Description wikipedia

The red-tailed comet (Sappho sparganurus) is a medium-sized hummingbird belonging to tribe Lesbiini of subfamily Lesbiinae, the "coquettes". It is found in Argentina and Bolivia and possibly Chile and Peru. Male red-tailed comets are 19 to 20 cm (7.5 to 7.9 in) long including their 7 to 10 cm (2.8 to 3.9 in) tail. Females are 12 to 14 cm (4.7 to 5.5 in) long. The species weighs about 4 to 6.5 g (0.14 to 0.23 oz). Adult males of the nominate subspecies have a shining green head with a golden green or emerald green gorget. Their back and rump are reddish purple and their underparts mostly green with buffy undertail coverts. Their tail is long and deeply forked. Its upper surface looks reddish purple to green depending on the angle of the light striking it. The tail feathers have a wide velvety black to dusky purple tip. Adult females are overall duller than males and have a shorter tail. Their head and back are shining green and their rump reddish purple. Their throat and underparts are pale buff with small green speckles on the throat, breast, and upper belly. Their outer tail feathers have white or buffy white outer webs. Juveniles are similar to adult females but have dull bronzy green upperparts with a slightly coppery rump and more white on their outer tail feathers. Subspecies S. s. sapho is paler than the nominate and is golden orange where the nominate is reddish purple. Both sexes of both subspecies have a reddish brown iris, a black bill, and black legs and feet.