South-eastern Bolivia and central Brazil (southern from Mato Grosso, southern Tocantins, Goiás, and western Minas Gerais), southern throughout Paraguay and Uruguay to north-eastern and central Argentina (south to Río Negro and north-eastern Chubut).
 
Population
Estimated population is unknown (2010).
Screaming Cowbird (Molothrus rufoaxillaris) [XC49316]
by Rosendo Fraga from Buenos Aires, Argentina (call)
Screaming Cowbird (Molothrus rufoaxillaris) [XC326048]
by Aves del NEA from Faz. Verde Mar, Ribas do Rio Pardo, Mato Grosso do Sul, Brazil (call)
Subspecies
Analyses of mitochondrial DNA indicate closest relationship with Giant Cowbird (Molothrus oryzivorus) and Bronzed Cowbird (Molothrus aeneus).