Genus Oreotrochilus: Andean Hillstars

Genus Oreotrochilus

The genus Oreotrochilus, commonly known as hillstars, consists of seven hummingbird species uniquely adapted to the high-altitude regions of the Andes.

Black-breasted Hillstar (Oreotrochilus melanogaster)

Endemic to Peru, this species is primarily found in the departments of Junín and Huancavelica, with some presence in Ancash, Lima, Pasco, and Ayacucho. It inhabits puna grasslands at elevations between 3,500 and 4,800 m.

The Black-breasted Hillstar is a year-round resident in Junín, but in Huancavelica, it might leave the puna after cacti stop flowering. It feeds on nectar primarily from Chuquiraga spinosa in Junín and favors cactus flowers in Huancavelica. It also feeds at other flowering plants, especially red ones, by trap-lining, and will feed at Eucalyptus. It hawks for insects on the wing.

The male's upperparts are bronzy brown, with a shining emerald green gorget, grayish brown flanks, and entirely black breast, belly, and vent area. The tail is slightly forked and blue-black.

Andean Hillstar (O. estella)

Found from Peru through Argentina, males display drab brown upperparts with a striking emerald-green gorget bordered by black, contrasting with a white breast and belly featuring a rufous central stripe. This species is known for using wool from llamas and alpacas to line its nest.

Until 2019, what is now the Green-headed Hillstar (O. stolzmanni) was considered a third subspecies of the Andean Hillstar. Similarly, the White-sided Hillstar (O. leucopleurus) was previously treated as a subspecies rather than a full species.

Ecuadorian Hillstar (O. chimborazo)

Native to Ecuador and extreme southern Colombia, this species inhabits mountain grasslands between 3,500 and 5,200 m. Males have a vibrant purple hood separated by a black stripe from the white belly and a dark line down the center of the belly.

There are two subspecies distinguishable by their throats:

• O. c. jamesonii: Entire throat is glittering violet purple.
• O. c. chimborazo: Violet-purple upper throat with a glittering aquamarine patch on its lower throat.

Nests are large for a hummingbird, built with warm materials like grass, moss, feathers, plant down, horse hair, and rabbit fur. In prime locations, several nests may be close together.

Blue-throated Hillstar (O. cyanolaemus)

Discovered in 2017 in southwestern Ecuador, the Blue-throated Hillstar is predominantly green with a bright blue throat patch that inspired its name. It has a velvety black collar around its throat, with white belly and breast, and a black longitudinal stripe down the belly.

Blue-throated Hillstars often face competition from Shining Sunbeams (Aglaeactis cupripenni), which frequently chase them away. Aggressive interactions also occur with the Viridian Metaltail (Metallura williami).

Wedge-tailed Hillstar (O. adela)

Found in Bolivia and Argentina, this species has gray-brown upperparts with a bronzy cast. The adult male features a glittering green gorget and chestnut underparts with a bold black stripe down the center. The tail is graduated and mostly blue-black, with cinnamon inner webs on all but the central feathers.

Initially assessed as Near Threatened by the IUCN, it was reclassified as Least Concern in 2021, with an estimated population of 2,500 to 10,000 mature individuals. While generally uncommon, it can persist in degraded areas if brushy ravines remain.

Green-headed Hillstar (O. stolzmanni)

Distributed across northern and central Peru and southern Ecuador, this species has a restricted range, making it vulnerable to environmental changes.

First described in 1895, the Green-headed Hillstar was traditionally considered a subspecies of the Andean Hillstar but has been recognized as a separate species since 2019 due to genetic and plumage differences.

Compared to the Andean Hillstar, males have a brighter green crown and a black (not brown) line along the central underparts. Genetic studies show a stronger mitochondrial DNA relationship with the Black-breasted Hillstar than with the Andean Hillstar.

White-sided Hillstar (O. leucopleurus)

Found in the Andes from Bolivia to Argentina, it inhabits puna grasslands with dwarf shrubs, cacti, and Puya. The species generally lives at elevations from 1,200 to 4,000 m (3,900 to 13,100 ft) but can occasionally be found higher, even near the snow line. It is visually very similar to the Andean Hillstar.

Color Variations

Among the seven hillstar species, five have green gorgets (Andean Hillstar, Wedge-tailed Hillstar, Green-headed, White-sided, and Black-breasted Hillstar), while the other two have blue or purple gorgets (Ecuadorian Hillstar and Blue-throated Hillstar).

Andean, Green-headed and White-sided are fairly similar. Black-breasted is distinguished by a black breast, and Wedge-tailed by rufous sides to the black breast. Blue-throated main distinction versus Andean is its intensely royal blue throat, and the Ecuadorian has an entirely and uniformly purple head and throat.

High-Altitude Adaptation

Hillstars are among the most specialized hummingbirds, capable of surviving at elevations of up to 5,200 m (17,000 ft).

To conserve energy, they enter a state of torpor at night, significantly slowing their metabolism. They also construct their nests in rock crevices or under overhangs, protecting them from extreme cold and harsh winds.

Birding at high altitudes presents unique challenges (read more about it here). However, exploring the Andean puna habitats offers a chance to see many remarkable bird species, including the Andean Hillstar, a resident of the Sacred Valley.

Sources

• IUCN Red List. (2024). Oreotrochilus cyanolaemus species assessment. Retrieved from www.iucnredlist.org
• Wikipedia
• eBird

Photo: Holmes Pantoja, Birds Hotel Molino, Birding Tours Peru