Slender-tailed woodstar

The slender-tailed woodstar was at one time placed in genus Chaetocercus but was restored to genus Microstilbon by the mid 20th century.[5] The species is the only one in its genus and has no subspecies.[3]

The slender-tailed woodstar is 7 to 9 cm (2.8 to 3.5 in) long including its 3 cm (1.2 in) tail. Both sexes have a short, straight, black bill, bronzy green upperparts, and a thin white stripe behind the eye. Males have a reddish purple gorget that flares to the side as "moustache" tufts. The rest of the throat is white, the underparts pale grayish with green mottling on the sides, and the undertail coverts are pale cinnamon. The very narrow forked tail is black. Females have darker cheeks than the male. They do not have the colorful gorget; their underparts are cinnamon-buff. Their central tail feathers are green and the rest cinnamon with a black band near the end.[6]

The slender-tailed woodstar is found from Bolivia's Cochabamba and Santa Cruz departments south into Argentina's Jujuy, Salta, and Tucumán provinces. There is one historical record from the more northern La Paz, Bolivia area. It inhabits deciduous woodland, shrubby areas, thorn scrub, and densely vegetated ravines. In elevation it ranges between 1,100 and 2,600 m (3,600 and 8,500 ft).[6]

The IUCN has assessed the slender-tailed woodstar as being of Least Concern. Though its population size is unknown, it is believed to be stable.[1] It is considered fairly common, though hard to observe because it is so small and secretive. It is thought to accept human-made habitats to some extent. It is found in at least one protected area in Argentina.[6]