Male Black-bellied Hummingbirds give the species its name, with their black underparts that extend up through the face to the forecrown. Females, on the other hand, are light gray below. Both males and females are mostly bronzy green above. Black-bellied Hummingbirds live in cool, wet forests and bordering shaded pastures or coffee plantations in the highlands of Costa Rica and western Panama. Males usually spend most of their time in the canopy visiting epiphytes on trees and guarding flowers that are not already claimed by dominant hummingbirds. Females, on the other hand, are more likely found in the understory along edges or forest gaps.