A member of the family Locustellidae, this species is notable for sexual size dimorphism, among the most pronounced in any bird.

[2] It is a moderate-sized bird of nondescript plumage; the female brownish above and paler below, the larger male a darker brown.

The brown songlark was described by Nicholas Aylward Vigors and Thomas Horsfield as Megalurus cruralis in 1827.

An alternative generic name Cinclorhamphus is derived from Greek words cinclus/κιγκλος "wagtail" and ramphos/ραμφος "beak"[5] and cruralis from the Latin root crur- "leg, shin".

[8] They are probably the most sexually dimorphic passerine in the world in size difference, as well as likely the largest species in the family Locustellidae.

[11] The brown songlark has a large range, between 1,000,000 and 10,000,000 km²; while population size has not been quantified the bird is reported to be common.

Males are highly polygynous and compete directly for mates, giving rise to the pronounced size differential.

Preferring open terrain, there is significant habitat homogeneity (sameness) and excellent visibility across brown songlark territories.

Particularly, in periods of low food availability, the greater nutrient reserves of female hatchlings may skew the sex-ratio toward "cheaper" daughters.