Systematics

Three to four subspecies are recognized for Saffron-billed Sparrow. One of the primary distinctions among the subspecies is in the color of the upperparts: green in the westernmost (dorbignyii) and easternmost (flavirostris) populations, and gray in the populations (polionotus and devillii) of the intervening region.

A. f. flavirostris occurs in central and eastern Brazil, from southeastern Mato Grosso east to southern Goías, Bahia, western Minas Gerais, and northern and central São Paulo (Hellmayr 1938, Jaramillo 2011). See Detailed Description.

A. f. dorbignii occurs in central and southern Bolivia (Cochabamba, western Santa Cruz, Chuquisca, and Tarija provinces) and northwestern Argentina (Jujuy and Salta provinces south to Catamarca) (Hellmayr 1938, Silva 1990, Jaramillo 2011). This subspecies is similar to nominate flavirostris but has a white supercilium extending anteriorly to the lores, and a narrower black pectoral band (Canevari and Acindar 1991, Hellmayr 1938, Jaramillo 2011). The olive back is duller than in flavirostris (Hellmayr 1938). This subspecies also has a gray median crown stripe in the adult male, which is more pronounced than in polionotus (Hellmayr 1938, Ridgely and Tudor 1989, Jaramillo 2011). Populations in Bolivia and Argentina appear similar (Hellmayr 1938).

A. f. devillii occurs in the interior of Brazil, extending from central Mato Grosso east to western Goiás and western São Paulo (Jaramillo 2011). It also is found in eastern Santa Cruz province, Bolivia (Jaramillo 2011). Subspecies devillii has gray upperparts, with olive limited to the wing coverts, which are greener than those of polionotus (Short 1975, Ridgely and Tudor 1989, Jaramillo 2011). The width of the pectoral band ranged from 3 to 7 mm in one sample, and 5 to 10 mm in another sample (Hellmayr 1938, Silva 1991). Silva (1991) considered devillii to be a junior synonym of polionotus.

A. f. polionotus occurs in northeastern Argentina in the provinces of Corrientes, Misiones, and the eastern parts of Formosa and Chaco. It is also found in Paraguay and in southeastern Brazil (western Paraná and southern Mato Grosso provinces; Hellmayr 1938, Silva 1990). Subspecies polionotus has gray upperparts and flight feathers, except for the olive yellow wing coverts typical of the species (Jaramillo 2011). The pectoral band width averages 8.2 ± 1.6 mm (Silva 1991). Subspecies polionotus has a faint gray median crown stripe (Jaramillo 2011).

Specimens of polionotus and dorbignii were found to vary from the northwest to southwest edges of their range in Argentina; the southern birds have a more brownish head and pectoral band, and duller underparts and shoulders (Nores and Cerana 1990).

Recent molecular phylogenetic analyses have shown Arremon flavirostris to form a clade with A. aurantiirostris (Orange-billed Sparrow) and A. taciturnus (Pectoral Sparrow) (DaCosta et al. 2009, Klicka et al. 2014).