White-tailed shrike-tyrant
The white-tailed shrike-tyrant is a species of bird in the family Tyrannidae, the tyrant flycatchers. 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 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 and A. a. pollens.
Description
The white-tailed shrike-tyrant is 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. Their wings are mostly dark gray-brown with paler edges on the flight feathers. Their underwing coverts are cinnamon-buff. Their central tail feathers are dark gray-brown and the rest are white with small dark marks at their tips. Their throat is white with blackish streaks, their upper breast and sides gray-brown, and their lower breast, belly, and vent whitish with a buff tinge. Both sexes have a brown to dark brown iris, a thick hooked bill with a black maxilla and a yellowish mandible, and black legs and feet.Distribution and habitat
The white-tailed shrike-tyrant has a disjunct distribution. Subspecies A. a. pollens is the more northerly of the two. It is found intermittently in the Andes of Ecuador. The nominate subspecies is found in the Andes of Peru from Piura Department to Pasco Department and then from southern Cuzco Department south through western Bolivia into the eastern parts of northern Chile's Tarapacá and Antofagasta regions. A separate population of it is in northwestern Argentina's Tucumán Province and perhaps a bit beyond.The white-tailed shrike-tyrant inhabits a variety of high elevation open landscapes. These include temperate zone shrubby grasslands, páramo, puna grassland, and montane scrublands. It favors areas with shrubs, rocks and boulder, or rocky slopes and cliffs. It also occurs around isolated and abandoned human structures, in Polylepis woodlands, and in Ecuador in farmland with introduced Eucalyptus trees. In elevation it ranges between in Ecuador and between in Peru. It ranges between in Chile; it is known only above in Argentina and its elevational range in Bolivia is unknown.