A small to medium-sized passerine, this species measures between 17 and 18 centimeters in total length. It possesses a highly cryptic plumage, featuring a dorsal pattern heavily streaked with black, buff, and grey on a brown background, which provides excellent camouflage against dry grass. The underparts are mostly whitish-buff, with a diagnostic, though often hard to see, pale yellowish-orange patch on the throat. The tail is relatively long and pointed, with the outer feathers showing characteristic cinnamon-rufous inner webs that are visible when spread. Its bill is thin, straight, and dark brown, perfectly adapted for probing the ground.
Geographical distribution: This bird is endemic to the southern cone of South America, primarily inhabiting the humid and semi-arid Pampas. Its range spans central and eastern Argentina (provinces of Buenos Aires, southern Santa Fe, Entre Ríos, Córdoba, La Pampa, and northeastern Río Negro), extending into southern and western Uruguay, and very locally into the extreme south of Brazil in the state of Rio Grande do Sul.
Habitat: It is strictly restricted to temperate, wet grasslands and seasonally flooded marshy areas known as espartillares. It displays a strong preference for dense, tall grass formations dominated by the genera Spartina and Cortaderia. The species favors low-lying plains with high moisture content and accumulated leaf litter, entirely avoiding areas subjected to heavy livestock grazing or agricultural clearing where vegetation cover is sparse.
Feeding: Its diet is strictly insectivorous, consisting of a wide variety of terrestrial arthropods such as beetles, ants, lepidopteran larvae, spiders, and small flies. It searches for prey directly on damp or muddy soils and at the very base of grass tussocks, using its sharp bill to rummage through leaf litter and probe soil crevices.
Behavior: Extremely secretive, elusive, and terrestrial, this bird rarely performs sustained flights or perches in high, exposed places. Instead, it prefers to run quickly through dense grass stalks, mimicking the movements of a rodent. During the breeding season, males will sing from midway up the grass stalks, uttering a series of high-pitched, metallic trills that accelerate toward the end, a vocalization used to defend territory.
Nesting: The breeding cycle takes place during the austral spring and summer, spanning from October to February. It constructs a spherical, domed nest made of dry grass stems, plant fibers, and fine roots. This nest is expertly hidden deep inside thick grass clumps, placed very close to the damp ground or directly upon it. The clutch consists of 3 to 4 plain white eggs, which are incubated by both parents for a period of roughly two weeks.
Conservation status: It is currently classified as Near Threatened (NT) on the IUCN Red List. The primary threats facing this species are the severe loss, degradation, and fragmentation of its natural temperate grassland habitat due to intensive agriculture, cattle overgrazing, and urban development, which destroy the dense, tall grass layers essential for its survival.
Compilation and publication: EcoRegistros – 24/08/2026