Green-billed Coucal vs Asian Koel

The bill color is the most reliable field mark: the Green-billed Coucal has a distinctive greenish bill, while the Asian Koel typically has a black bill. Both species can be found in similar habitats, but their vocalizations differ significantly.

Look for the bill color first: greenish in Green-billed Coucal and black in Asian Koel. Listen for vocalizations: deep 'hoop' notes for Green-billed Coucal and 'ko-el' calls for Asian Koel.

The Green-billed Coucal has a more uniform plumage with a greenish bill, while the Asian Koel, especially the male, is glossy black with a black bill. Females and juveniles of the Asian Koel have more varied plumage with spots and streaks.

The vocalizations of these species are distinct: the Green-billed Coucal has a series of deep, resonant 'hoop' notes, whereas the Asian Koel is known for its loud, repetitive 'ko-el' calls.