A small, sunbirdlike bird of lowland and foothill forest. Long, thin, curved bill with olive upperparts and head. Southern birds have a brighter yellow belly and northern birds are more olive below. Similar to several other species, but Yellow-bellied Longbill lacks the gray chest of Spectacled Longbill and female Black Sunbird, lacks the yellow eye-brow of female Olive-backed Sunbird and lacks the contrasting yellow-throat of the higher elevation Slaty-chinned Longbill. Song, an often descending series of downslurred whistles.