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
White-barred piculet and heavily degraded former forest. The white-barred piculet was first described in 1825 by the Dutch zoologist Coenraad Jacob Temminck. It was given the name "Picumnus cirratus", the specific name meaning "curly headed", "cirrus" being Latin for a ringlet or curl. Molecular studies show that it is the sister species to "P. temminckii" and also closely related to "P. dorbignyanus", and at different times these species have been treated as synonymous. Six subspecies are recognised; "P. c. confusus" found in southwestern Guyana, northern Brazil and French Guiana; the Marajo piculet, "P. c. macconnelli" found in the eastern Amazon region of