Black-thighed Puffleg Hummingbird Species

The Black-thighed Puffleg (Eriocnemis derbyi) is a medium-sized hummingbird native to the northern Andes mountains of South America. With its deep emerald green plumage, white leg puffs, and long decurved black bill, the Puffleg is a striking and unmistakable hummer.


The Black-thighed Puffleg is one of many species in the genus Eriocnemis, a group of mid-sized, high elevation hummingbirds restricted to the Andes. It is a member of the family Trochilidae, which includes all hummingbirds. There are over 330 described hummingbird species, making them the second largest family of birds behind tyrant flycatchers.

Hummingbirds are only found in the Western Hemisphere, with most species occurring in South America. They are specialized nectar feeders,capable of the fastest wing-beat of any bird which allows them to hover in mid-air. Their rapid metabolisms require that they feed almost constantly when awake.

Besides nectar, hummingbirds take small insects for essential proteins. Their unique adaptations allow them to occupy ecological niches unavailable to other birds. The Black-thighed Puffleg, like its relatives, is a vital pollinator of high Andean flowers and an important component of these fragile ecosystems.

Physical Description

The Black-thighed Puffleg is aptly named for the dense tufts of white feathers on the thighs of the male bird. The sexes are differently plumaged, with the female having white lateral tail feathers and more extensive white thigh puffs. She also lacks the male’s elongated outer tail feathers.

Adult males reach about 9-10 cm in length and females are slightly smaller at 8-9.5 cm. Weights range from 5-7 grams. The body plumage is primarily an iridescent golden-green on the back and rump, becoming more bronzy-green on the tail coverts.

The undertail is lustrous emerald. The crown and throat are an equal intense green. The black bill is long, decurved, and needle-thin for accessing nectar. The legs and feet are gray-black. Immature birds are less vibrantly colored until acquiring definitive adult plumage.

Distribution & Habitat

The Black-thighed Puffleg occupies a narrow elevational range between 2500-4000 meters in the Andes of Colombia, Ecuador, Peru, and Bolivia. Its fragmented populations are centered around habitats rich in flowers and feeding opportunities.

They are most abundant in humid montane forest and woodland edges with flowering shrubs and plants such as fuchsias and angel’s trumpets. They also occur in high elevation grasslands and scrublands. Range is localized and disjointed, with subspecies occupying different cordilleras.

The nominate E. d. derbyi is found in wet elfin woodlands of the Central and Western Cordilleras of Colombia. A Peruvian subspecies, E. d. atacamensis, inhabits dry scrublands of the Western Andean slopes. Various geographical isolates display subtle physical and behavioral differences.

Behavior and Ecology

The Black-thighed Puffleg, like most hummingbirds, is solitary and territorial. Males defend nectar-rich feeding territories from other males, and also mate with females entering their space. They display remarkable aerial agility and speed, with courtship involving flying in loops and dives to impress potential mates.

Their primary food source is nectar from colorful tubular flowers adapted to pollination by hummingbirds. Some favorite blossoms are in the genera Bomarea, Fuchsia, and Passiflora. The long bill and tongue allow access to calyxes of deep, fancy flowers.

As a critical pollinator, the Puffleg transfers pollen between plants strengthening genetic diversity. Insect prey including small bees, flies and spiders provide essential proteins. Foraging is done alone, with frequent aggressive encounters between territorial males.

Roosting occurs hidden in dense vegetation and low branches. The female alone builds a small cup nest on a low horizontal branch, using plant fibers and down. She lays 2 tiny white eggs over a period up to two weeks, incubating them for about 16-18 days. The chicks fledge in roughly 3 weeks, and reach sexual maturity at 1 year old. Predators include falcons and tyrant flycatchers.

Conservation Status

The IUCN Red List classifies the Black-thighed Puffleg as Endangered based on its small, declining population and habitat loss. Total world numbers are estimated between 1,000-2,500 mature individuals, but likely fewer remain.

Primary threats include habitat destruction, degradation and fragmentation from logging, development, agriculture and mining. Climate change impacts are also a concern, with drying conditions altering plant communities. Overgrazing by livestock reduces flowering vegetation needed for food.

Illegal collection for the pet trade and colliding with power lines take a further toll. Protected areas now preserve some key breeding sites. Continued protection of remnant cloud forest and scrub habitat is crucial for the survival of the fragile Puffleg populations. Ecotourism may offer an incentive for preservation.


The Black-thighed Puffleg is a unique high-flying pollinator exquisitely adapted to the Andean sky islands it inhabits. Its threatened status highlights the conservation challenges facing both animals and plants in this rich but delicate biome. Safeguarding remaining montane habitat is the key to securing the Puffleg’s future. Only through such efforts can we protect the vital connections between species upon which high Andean ecosystems depend.