The Juan Fernández firecrown (Sephanoides fernandensis) is a critically endangered hummingbird in the "coquettes", tribe Lesbiini of subfamily Lesbiinae. It is endemic to Isla Róbinson Crusoe, one of the three-island Juan Fernández archipelago belonging to Chile.
Taxonomy and systematics
The Juan Fernández firecrown shares genus Sephanoides with the green-backed firecrown (S. sephaniodes). It has one existing subspecies, the nominate S. f. fernandensis. Most worldwide taxonomic systems attribute a second subspecies to it, the extinct S. f. leyboldi. They list it as having occurred on another island in the Juan Fernández group, Alejandro Selkirk Island (also called Más Afuera). However, at least one author questions the two-subspecies treatment and whether a firecrown ever inhabited Selkirk.
thumb|left|Adult female drawn from a millinery specimen
Description
The Juan Fernández firecrown is among the most radically sexually dimorphic hummingbirds. The male and female plumages are so different, and even the female has a male-like iridescent crown, that in the 19th century they were thought to be different species until a nest was discovered with one of each sex. Males are long and weigh about . Females are about long and weigh about . Both sexes have a straight black bill.
The male is almost entirely cinnamon-orange. Its forehead and crown are iridescent fiery reddish yellow and the wings dark coppery gray. The female's upperparts are bluish green with an iridescent bluish purple crown. Its underparts are pure white with black and green disks and the wings slaty green. The central tail feathers and the inner webs of the others are blue-green and the outer webs white.