During my first trip to Costa Rica, the black-bellied hummingbirds did not come to the feeders. However, I was able to track males down in the undergrowth and got a series of shots showing its markings
I researched in my library and did find a picture of a female black-bellied Hummingbird at a feeder.
The Black-bellied Hummingbird (Eupherusa nigriventris) is an endemic Central American found in moist forest and edge at middle elevations on the Caribbean slope from central Costa Rica to western Panama.
The Black-bellied Hummingbird male has a velvet black face mask, throat and belly, and light-colored under tail feathers. The upper plumage is iridescent golden-green. The bend of his wings is rusty-colored. He has a black, long, slightly curved beak.
The female is green above and pale-colored below. She doesn’t have the black markings of the male.
Black-bellied Hummingbird forages for nectar; flowering plants that are visited by this hummingbird include the trees Inga and Pithecellobium, epiphytes (Ericaceae, Columnea, Eleanthus, Norantea), and flowers of Cephaelis, Witheringia, and Besleria. Black-bellied Hummingbird also feeds on small arthropods.