White-bellied Woodstar (Chaetocercus mulsant)

Quick Facts

• Scientific Name: Chaetocercus mulsant
• Spanish Name: Colibrí de Mulsant
• Family: Trochilidae
• Known Nicknames: Mulsant's Woodstar
• Average Length: 7.5–8.5 cm (3.0–3.3 in)
• Average Weight: 3.8–4.0 g (0.13–0.14 oz)
• Wingspan: 9.5–11.0 cm (3.7–4.3 in)
• Key Feature: Glittering amethyst-purple gorget and deeply forked tail in males; white breast and belly in both sexes
• Primary Diet: Nectarivore (Nectar from flowering plants and small arthropods)
• Range: Andes of South America, including Colombia, Ecuador, Peru, and Bolivia
• Habitat: Humid montane forest edges, clearings, and high-altitude shrublands
• Social Structure: Solitary and highly territorial
• Nesting/Breeding: Small cup-shaped nests constructed from plant fibers and spider silk on thin branches
• Conservation Status: Least Concern (LC)
• Population Trend: Stable

The White-bellied Woodstar (*Chaetocercus mulsant*) is a diminutive marvel of the Andean highlands, distinguished as one of the smallest hummingbird species in the world. Often mistaken for a large bumblebee due to its minuscule size and slow, droning wingbeats, this avian gem is characterized by its signature snowy-white belly and conspicuous white flank patches that remain visible even during its unique, hovering flight. Males are particularly striking, sporting a brilliant, iridescent amethyst-purple throat and a short, deeply forked tail, while both sexes possess a short, straight bill perfectly adapted for sipping nectar from high-altitude blooms. Frequently observed perching atop the highest bare twigs of cloud forest edges, the White-bellied Woodstar combines a fragile, toy-like appearance with a hardy resilience, navigating the thin mountain air with a quiet, buzzing grace that sets it apart from its more aggressive hummingbird relatives.

Fun Facts

This diminutive hummingbird is frequently mistaken for a large bumblebee due to its tiny size and unique flight style, which utilizes slower, more audible wingbeats than its relatives. While hovering at flowers, it often performs a characteristic "tail-wagging" motion, pumping its short, stiff tail up and down in a rhythmic pulse. Males are particularly striking for their brilliant amethyst-colored throat patches, which they flash during territorial displays, yet they lack the typical aggressive nature of other hummingbirds, often preferring to "trap-line" along a set route of flowers rather than defending a specific patch. Additionally, their feet are so small and specialized for perching that they are virtually incapable of walking on the ground.

Habitats & Distribution

This species is distributed along the Andes Mountains in South America, spanning from Colombia and Ecuador through Peru to central Bolivia. It is primarily found in the subtropical and temperate zones, occupying both the eastern and western slopes of the mountain range across its geographical range. Its preferred habitats include humid montane forests, forest edges, and secondary growth areas. It is also commonly found in more open environments such as shrubby gardens, clearings, and agricultural landscapes. This woodstar typically resides at elevations between 1,500 and 2,800 meters, though it is occasionally recorded at altitudes as high as 3,500 meters.

Behaviours & Reproduction

Exhibiting a flight pattern that closely mimics large bees, this species often avoids the direct aggression of larger hummingbirds by blending into the environment as an insect. It is primarily solitary and highly territorial over nectar sources, frequently perching on high, exposed branches to survey its surroundings. Communication is largely limited to thin, high-pitched chips and the distinctive humming sound produced by its rapid wingbeats. The reproductive cycle is characterized by a polygynous mating system where males perform spectacular aerial diving displays to court potential mates. Following copulation, the male provides no parental investment, leaving the female to select a nesting site and construct a minute cup-shaped nest from plant down and spider webs. She independently incubates the typically two-egg clutch and assumes all responsibilities for feeding and protecting the young until they reach independence.

Diet

The White-bellied Woodstar primarily subsists on nectar sourced from a variety of flowering plants, particularly favoring the blossoms of trees like Erythrina and Inga, as well as various shrubs. To balance its high-sugar intake with necessary proteins, it actively hunts small insects and spiders, often capturing them in mid-air through hawking or gleaning them directly from vegetation. An especially fascinating aspect of its dietary behavior is its low-profile foraging strategy; due to its tiny size, it often flies with a slow, bee-like cadence, which allows it to sneak into the feeding territories of larger, more aggressive hummingbirds without being noticed. Additionally, rather than always defending a single patch of flowers, this species frequently utilizes a trap-lining method, where it follows a consistent, long-distance circuit to visit specific nectar sources throughout its Andean habitat.

Colors

The White-bellied Woodstar is a tiny hummingbird characterized by shimmering green upperparts and a brilliant iridescent magenta gorget in males. Distinctive white patches on the flanks and a pure white belly contrast with its dark, short tail, while females exhibit bronzy-green plumage with buffy underparts and a white stripe behind the eye. Their diminutive size and hovering flight act as behavioral camouflage, mimicking large bees to evade detection and competition from larger avian species.