Puffins (Eriocnemis) are small hummingbirds with a straight black bill, bright green plumage, and large «puffs» of feathers on the shin; These tufts of legs are usually white, but are black in one species (Black Thigh Puffleg Eriocnemis derbyi). The Sapphire Vented Puffleg is a large Eriocnemis, and is mostly bright green, with violet or purplish undercoats. The nominated subspecies, in Colombia and Ecuador, also has a blue crown. The tail is blackish blue, relatively long and deeply forked. The Sapphire Vented Puffleg sexes are similar, but females are duller and the belly of females in southern populations is whitish.
Sapphire-vented Puffleg is larger than most other sympatric species of puffleg. In Colombia and Ecuador, the sapphire-vented Puffleg can be distinguished from the Glowing Puffleg (Eriocnemis vestita), Turquoise-throated Puffleg (Eriocnemis godini), and Coppery-bellied Puffleg (Eriocnemis cupreoventris) by their larger size, longer, forked tail and bill longer. Also, the male Glowing Puffleg has a blue throat, and the Coppery-bellied Puffleg has a copper-orange belly, not a green one. Golden-breasted Puffleg (Eriocnemis mosquera) has green (not purple) vents and undertail-coverts, and a golden-green breast. No very similar hummingbird species overlaps with the Sapphire Vented Puffleg in Peru.
The Sapphire Vented Puffleg resides in the Andes. There is only one specimen, reportedly taken in 1898 from Mérida, Venezuela (Schuchmann et al. 2001); this locality is very isolated from the closest locality where this puffin occurs regularly, in southwestern Colombia (Hilty and Brown 1986). The sapphire-vented Puffleg is also found in the Andes of Ecuador, with most localities on the west slope, and ‘on the slopes above the central and inter-Andean valleys; there are relatively few records of the «real east slope» in the Andes in Ecuador (Ridgely and Greenfield 2001a). There is an apparent gap in the distribution of the Sapphire Vented Puffleg between southern Ecuador and northern Peru in Amazonas, south of the Marañón River. This species is widely distributed in Peru from central Amazonas south to Puno (Schulenberg et al. 2010), although it is apparently not found in the well-studied Cordillera Carpish in Huánuco. However, sapphire-vented puffleg has not (yet?) Been reported in Bolivia (Hennessey et al. 2003).
The altitude distribution of the sapphire-vented Puffleg in Ecuador is 2700-3700 m (but mostly below 3400 m) (Ridgely and Greenfield 2001a), and in Peru it occurs at 2400-3500 m (Schulenberg et al. . 2010).
The sapphire-vented puffleg occupies humid montane forest, especially forest edge, elven forest, Polylepis moist forests, and dense moorland (Fjeldså and Krabbe 1990, Ridgely and Greenfield 2001a, Schulenberg et al. 2010).
The Sapphire Vented Puffleg is primarily nectarivorous. The documented flowering plants that are visited by this puffleg are Barnedesia, Embothrium, mistletoes, and large Bomarea and Siphocampylus (Fjeldså and Krabbe 1990). The Sapphire Vented Puffleg also feeds on small arthropods, as do most, if not all, species of hummingbirds (Remsen et al. 1983).