Juan Fernández Firecrown

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 11.5 to 12 cm (4.5 to 4.7 in) long and weigh about 10.9 g (0.38 oz). Females are about 10.5 cm (4.1 in) long and weigh about 6.8 g (0.24 oz). 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 a 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.

The nominate subspecies of Juan Fernández firecrown is found only on Isla Róbinson Crusoe in the Juan Fernández Islands of Chile. The putative extinct subspecies S. f. leyboldi is attributed to Alejandro Selkirk Island. The species inhabits forests, thickets, and gardens, favoring shady areas. In summer, males are frequently seen in the island's only town, San Juan Bautista, feeding on the flowers of trees in Sonchus subgenus Dendroseris which are endemic to the island chain, and many of which are themselves critically endangered species. All of the breeding records are at elevations between 120 and 660 m (390 and 2,200 ft).

The Juan Fernández firecrown forages for nectar at the flowers of native plants, especially Rhaphithamnus venustus and Sonchus brassicifolius. It may also feed on introduced Eucalyptus and Abutilon during autumn and winter when most of the native plants are not flowering. It feeds by clinging to the flowers, and favors shaded blossoms well above the ground. Both sexes defend foraging territories, with males holding the more productive sites. In addition to nectar, the species feeds on small insects taken in flight or gleaned from leaves.