Distribution in the Americas
The range of the Horned Screamer extends from Colombia and Ecuador to south central Brazil.
In Colombia, there is an isolated population in the upper Cauca valley, where it now is confined to the Lago de Sonso in Valle, and another isolated population in the middle Magdalena valley (Hilty and Brown 1986); it also occurs in the Maracaibo basin. There is another very isolated population in southwestern Ecuador, in the province of Guayas (Ridgely and Greenfield 2001).
East of the Andes the Horned Screamer occurs east to northeastern Brazil, north of the Amazon to Amapá (Novaes 1974) and south of the Amazon to western Ceará and Bahia (Sick 1993). To the south, it occurs south to Santa Cruz, Bolivia (Hennessey et al. 2003) and to Mato Grosso and Paraná, Brazil (Sick 1993). It also occurs at one site in Paraguay (Pérez and Colmán 1995, del Castillo and Clay 2004).
The elevational range typically is below 800 m (Parker et al. 1996), and often the elevational range is even more constricted, e.g. below 300 m in Venezuela (Hilty 2003) and in Ecuador (Ridgely and Greenfield 2001). Locally the Horned Screamer occurs higher, up to 1000 m (Colombia, Hilty and Brown 1986) or to 1400 m in Peru (Schulenberg et al. 2001).
Distribution outside the Americas
This bird is not found outside of South America.
Horned Screamers are found in freshwater lagoons, tropical wet savannas, and lakes in open or forested zones (Hilty and Brown 1986, Hilty 2003, Kear 2005). It is common along the banks of rivers (Parker 1982).
The Horned Screamer has a wide distribution and is common in many areas, but the range of this species also has contracted significantly in some regions. The screamer formerly occurred on Trinidad, but was "verging on extinction" there by the 1930s," and has not been reported from there since 1964 (Herklotts 1961, ffrench 1985). It also is extirpated from all of the Guianan countries, with no records in Guyana since 1909 (Snyder 1966, Braun et al. 2007) or from Suriname since 1966 (Ottema et al. 2009). The type locality of the Horned Screamer is "Cayenne," suggesting that the species formerly occurred in French Guiana, but there are no recent records from that country either (Tostain et al. 1992).
The distribution of the Horned Screamer in western Ecuador also has contracted, although the size of the remaining population there now is increasing (Ridgely and Greenfield 2001).
Remains of the Horned Screamer that predate Spanish conquest have been found in Venezuela (Wetmore 1935).