The Asian Koel is a large, frugivorous cuckoo named for the male’s distinctive loud calls ko-el familiar in urban parks and a variety of open woodlands throughout the Indian Subcontinent, south and east China, the mainland southeast Asia and the Sundaic Islands. Northern mainland populations are migratory. Range expansion has been noted in many areas (1, 2, 3, 4, 5).
It is a brood-parasite, laying eggs in nests of medium to large passerines, particularly crows and magpies (Corvidae), mynas and starlings (Sturnidae), orioles (Oriolidae), drongos (Dicruridae), laughingthrushes (Leiothrichidae), and Long-tailed Shrike (Lanius schach). In contrast to most brood-parasitic cuckoos, nestlings of koels and foster parents usually grow up together.
Male is glossy black, whereas female has predominantly dark brown upperparts with pale streaks and spots varying with populations. It is often treated as conspecific with Black-billed Koel (Eudynamys melanorhynchus) and Pacific Koel (E. orientalis) under the name Common Koel (6, 7). It differs from both congeners in female plumages and having pale bills in all sexes and age-classes. Further taxonomic study is needed to clarify species-limits.