The natural histories of Volcano (Selasphorus flammula) and Scintillant (S. scintilla) hummingbirds are poorly known. We describe aspects of their breeding behavior with emphasis on courtship displays and sounds that males produced for females. Males of neither species sang undirected song. Males of both species produced a display dive, in which they ascended ∼25 m in the air and then dove, swooping over the female. Both species produced a pulsed sound that was synchronized with abrupt tail spreads during the bottom of the dive. The second rectrix (R2) of both species was capable of generating the same sound in a wind tunnel, suggesting these sounds were made by the tail. The dive sounds of the Volcano Hummingbird were louder than those of the Scintillant Hummingbird. Male Scintillant Hummingbirds produced a wing trill in flight, and performed a shuttle display to females in which the wing-beat frequency reached ∼100 Hz. Males held territories in open areas during the breeding season. Not all territories included abundant floral resources, and abundant resources in closed habitat were not defended. The role of resources is unclear in the breeding system of these two species.