The nominate subspecies' crown and upperparts are olive-brown, the throat deep buff, and the chest and belly ochraceous.

M. m. pallida is paler still, its throat is more cinnamon than buff, and the facial mask is a lighter black.

[7] The nominate subspecies of olive-crowned crescentchest is found in La Paz Department of western Bolivia.

The species generally inhabits dry scrub and grassy areas with small bushes, but M. m. pallida also frequents sawgrass in the Chaco Basin.

[7] In Argentina the olive-crowned crescentchest breeds from September to December; an active nest was found in October in central Bolivia.

Two nests of M. m. pallida were cups of vegetable fiber and palm leaves; they were hidden not far above the ground.