White-tailed Shrike-Tyrant

The white-tailed shrike-tyrant (Agriornis albicauda) is a species of bird in the family Tyrannidae. It is found in Argentina, Bolivia, Chile, Ecuador, and Peru. == Taxonomy and systematics == The white-tailed shrike-tyrant has a complicated taxonomic history. It was formally described in 1863 as Dasycephala albicauda. What later became its subspecies A. a. pollens had been described in 1860 as Agriornis andicoloa. Soon thereafter andicoloa was discovered to have been used for a subspecies of the grey-bellied shrike tyrant (A. micropterus) so by the principle of priority the new species was renamed A. pollens. That taxon and Dasycephala albicauda were combined in the early twentieth century and again by the principle of priority the species became the present Agriornis albicauda. The white-tailed shrike-tyrant has two subspecies, the nominate A. a. albicauda (Philippi & Landbeck, 1863) and A. a. pollens (Sclater, PL, 1869). == Description == The white-tailed shrike-tyrant is 25 to 28 cm (9.8 to 11 in) long. The sexes have the same plumage. The two subspecies are practically indistinguishable though A. a. pollens may be slightly larger than the nominate. Adults have a dark gray-brown crown, a narrow buff supercilium, and a streaked face. Their upperparts are dark gray-brown.…