E, southern and south-eastern Brazil (Maranhío east to Rio Grande do Norte, and south to Mato Grosso do Sul and northern Sío Paulo, also southern Rio Grande do Sul), eastern Bolivia (Cochabamba south to Tarija and Santa Cruz), northern Argentina (south to Mendoza, La Pampa and northern Buenos Aires), Paraguay (except south-east) and Uruguay.
Population
Estimated population is unknown (2010).
Sooty-fronted Spinetail (Synallaxis frontalis) [XC843176]
by JAYRSON ARAUJO DE OLIVEIRA from Luque, Central Department, Paraguay (song)
Sooty-fronted Spinetail (Synallaxis frontalis) [XC764621]
by Mateus Gon\u00e7alves Santos from Po\u00e7\u00f5es, State of Bahia, Brazil (song)
Subspecies
Considered by some authors to form a superspecies with Azara's Spinetail (Synallaxis azarae) and Apurimac Spinetail (Synallaxis courseni) on basis of plumage and vocal similarities. Proposed taxon Synallaxis poliophrys was based on a misidentified specimen of present species. Plumage varies clinally, being brightest in north-eastern and dullest in south-west. Traditionally recognized subspecies fuscipennis, described from Bolivia, almost certainly based on this subtle clinal variation, as none of its alleged characters (broader and greyer frontal band, duller back, brown inner webs of central rectrices) allows diagnosis of individual specimens, even when comparing extremes from foothills of Bolivian Andes with distant populations from north-eastern Argentina. Population of R Cotacajes, in Cochabamba (Bolivia), apparently represents an undescribed subspecies.
BirdLife International Species Factsheet