The term "Green-billed coucal" does not correspond to a recognized or widely documented species within ornithological literature or major taxonomic databases such as the International Union for Conservation of Nature (IUCN) Red List, BirdLife International, or the Handbook of the Birds of the World.
Accurate information is not confirmed regarding the existence of a bird species officially named "Green-billed coucal." The term may represent a misidentification, a local or colloquial name, or a fictional or hypothetical construct.
Coucals, in general, belong to the genus Centropus within the cuckoo family (Cuculidae), and are known for their large size, terrestrial habits, and long tails. Some coucal species exhibit dark or iridescent plumage, but no known species has a characteristically green bill. While certain birds may have bills that appear greenish due to lighting, structural coloration, or individual variation, no taxonomic authority currently lists a species under the name "Green-billed coucal."
Possible confusion may arise from similar-sounding names or misrecorded observations. For example, the Green-billed Malkoha (Phaenicophaeus tristis), found in South Asia, has a pale greenish bill but is a different genus and not a coucal.
In summary, "Green-billed coucal" is not an established or recognized ornithological term, and reliable sources do not confirm its validity as a species.