Long-tailed male is dark above with a paler belly; in good lighting, note his wine-red back and breast and a purplish-blue crown. Midnight-black throat distinguishes him from otherwise similarly-colored sunbird males. Female is much duller, being predominantly greenish-brown with paler underparts, a gray wash over the head, and a pale rump patch; this last feature distinguishes her from most other sunbirds in range, except Fork-tailed and Gould’s Sunbirds, both of which have yellower underparts. Black-throated’s song is composed of shrill phrases of very high twittering trills, often slurred. Calls include high-pitched buzzy squeaks and chip notes.