Taxonomy
The Asian Koel was originally described by Linnaeus as Cuculus scolopaceus based on a specimen he received from the Malabar region. The species has variations within its wide range with several island populations and a number of taxonomic variations have been suggested. The Black-billed Koel (E. melanorhynchus) of the Sulawesi region and the Pacific Koel (E. orientalis) of Australasia are sometimes considered conspecific with the Asian Koel in which case the "combined" species is known as the Common Koel (E. scolopaceus). Due to differences in plumage, colour of bill and voice, the three are increasingly treated as separate species. Alternatively, only the Black-billed Koel has been considered as a separate species, or the Asian Koel has included all subspecies otherwise included in the Pacific Koel, except for the subspecies breeding in Australia, which then has the name Australian Koel (E. cyanocephalus).
The Asian Koel has several geographic forms that have well marked plumage differences or have been geographically isolated with little gene flow. The following is a list of named subspecies with their distributions and synonyms as given by Payne:
- Eudynamys scolopaceus scolopaceus (Linnaeus, 1758). Pakistan, India, Nepal, Bangladesh, Sri Lanka, Laccadives and Maldives.
- Eudynamys scolopaceus chinensis (Cabanis and Heine, 1863). Southern China and Indochina, except the Thai-Malay Peninsula.
- Eudynamys scolopaceus harterti (Ingram, 1912). Hainan.
- Eudynamys scolopaceus malayana (Cabanis and Heine, 1863). Thai-Malay Peninsula, Lesser Sundas and Greater Sundas, except Sulawesi. This may include the race dolosa described from the Andaman and Nicobar Islands.
- Eudynamys scolopaceus mindanensis (Linnaeus,1766) (includes E. s. paraguena from Palawan, and E. s. corvina from Halmahera, the Philippines (including Palawan and the Babuyan Islands), islands between Mindanao and Sulawesi, and North Maluku, except the Sula Islands.
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