Argentina, Bolivia, Brazil, Chile (B), Colombia, Falkland Islands (Malvinas), French Guiana, Guyana, Panama, Paraguay, South Georgia and the South Sandwich Islands, Suriname, Uruguay (B), Venezuela.
Population
Estimated population is 25,000 - 100,000 (2010).
Buff-necked Ibis (Theristicus caudatus) [XC879278]
by Fernando Igor de Godoy from Fazenda Rio Negro, Rio Negro, Aquidauana, Mato Grosso do Sul, Brazil (call)
Buff-necked Ibis (Theristicus caudatus) [XC699652]
by Fernando Igor de Godoy from Fazenda San Francisco, Miranda, Mato Grosso do Sul, Brazil (dawn song)
Subspecies
Forms superspecies with Black-faced Ibis (Theristicus melanopis), which was formerly considered a subspecies of this species.
The following 2 subspecies are recognised:
caudatus (Boddaert, 1783) - Colombia and Venezuela to French Guiana, south to Mato Grosso, Brazil.
hyperorius Todd, 1948 - Eastern Bolivia to south-eastern Brazil, Paraguay, northern Argentina and Uruguay.