The Green Thorntail has a tail with a unique shape, where the feathers are disjoint and look like an X. While generally the body of the male is glittering green, its head looks grayish unless seen from the perfect angle. In low light, the head may take on dark purple tones. Both male and female show a white band on the back. The female also has white on the cheeks and belly, interspersed by black markings which join in a stripe running through the center of the belly. These are very small hummingbirds with a flight pattern very much like a bee, being smooth and slow, instead of the very fast movements that larger hummingbirds display.