A streaked, earth-toned spinetail measuring 17–18 cm. Upperparts brown to brownish-gray with dense black streaking; narrow cream eyebrow and grayish face. Crown gray and finely streaked. Orange gular patch, sometimes small or diffuse. Chest brownish-gray with fine streaks and underparts tawny-rufous. Long, graduated tail with dark brown center and rufous-cinnamon outer feathers, very visible when fanned. Brown wings with rufous-cinnamon wingband. Brown legs, dark bill. Juvenile duller, with faint gular area and mottling on the chest. Regional variation in Argentina: • NOA: more rufous-brown above, heavier streaking; strong rufous tones on wings and tail. • Central Sierras: grayer and more contrasting, denser streaks; underparts slightly duller. In the NOA, it may coexist with the rare Streaked Thornbird (Asthenes maculicauda). The Serrano is larger, browner, with coarse dorsal streaks, orange throat patch and long tail with rufous tips. A. maculicauda is smaller, grayer, with fine and uniform streaking, rufous forehead, and a strong, clear whistled song.
Distribution and habitat: In Argentina it inhabits montane grasslands, rocky slopes and low shrublands between 1,900–4,000 m. NOA: Tucumán, Catamarca, La Rioja (lilloi). Central Sierras: Córdoba (sclateri), San Luis (brunnescens). Dry habitats with stiff grasses, rocks, crevices and scattered shrubs. Resident; may move downslope in winter or after snowfall.
Behavior: Highly terrestrial: moves through grasses and rocks with quick, low-running movements. Forages alone or in pairs, occasionally in mixed flocks. When alarmed, prefers running escape over flying. Often holds tail at an angle while moving. Voice is a rapid, ascending trill. Call notes are dry “tic-tic-tic” series. Sclateri usually sounds drier and faster, while lilloi is slightly harsher.
Diet: Mainly arthropods: beetles, larvae and small insects. Searches on the ground among hard grasses and rocks; occasionally jumps to catch insects in flight.
Breeding: Well-hidden globular nest between grass clumps or rocks, made of dry grasses, lichens and fibers; lateral entrance. Clutch of 2 white eggs.
Conservation status: Not considered threatened. May be affected by overgrazing or grassland degradation, but remains common in suitable habitats.
Authors of this compilation: Diego Carus and Maria Belén Dri – 06/12/2025