Plain-breasted piculet endemic to South America on the eastern side of the Andes where it lives in the western part of the Amazon basin. The species is present in southern Colombia, eastern Ecuador, Peru and western Brazil at altitudes of up to . It is found in open parts of humid lowland forests, flooded forests, riverside corridors, swamps, thickets and groves, and logged areas with secondary growth and wooded pastures. It often occurs in areas of young "Cecropia" and "Mimosa" trees. The plain-breasted piculet is usually seen by itself or in pairs, but it will occasionally joins small flocks of birds of
Varzea piculet is unlikely to be confused with any other piculet because it is the only species in its range with dark underparts. The varzea piculet is endemic to Brazil in tropical South America where it has a rather limited range. It lives along the Amazon River in a wildlife corridor, in the forest called "várzea forest", a freshwater swamp forest. It ranges from the confluence of the Amazon River with the Rio Negro in a , variable-width corridor downstream for about to the confluence of the Trombetas River from the north. The confluence of the Tapajós River joins here from the