Chaco earthcreeper

The Chaco earthcreeper has at times been placed in genera Ochetorhynchus and Upucerthia but since the early 2000s has been placed in its current Tarphonomus.[4] It has at times been considered conspecific with the other member of Tarphonomus, the Bolivian earthcreeper (T. harterti). The two of them are sisters to the rusty-winged barbtail (Premnornis guttuliger), and these three are in turn sisters to the tuftedcheeks of genus Pseudocolaptes.[4][2]

The Chaco earthcreeper has three subspecies, the nominate T. c. certhoides (d'Orbigny & Lafresnaye, 1838), T. c. luscinia (Burmeister, 1860), and T. c. estebani (Wetmore & Peters, JL, 1949).[2]

The Chaco earthcreeper is about 16 cm (6.3 in) long and weighs 18 to 31 g (0.63 to 1.09 oz). It is a small earthcreeper with a long and very slightly decurved bill. The sexes' plumages are alike. Adults of the nominate subspecies have an indistinct orange-rufous supercilium on a mostly dark brown face. Their forehead is dull orange-rufous, their crown and back dull dark brown, and their rump and uppertail coverts somewhat rufescent brown. Their tail is generally dull brown with progressively more rufous from the central to the outermost feathers. Their wings are slightly more rufous brown than the back with rufous bases on the flight feathers. Their throat and cheeks are white. Their breast and belly are brown and their flanks and undertail coverts rufescent. Their iris is brown, their maxilla blackish to dark gray, their mandible slate gray to pinkish gray, and their legs and feet blackish to dark gray. Juveniles have an overall rufous tinge but their forehead is less rufous than adults'.[5]

Subspecies T. c. luscinia has grayer (less rufescent) upperparts, more rufous on the wings, and paler underparts than the nominate. T. c. estebani has a paler back, a duller breast and belly, and no rufescent tinge on the flanks compared to the nominate.[5]

Subspecies T. c. estebani of the Chaco earthcreeper is found in Santa Cruz Department in south central Bolivia, in northern Argentina, and in western Paraguay. T. c. luscinia is found in the western Argentina provinces of San Juan, La Rioja, Córdoba, Mendoza, and San Luis. The nominate T. c. certhoides is found in northeastern Argentina from Río Negro Province north to Formosa Province. It has also occurred once in Rio Grande do Sul, Brazil.[5][6]

Subspecies T. c. estebani and T. c. certhoides of the Chaco earthcreeper inhabit dense scrublands and deciduous woodland in the Chaco Basin, especially areas with terrestrial bromeliads. T. c. luscinia inhabits slopes with dense shrubs in the Andean foothills. In elevation the species occurs up to 1,800 m (5,900 ft).[5]

The IUCN has assessed the Chaco earthcreeper as being of Least Concern. It has a large range, and though its population size is not known it is believed to be stable. No immediate threats have been identified.[1] It is considered fairly common in most of its range and occurs in at least one protected area.[5]