It is a very showy hummingbird because of its long iridescent violet tail. This species is only found in South America. Its name Aglaiocercus means splendorous tail and derives from the Greek roots aglaia = splendor and kerkos = tail. Its epithet coelestis comes from Latin and means heavenly.
It has a short, pointed 20mm beak, weighs around 5.5g and measures 10.4cm.
Male is dark green above with iridescent green crown and small white eye spot. Its tail is very long and forked, metallic violet with bright blue tips and almost twice the length of its body with the outer rudder feathers longer than the others. It has an iridescent violet spot on the throat. Its rump and uppertail-coverts are blue in color and its dull coppery green belly with the under-tail-coverts buff green or green rufous. The female has a much shorter tail than that of the male, it is green above it with an iridescent blue crown and a bluish rump. It has a white throat dotted with green, a buffy white breast and cinnamon flanks. The young are similar to the female but with a green rump and a totally green ruff.
Very similar to the Long-tailed Sylph (Aglaiocercus kingi) but it has an emerald green or blue-green tail. The female is distinguished because she has an iridescent blue crown, not green in color and ventrally has a wide white stripe.
Two subspecies are recognized: A. c. coelestis that is present in Colombia, and A. c. aethereus in Ecuador.
This species is endemic to the Biogeographic Choco and is found from the headwaters of the San Juan River in Colombia to the southwest of Ecuador. In Colombia it is found on the western slope of the Western Cordillera from 300 to 2,100 m above sea level from the San Juan River to the south.
It is a common inhabitant in the humid jungle of the Pacific slope where it is commonly found on the edges. Males forage primarily in the sub-canopy and understory, while females primarily concentrate in the lower understory.
It feeds on the nectar of flowers, especially those with a short and tubular corolla. It is considered an important pollinator of epiphytes of the premontane pluvial forest such as some species of the genera Columnea, Clusia, Inga, Guzmania and Psammiisia.
Individuals in reproductive condition have been registered in the months of December and July. The young are more frequent between May and July. They build nests outside of the reproductive season to rest at night. Sunido is built with moss.
It is a solitary and territorial hummingbird. It establishes foraging routes and aggressively defends flowering shrubs such as those of some species of the genera Miconia and Palicourea. Sometimes it is observed in aggressive interactions with other hummingbirds such as Green-fronted Spear Beak, the Naguiblanco Hummingbird and the Inca Pardo. It hunts insects by hawking them on leaves or among grasses. At times it behaves like a nectar stealer using holes made by primary stealers.
The taxonomic limits of the genus have caused controversy. Some authors consider that all taxa represent different species, while others propose including them within the same species.
State of conservation
At the national and international level, it is classified as a species of least concern.