The SierraMadre sparrow was first discovered by scientists in the Sierra de Bolaños near Bolaños, Jalisco, in 1889. The eight specimens shot then were not recognized as what they were, but believed to be aberrant Savannah or Mexican Plateau song sparrows, or hybrids. Only when another bird was taken near the city of Durango in 1931 was it recognized as a valid and distinct species. The southern population was discovered only in 1945, but has been observed since then in several areas around Distrito Federal, Morelos, and Estado de México. Between 1951, when 5 were taken near El Salto, and 2004, when a small population was rediscovered in the same area, the northern population from Jalisco and Durango states was not found and believed to have disappeared. Meanwhile, the proposed subspeciesX. b. sierrae for the southern population was recognized to be based on individual variation and hence invalid; nonetheless, there is no gene flow between the populations and they constitute two separate ESUs. It is the sole species in the genusXenospiza; the genus is closely related to Ammodramus, differing mainly in the longer, less pointed tail, and restriction to high altitude alpine grassland habitats.
The species is endemic to some mountain ranges in and near the Sierra Madre Occidental, Mexico. It is restricted to bunchgrass and marshland habitat in volcanic mountain ranges, at altitudes of ; the lower part of the range is occupied by the northern, and the higher part by the southern population. Habitat information for the northern population is scant, with pine, oak, and Arbutus trees being mentioned. Better details are available for the more extensively studied southern population. The dominant bunchgrass species are Festuca amplissima, Peruvian feather grass, a muhly grass, and Muhlenbergia macroura. Small woods of Montezuma Pine and Lumholtz' Pine occur on elevated terrain.
Status and conservation
It is highly threatened due to clearance of its habitat for creating pastures. Its conservation status on the IUCN Red List is Endangered. This is because the species occurs in less than 5000 km², and its range, available habitat, and population size are shrinking. Despite the rediscovery of the northern population, no more than a handful of individuals are known to remain, and further research to locate additional subpopulations is urgently needed. In any case, the species will probably be uplisted to Critically Endangered soon; of the 4 subpopulations known, only one seems reasonably numerous.
