The Garden Emerald (Chlorostilbon assimilis) is a small hummingbird that is an endemic resident breeder in Panama and Costa Rica. This is a species of open habitats, including bushy savanna, clearings, cultivation and gardens. They frequently gather nectar from short tubular flowers that are more commonly visited by insects, and when foraging, they wag their tails up and down. It can be found in the Pacific lowlands and hills, locally up to an elevation of 1500 m.

Adult male dark metallic green above with very narrow line of paler glistening feathers on lores and adjacent to base of bill, bluish-green tail-coverts, blue-black tail, with central feathers glossed slightly bluish green, wings dusky faintly glossed purple and underparts brighter metallic green than above, occasionally with slight blue sheen and femoral tufts white; iris dark brown, bill black, legs fuscous-black. Males often perch at low levels along the forest edge where they sing steadily. During hostile interactions with other hummingbirds, males make short dives and vocalize with a dry sputter.

Female has upperparts bright metallic green to bronze-green, often with bluish-green uppertail-coverts, tail blue-black, with central rectrices often dull metallic green, two or three outer feathers tipped pale grey, wings like male, dusky lores and upper ear-coverts, postocular spot white or greyish white, and underparts pale grey; often has legs black.

References:

del Hoyo, J., N. Collar, G. M. Kirwan, and P. F. D. Boesman (2020). Garden Emerald (Chlorostilbon assimilis), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.gareme1.01

Stiles and Skutch, A Guide to the Birds of Costa Rica.