The White-tailed Emerald is a small hummingbird of Pacific-slope foothills from Costa Rica to western Panama. Males contrast green plumage with white, while females show a white throat.
The male has green upperparts, a white lower belly, and white outer tail feathers. The female is whitish from throat through breast; the bill is short and slightly decurved.
It visits flowers in foothill forest, forest edges, and gardens on the Pacific slope. It occurs at about 800–2,200 m.
An extinction-risk assessment has not been added yet.