Black-throated Thistletail Asthenes harterti Scientific name definitions

Black-throated Thistletail is a range-restricted, secretive furnariid of the central Andes. It inhabits undergrowth in montane forest from 2900 to 3400 meters in elevation in western Bolivia. The species is rusty-brown above with a buffy supercilium, long, spiked tail and gray underparts with a small white chin and larger black throat patch. Black-throated Thistletail is similar in appearance to the Puna Thistletail but is more rufous with a bolder facial pattern than that species. It skulks around in dense vegetation near the ground and can be detected by its song, a high, thin, descending trill.

17–18 cm; 12–14 g. Typical thistletail. Nominate race has vague light brown supercilium behind eye, rufous-brown face; crown and upperparts, including wings and tail, dark rufescent brown, slightly redder on forecrown; tail long , strongly graduated, deeply forked, barbs reduced in density and length distally, appears ragged and pointed; chin greyish-white, throat  black with whitish shaft streaks, underparts brownish-grey, browner on flanks and undertail-coverts; iris light brown to brown; upper mandible blackish to dark grey, lower mandible grey to pinkish-grey with dark tip; tarsus and toes blue-grey to grey. Differs from very similar A. helleri in slightly paler upperparts, slightly duller underparts, browner face. Sexes alike. Juvenile undes­cribed. Race bejaranoi  is more ochra­ceous, particularly on auriculars  , malar region and neck side, paler and more ochraceous forehead, usually paler, less blackish loral area, paler grey underparts with ochraceous sides and flanks.

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Mostly arthropods. Of 19 stomachs examined, all contained arthropod remains and two also contained a few seeds 1–2 mm in diameter. Forages singly or in pairs, mostly in understorey, but in bushtops at forest edge; mean foraging height in La Paz was 1·4 m above ground and 1·9 m below top of canopy. Gleans arthropods from foliage, mainly upper surfaces of green leaves, and small branches, occasionally from mosses, grasses and rocks.

Song  a series of emphatic squeaky notes, accelerating and then slowing, descending slightly at end, lasts 1–1·5 seconds; rodent-like “pseea”  as alarm.