Canasteros and thistletails are small passerine birds of South America belonging to the genus Asthenes. The name "canastero" comes from Spanish and means "basket-maker", referring to the large, domed nests these species make of sticks or grass. They inhabit shrublands and grasslands in temperate climates from the lowlands to the highlands. They feed on insects and other invertebrates gleaned from the ground or the low vegetation.
The genus Asthenes was introduced in 1853 by the German naturalist Ludwig Reichenbach.[3] The name is from Ancient Greek asthenēs meaning "insignificant".[4] The type species was designated by George Robert Gray in 1855 as Synallaxis sordida Lesson.[5][6] This taxon is now considered to be a subspecies of the sharp-billed canastero (Asthenes pyrrholeuca sordida).[7]
In 2010, it was discovered that the thistletails and the Itatiaia spinetail, formerly placed in their own genera (Schizoeaca and Oreophylax, respectively), are actually part of a rapid radiation of long-tailed Asthenes.[2] At the same time, four species, the cactus, dusky-tailed, Steinbach's and Patagonian canasteros, were split off into the new genus Pseudasthenes.[2]
They are typically 15–18 centimetres (5.9–7.1 in) long and slim with long tails and thin, pointed bills. They are mostly dull and brown in colour but vary in tail pattern and presence of streaking. They have trilling songs.
Most species occur in open country, including mesic to arid scrublands and grasslands. Some species inhabit dry forests. Only three species are migratory.[8]