White-sided Hillstar

Andean hummingbird measuring 12.5 cm with marked sexual dimorphism: Male: Upperparts grayish-brown with a slight metallic green sheen. Small white postocular spot. Throat bright emerald green, bordered below by black. Underparts white with a broad bluish-black median band on the belly (broader and more bluish than in the Andean Hillstar). Tail mostly white; outer rectrices shorter, narrower, and curved inward, white only at the base; this gives a more rounded appearance than in the Hillstar. Female: Grayish-brown back. Whitish throat with fine spotting (more delicate than in the Hillstar). Underparts white with a slight grayish tinge. Tail white with a central dark band; the three outer rectrices show more overall white than in the Hillstar, with a uniform dark green bar. Outer rectrix narrow לאורך its entire length. Juvenile: Similar to the female. Very similar to the Andean Hillstar (O. estella), with which it may locally overlap in northwestern Argentina during winter. Male with a broader and more bluish ventral band (in Hillstar it is narrower and ochre-brown). Tail more rounded and with more extensive white pattern on the outer feathers. In females, separation is sometimes difficult or impossible in the field.

Geographic distribution: Southern Bolivia (mainly Tarija) southward along the Andes to south-central Chile and western and southern Argentina. In Argentina: Andes from Jujuy and Salta to Chubut, with scarce records in Santa Cruz; southern records more widespread than previously thought.

Habitat: Rocky and arid ravines with shrublands in the Puna, Prepuna, and southern Andes. Also slopes with cacti, puyas, and humid montane grasslands. Typical elevation between 1,200 and 4,000 m a.s.l. In winter it descends to pre-Andean valleys, even down to 500 m a.s.l. or lower.

Diet: Mainly nectar from high-Andean shrubs and cacti (Barnadesia, Berberis, Chuquiraga, Puya, Ligaria, among others). The diet is complemented with arthropods captured from vegetation or in flight.

Behavior: Generally solitary or in pairs; may gather in winter at sites with abundant flowering. Fast and relatively high flight; also flies low in Andean wetlands searching for hidden flowers. Territorial and aggressive with conspecifics. Frequently perches on rocks, shrubs, and exposed structures. Often clings to flowers and stems to feed rather than hovering for long periods (personal obs.). Call is a short, repeated “tsit”. During chases it emits rapid twittering similar to that of the Andean Hillstar. Nesting: Large cup-shaped nest attached to vertical rock faces or in protected cavities; also in abandoned structures. Clutch of 2 eggs.

Conservation status: Species not threatened at the national or international level. It is a common species in suitable habitats.


Author of this compilation: Diego Carús and María Belén Dri –– 04/06/2026