The black sicklebill (Epimachus fastosus) is a large member of the birds of paradise family, Paradisaeidae. This species is found throughout most of central New Guinea and the Vogelkop region to the northwest in montane forests at altitudes from 1800 to 2150 m.
As being the second longest bird of paradise species (behind the Ribbon-tailed astrapia), the black sicklebill measures about 110 cm in length if the tail is included, and around 63 cm without the tail. The female is around 55 cm in length. The black sicklebill is a very bizarre species of bird of paradise. The male has a black head with a long, silver, slightly downcurved bill (not as downcurved as Drepanornis sicklebills), a bright yellow mouth, scarlet-red eyes which are surrounded by iridescent scaly feathers of typically blue-greenish color that cover most of the front of the face. The rest of the head, including the neck, is jet black. The back is jet black, but is mostly covered with iridescent scale-like feathers with metallic blue color, but can be concluded as greenish-blue in some lights. His wings are black with a less conspicuous bluish iridescence. The greatly exaggerated tail is jet black with a more visible blue iridescence, more notable at the center. On its underside, he has very soft, almost silky brownish-black plumage that ends in relatively elongated flank plumes that extend slightly past the tail, but these plumes are more pronounced in the Brown sicklebill. Typically hidden when perched, the males' most splendid ornaments are two glorious pectoral fans on each side of the breast. These large feathers are almost entirely black, but an outstanding feature is that each feather is intricately tipped iridescent blue-greenish. These fans are used in their courtship displays when they bring them up over their head to form an overall comet shape edged with a stroking narrow, blue line. The female, however, is generically unimpressive. She is an olive-light brown above with more of an orange-brown crown. She is creamy on the belly, which is covered with black barring. She still has a long tail, but not nearly as long as her male counterpart. She differs from the female brown sicklebill by her brown eyes vs. the white eyes of the latter species. The tail is a dull olive. Both sexes have grey-blackish legs and feet.