White-throated Mountain-gem

The grey-tailed mountaingem is about 12 cm (4.7 in) long and weighs about 5 to 6 g (0.18 to 0.21 oz). It has a medium-length straight black bill, dark cheeks, and a white stripe behind the eye. Males have mostly dark bronzy green upperparts with an emerald green crown and a black to bluish black tail. Their chin and throat are white, the sides of the neck and upper breast bright green, and the lower breast and vent area dark gray. Females have entirely bright green upperparts. Their central tail feathers are dark metallic to bronze green and the outer ones paler. Their throat and belly are dark rufous and the undertail coverts are gray with white or buff edges.

The white-throated mountaingem is found only in the mountains of western Panama's Chiriquí Province and south-central Costa Rica. It inhabits the interior, edges, and shrubby clearings of oak forest and also gardens in communities near the forest. In elevation it ranges from 1,500 m (4,900 ft) up to timberline.

The white-throated mountaingem feeds on nectar from a variety of flowering plants. Males typically feed at epiphytes in the forest interior while females more often feed in shrubby areas. Males are territorial, defending flower patches. They are dominant over smaller hummingbirds and subordinate to larger ones like the fiery-throated hummingbird (Panterpe insignis). The species also feeds on small arthropods gleaned from foliage.