Saffron-billed Sparrow

The saffron-billed sparrow (Arremon flavirostris) is a species of bird in the family Passerellidae, the New World sparrows. It is found in Argentina, Bolivia, Brazil, and Paraguay. == Taxonomy and systematics == The saffron-billed sparrow has two subspecies, the nominate Arremon flavirostris flavirostris and the "gray-backed" A. f. polionotus. In January 2021, both the South American Classification Committee (SACC) of the American Ornithological Society (AOS) and the International Ornithological Congress (IOC) elevated the former subspecies A. f. dorbignii to species status as the moss-backed sparrow. == Description == The saffron-billed sparrow's name comes from its "striking orange bill". The adult male's head is mostly black, with a white supercilium from above the eye to the back of the head. The neck is gray and the back, wings, and tail are green. Its underside is white with grayish edges and a narrow black band across the upper chest. The adult female is similar but duller overall. The female's underparts are buffy with brown flanks. Juveniles are similar to the adults but duller. The species' length is from 15 to 16.5 cm (5.9 to 6.5 in). The mean weights of 27 specimens from three populations were from 23.6 to 28.1 g (0.83…