Xantus's hummingbird (Basilinna xantusii) is a medium-sized hummingbird endemic to the Baja California Peninsula. It is 8–9 cm long, and weighs approximately 3-4 grams. Adults are colored predominantly green on their upper parts and back. The tail is mostly dark reddish-brown with faint black tips, but the inner two rectrices are green. The most prominent feature is the white eye stripe found in both males and females, and similar to the related White-eared Hummingbird. The stripe is further enhanced by a bolder black stripe that borders the lower side. Both genders share cinnamon-brown underparts including the undertail coverts, with the cinnamon covering the throat in the female, notably different to the contrasting white undertail coverts of the white-eared hummingbird. In the male the throat is an iridescent green, though it is often seen as black. The bill is reddish with a black tip and often slightly curved, unlike the often straight bill of the white-eared hummingbird. The crown is often slightly greenish, but it appears black at many angles.