The green-bearded helmetcrest (Oxypogon guerinii) is a species of hummingbird in the "coquettes", tribe Lesbiini of subfamily Lesbiinae. It is endemic to Colombia. Taxonomy and systematics The green-bearded helmetcrest was formally described in 1840 by the French ornithologist Auguste Boissonneau from a specimen collected near Bogotá in central Colombia. This species is now placed in the genus Oxypogon that was introduced by the English ornithologist John Gould in 1848. The genus name combines the Ancient Greek oxy meaning ″sharp or pointed″ and pogon meaning beard. The species name was chosen to honour the French naturalist and collector Félix Guérin-Méneville. The species is monotypic: no subspecies are recognised. The green-bearded helmetcrest was formerly considered a species named bearded helmetcrest with four subspecies. In 2014 the South America Classification Committee (SACC) of the American Ornithological Society agreed to a proposal to split this species into four separate species based on plumage differences and morphometrics. Other taxonomies soon followed suit. The other species are the buffy helmetcrest (O. stuebelii) of the Cordillera Central, the blue-bearded helmetcrest (O. cyanolaemus) of the Sierra Nevada de Santa Marta, and the white-bearded helmetcrest (O. lindenii) of the Cordillera de Mérida in Venezuela. Description The green-bearded helmetcrest is long. Males weight about and females It has a short straight black bill. The adult male has a long white crest and a mostly dark brown to black face with a white "collar". Its upperparts are bronzy. It has a thin glittering green gorget with white edges that forms a "beard". The rest of the underparts are grayish bronzy. The tail is moderately long, forked, and coppery to bronzy green with much white on the outer feathers. The adult female is similar to the male but lacks the crest and beard, and its underparts are buffy white with some greenish mottling. Juveniles resemble the adult female; the male has a partial crest and beard. Distribution and habitat The green-bearded helmetcrest is found in Colombia's Eastern Andes as far south as Cundinamarca Department. It inhabits humid páramo, especially that with Espeletia vegetation. It also sometimes occurs at the edge of Polylepis woodlands. Females often occur in gorges while males tend to remain in more open landscapes. In elevation the species ranges between . Behavior Movement The green-bearded helmetcrest is found year-round in páramo but is suspected to move to high elevation forest in the dry season. Its close relative the white-bearded