A little-known cuckoo from lowland rainforest. Slender with long, thin bill that droops at tip. Males have dark cap, and red eye and eye-ring. Females have grey head and dark bill. Perches upright and motionless in sub-canopy. Voice a whistled, 2-note call with short first note, followed by loud descending note, “pu piiuuu!”. Similar to Tawny-breasted Honeyeater, but Long-billed Cuckoo is much less active with barring on the undertail. From Dwarf Koel by lack of white face mark and longer, thinner bill