The species has three subspecies, the nominate T. f. fusciceps (Sclater, PL, 1889), T. f. dimorpha (Bond, J & Meyer de Schauensee, 1941), and T. f. obidensis (Todd, 1925).

[2] Because the subspecies are different sizes and are geographically much separated, some authors speculate that they should be treated as full species.

[3][4][5] The nominate subspecies of the plain softtail is found in northern Bolivia in the departments of Beni, La Paz, and Cochabamba.

[3] The plain softtail inhabits tropical evergreen and river-edge forest, primarily várzea and the transition zone between it and dryer landscapes.

It tends to favor forest edges and areas with dense vine tangles.

It usually forages in pairs or small groups, often as part of a mixed-species feeding flock.

[3][4][5] The plain softtail's nest is a globe of twigs and soft plant material with two entrance tubes low on the side, placed in a branch fork in the canopy.

It has a large though disjunct range and an unknown population size; the latter is believed to be stable.