The Black-bellied Hummingbird inhabits mountain forest on Costa Rica's Caribbean side. Males often forage in the canopy and differ from females in underpart color.
Males have a black face, forecrown, and underparts, with bronzy-green upperparts, rufous secondaries, and white outer tail feathers. Females are pale gray below with bronzy spots on the sides.
It occurs in lower- and middle-montane forest at 900–2,000 m, where males forage mostly in the canopy. Post-breeding downslope movement is described for females.
An extinction-risk assessment has not been added yet.