Straneck's tyrannulet
Straneck's tyrannulet ("Serpophaga griseicapilla"), also known as the monte tyrannulet and grey-crowned tyrannulet, is a small species of bird in the family Tyrannidae. It is found in woodland and open habitats with scatted bushes and trees in south-central South America, but the details are still unclear. It breeds in Argentina, but may also breed in Bolivia. In addition to these countries, it has been recorded as a non-breeding visitor in Paraguay, and possibly Brazil and Uruguay (it is unclear if it is a regular non-breeding visitor or only an accidental visitor to  the last two countries). Visually it closely resembles the white-crested tyrannulet, but its voice is distinctive and its tail shorter. Considerable taxonomic confusion has surrounded this species, which for a period mistakenly was referred to by the scientific name "Serpophaga griseiceps", a junior synonym of "Serpophaga munda". Consequently, the Straneck's tyrannulet only received its scientific name in 2007 despite having been known since the early 1990s.