Argentina (B), Bolivia (B), Brazil (B), Paraguay (B).
Eastern Bolivia (Santa Cruz), western Paraguay and southern Brazil (southern from Mato Grosso and Goiás) to southern Argentina (Mendoza and Río Negro); no definitive records from Uruguay, where probably occurs.
 
Population
Estimated population is 250 - 999 (2010) and decreasing.
Status EN
Habitat destruction through mechanised agriculture, intensive cattle-ranching, afforestation, invasive grasses, excessive use of pesticides and annual burning, and hunting are the main threats.
For more information see BirdLife International Species Factsheet.
Chaco Eagle (Buteogallus coronatus) [XC724905]
by Jacob Wijpkema from Cruzeiro da Fortaleza, Minas Gerais, Brazil (alarm call)
Chaco Eagle (Buteogallus coronatus) [XC62902]
by Robson Silva e Silva from South of San Pedro, Beni dept., Bolivia (call)
Subspecies
Closely related to Buteogallus. Sometimes considered to include Black Solitary Eagle (Buteogallus solitarius).
No subspecies.
Similar Species
Great Black Hawk (Buteogallus urubitinga) which lacks a crest, is smaller and shorter-winged. Adult blacker, immature more heavily streaked brown below.
References
See References.