Paramos, Polylepis forests, and wetlands. Due to the high vulnerability of South American alpine birds to climate change, it is important to undertake actions for the conservation and restoration of the ecosystems on which they depend as habitat, ranging from legal protection to education.