White-booted racket-tail

The white-booted racket-tail (Ocreatus underwoodii) is a species of hummingbird in the "brilliants", tribe Heliantheini in subfamily Lesbiinae. It is found in Colombia, Ecuador, and Venezuela.

All racket-tails have pronounced sexual dimorphism. Only the male has elongated outer rectrices (tail feathers). These tail feathers have bare shafts with long terminal oval flags. In all five subspecies of white-booted racket-tail those feathers are straight and do not cross; the flags slightly overlap. Both sexes of all have greenish upperparts without a glittering forehead, and all have white leg puffs. Males have a greenish gray throat and a solid green belly. Male white-booted racket-tails are 11 to 15 cm (4.3 to 5.9 in) long including the 7 to 8 cm (2.8 to 3.1 in) long outer tail feathers, and weigh 2.5 to 2.7 g (0.088 to 0.095 oz). Females are 7.6 to 9 cm (3.0 to 3.5 in) long and weigh 2.6 to 3.2 g (0.092 to 0.11 oz).

The subspecies of male white-booted racket-tails differ in the color and shape of the tail flags; females differ in the pattern of green spots on their white throat and belly. These differences are:

O. u. polystictus (male) bluish black oval flags, (female) heavily spotted

O. u. discifer (male) bluish to turquoise-black oval flags, (female) medium density of fine spots

O. u. underwoodii (male) bluish to turquoise-black oval flags, (female) medium spotted

O. u. incommodus (male) bluish black oval flags, (female) medium to scarcely spotted

O. u. melanantherus (male) bluish black oval to round flags, (female) unspotted