The white-throated mountaingem (Lampornis castaneoventris) is a hummingbird which breeds in the mountains of western Panama. It is replaced in southern Costa Rica by a distinct subspecies, the gray-tailed mountaingem, L. castaneoventris cinereicauda, which is very close to becoming a distinct species (García-Moreno et al., 2006). Another very close relative, the purple-throated mountaingem, is found sympatrically.
This bird is 10.5 cm long. The shortish black bill is slightly curved.
The adult male has bronze-green upperparts and underparts except for a brilliant green crown, white throat and blue tail. The female lacks the bright crown and throat, and has rich cinnamon underparts. Young birds resemble the female but have buff fringes to the upperparts plumage.
The female white-throated mountaingem is entirely responsible for nest building and incubation. She lays two white eggs in a deep plant-fibre cup nest m high in a scrub, small tree or vine. Incubation takes 15–19 days, and fledging another 20-26.
The food of this species is nectar, taken from a variety of small flowers, including epiphytic Ericaceae. Like other hummingbirds it also takes small insects as an essential source of protein. Male white-throated mountaingems defend flowers and scrubs in their feeding territories, and are dominant over most other hummingbirds. source