The coppery-headed emerald (Elvira cupreiceps) is a small hummingbird endemic to Costa Rica. It measures a mere 3 in (7.6 cm) in length, and weighs only 3 g (0.11 oz). The male has distinctive coppery crown and rump with a whole green belly and white vent. The female has a white belly and a narrow black subterminal band on white outer rectrices of the tail. Its noticeably decurved bill sets it apart from similar the allopatric white-tailed emerald.
This species is fairly common at middle elevations on Caribbean Slope, south to Reventazon River; from 600 to 1,500 m (2,000 to 4,900 ft). Also it is fairly common on Pacific slope of Guanacaste and Tilarán Cordilleras; from 1,200 to 1,500 m (3,900 to 4,900 ft).
Like all hummingbirds, the coppery-headed emerald feeds on nectar and small invertebrates. Because its bill is short, it forages at small flowers, including those in the genera Besleria, Cavendishia, Clusia, Guarea, Pithecellobium, Quararibea and Satyria. It feeds at all levels in mature wet montane forest and forest edges.
Males form small leks at middle levels of forest edges. source