Distribution

Found from southern Mexico south through Guatemala, Honduras, Nicaragua, Costa Rica, and Panama to western Ecuador, Venezuela, Suriname, and the Guianas, then south to Brazil, Peru, and Bolivia. For ranges of subspecies, see Geographic Variation.

Reported as local in Mexico in the lowlands of Tabasco and northern Chiapas (e.g., Peterson and Chalif 1973), but no specimens known from Mexico, and so status there uncertain (Howell and Webb 1995). Possibly also occurs on the Pacific slope of Mexico in Chiapas (Howell and Webb 1995). Uncommon in Costa Rica (Garrigues 2007), being found mostly in the foothills of the Caribbean side or the humid mountains near the central plateau of the Pacific side (Slud 1964) at 100-1200 m and occasionally to 1500 m (Stiles and Skutch 1989); absent from the tropical dry forest (Slud 1964). Rare to locally uncommon in Panama, with most reports from the Caribbean slope and Darién, very few reports from the Canal Zone, and no reports from the eastern side of the Azuero Peninsula to western Panama province, except for Cerro Hoya in Los Santos (Ridgely and Gwynne 1989). Present on both sides of the Andes in Colombia except for the forest of the southern Chocó region (Haffer 1975), to 600 m, and once to 800 m (Hilty and Brown 1986). Uncommon throughout French Guiana (Tostain et al. 1992), especially in marshes such as along the Kew river (GEPOG 2003). In Peru, uncommon in lowlands of eastern Peru to rare in the foothills of the Andes (Schulenberg et al. 2007), usually to 500 m and rarely to 1800 m. Rare to uncommon in Ecuador, recorded mainly from Ríos Napo and Aguarico up to 1000m in the east and in the foothills south to Azuay from 500-1500 m in the west (Ridgely and Greenfield 2001). In Venezuela, 500-1800 m in the Sierra de Perijá and northern Cordilleras, then sea level to 500 m in the south (Hilty 2003). Common to fairly common in Ilanos, but uncommon to local elsewhere (Hilty 2003). Found in the northern Pantanal areas of Brazil and common to the Poconé region (Dubs 1992).

Endemic to the Neotropics.

Preferred habitat is forested streams, river sandbars, and forest pools (Stiles and Skutch 1989, Hilty 2003). Uses both swift, rocky streams (as in Costa Rica, or in Andean foothills) and slower moving, sand- or silt-bottomed streams.

Reported to be increasingly rare in Costa Rica (Stiles and Skutch 1989), French Guiana (Tostain et al. 1992), and Panama (Wetmore 1965).

Stiles and Skutch (1989) described the Sunbittern as one of four small families (trumpeters and seriemas of South America, Kagu of New Caledonia) that remain as part of an ancient radiation from the Southern Hemisphere, which was divided by continental drift. This theory is contradicted by recent molecular work, which places the Sunbittern and Kagu basal in the Gruiformes and the seriemas in their own order closer to the Passeriformes (Hackett et al. 2008).

Cracraft (2001) claimed that the divergence between Sunbittern and the Kagu  traces back to a gruiform radiation out of Gondwanaland. Fain and Houde (2004) believed the divergence to have occurred more recently, probably about 35 million years ago prior to the disappearance of tropical forests during the Oligocene. Ericson et al. (2006) used molecular dating to trace the sunbittern-kagu back to the Paleocene 60 million years ago, with divergence during the Oligocene.