However, clarification is now at hand, because the species has been observed frequently in recent years as more of the island's remote rainforests have been explored. Here, we emphasise and elaborate certain details, and include the first published photographs and sonograms for either species. The genus Neodrepanis is characterised by a tiny body with a short tail, a fine, strongly decurved bill and, during the breeding season, strong sexual dichromatism. Males in breeding plumage are brilliant blue and black above and variably bright yellow below, with extraordinary blue and green facial caruncles. In winter, males are often seen with traces of breeding plumage coloration.
Males are easy to identify in breeding plumage.
Male Common Sunbird Asities are duller than Yellow-bellied in almost all respects. The former have brilliant royal blue-fringed back crown, nape, mantle and scapular feathers, and narrow but fairly conspicuous yellow fringes to the secondaries and greater and median wing coverts. The caruncle is almost square and turquoise-blue, rather greener around the eye. The wing feathers lack the yellow fringes shown by Common Sunbird Asity. The underparts are an intense buttercup yellow.