The black-chinned sparrow (Spizella atrogularis) is a small bird in the genus Spizella, in the New World sparrow family Passerellidae. It is found in the southwestern United States and throughout much of Mexico north of the Isthmus of Tehuantepec; most populations in the US migrate south after breeding while those in Mexico are . It is a slim, long-tailed bird, primarily gray with a reddish-brown back streaked with black, brown wings and tail, a pink beak, and brownish legs and feet. In the breeding season, the male shows black on his throat, chin, and the front of his face. Females, youngsters and nonbreeding males show little or no black in these areas. An unobtrusive bird, it spends much of its time foraging slowly along the ground, either alone or in small groups, sometimes mixing with other Spizella species. It is an omnivore, feeding primarily on seeds during the winter and insects during the summer. It builds a cup-shaped nest of grasses, rootlets, or plant fibers, into which the female lays 2–5 pale blue eggs. The female does most or all of the egg incubation, but both parents feed the hatched nestlings. The species was first described by Jean Louis Cabanis in 1851. Four subspecies have been identified: one breeds only in the US, one only in Mexico, and the other two breed in both countries. Most northern populations move south—primarily into Mexico—for the winter. Because of its apparently large population size and very large range, it is considered to be a species of least concern. However, increasing global temperatures could have a significantly negative impact on its numbers. Taxonomy German ornithologist Jean Louis Cabanis first described the black-chinned sparrow in 1851, using a specimen which is thought to have been collected near Mexico City. He called it Spinites atrogularis. Within the decade, most authorities had moved it to the genus Spizella, where it has remained since. It is one of six small New World sparrows in the genus, and is known to have hybridized with Brewer's sparrow, a congener. Mitochondrial DNA studies have shown that the field sparrow is its closest relative. There are four recognized subspecies: S. a. evura, first described by Elliott Coues in 1866, is found in the southwestern United States and northwestern Mexico (northern Sonora). Also known as the Arizona black-chinned sparrow, it has been considered a distinct species (Spizella evura) by some authors (Coues and