Habitat
Subtropical and tropical lowland dry and moist shrubland, dry and moist forest, swamp forest, urban areas, rural gardens. From sea-level - 2,800 m, occasionally to 3,120 m.
Argentina, Bolivia, Brazil, Colombia, Costa Rica, Ecuador, French Guiana, Guyana, Panama, Paraguay, Peru, Suriname, Trinidad and Tobago, Uruguay (B), Venezuela.
Population
Estimated population is unknown (2010).
Southern Beardless Tyrannulet (Camptostoma obsoletum) [XC602556]
by Peter de Rouw from Ayampe River Delta, Manab\u00ed, Ecuador (begging call, call)
Southern Beardless Tyrannulet (Camptostoma obsoletum) [XC706964]
by Kent Livezey from Taquaral de Goi\u00e1s, Taquaral de Goi\u00e1s, Goi\u00e1s, Brazil (call, song)
Subspecies
Forms a superspecies with C. imberbe; the two overlap slightly without intergrading in west-central Costa Rica. Numerous subspecies have been described, many of which weakly defined and intergrade broadly with neighbouring ones. Subspecies form five geographically and morphologically discrete groups, within which the various taxa could arguably be merged: Central American (flaviventre, orphnum, majus), northern South American (pusillum, caucae, napaeum), western South American (sclateri, maranonicum, griseum), western Amazonian (olivaceum) and central South American (bolivianum, cinerascens, nominate). Some of these groups possibly merit status of full species; this especially true of extreme western Amazonian olivaceum, which sharply bounded on all sides by much paler subspecies and, moreover, is believed to have distinctive vocalizations. Other described subspecies are venezuelae (northern Venezuela), considered indistinguishable from pusillum, and bogotense (upper Magdalena Valley, in Colombia), merged with caucae as it represents a barely discernible intergrade between that taxon and pusillum.
The following 13 subspecies are recognised:
flaviventre Sclater, PL & Salvin, 1865 - Pacific coast of Costa Rica and both coasts of Panama.
orphnum Wetmore, 1957 - Coiba I, off south-western Panama.
majus Griscom, 1932 - Pearl Is, off southern Panama.
pusillum (Cabanis & Heine, 1860) - Northern Colombia (Caribbean coast, Magdalena Valley south to Santander), northern Venezuela (east to Sucre, south to Táchira, Barinas, Apure, northern Amazonas and northern Bolívar) and Trinidad.
caucae Chapman, 1914 - Central Colombia (western slope of western Andes, Cauca Valley, upper Magdalena Valley).
napaeum (Ridgway, 1888) - Southern Venezuela (Amazonas, south-eastern Bolívar), the Guianas, eastern Peru, and northern Brazil (eastern Amazonas, Pará, Amapá).
sclateri (von Berlepsch & Taczanowski, 1884) - Western Ecuador and extreme north-western Peru (Tumbes, northern Piura).
maranonicum Carriker, 1933 - Northern Peru (extreme eastern Piura, and middle Marañón Valley in Amazonas, eastern Cajamarca and eastern Ancash).
griseum Carriker, 1933 - Arid Pacific coast and slopes of western Peru (Lambayeque south to Lima).
olivaceum (von Berlepsch, 1889) - South-eastern Colombia, eastern Ecuador, north-western Peru and western Brazil (western Amazonas).
bolivianum Zimmer, JT, 1941 - Central Bolivia (eastern La Paz, Cochabamba) and north-western Argentina (south to Tucuman).
cinerascens (zu Wied-Neuwied, 1831) - Eastern Brazil (Maranhío east to Ceará, south to central Mato Grosso and Espírito Santo) and eastern Bolivia (eastern Santa Cruz).
obsoletum (Temminck, 1824) - Southern Brazil (southern Mato Grosso east to Rio de Janeiro, south to Rio Grande do Sul) south to Paraguay, central and north-eastern Argentina (south to La Pampa and Entre Ríos) and Uruguay.
BirdLife International Species Factsheet