The word “Koel” is derived from the Hindi word which is onomatopoeic in origin.
The Sanskrit root is “Kokila” and the words in various Indian languages are similar.
This bird has a strong association with the Traditional new year celebrations of Sri Lanka. In the literature around the festival, the song of the bird is regarded as heralding the traditional new year. This bird is known as the koha in Sri Lanka by the Sinhala speaking community.
The Asian Koel is a large, long-tailed, cuckoo measuring 39–46 cm (15–18 in) and weighing 190–327 g (6.7–11.5 oz).
The male of the nominate race is glossy bluish-black, with a pale greenish grey bill, the iris is crimson, and it has grey legs and feet. The female of the nominate race is brownish on the crown and has rufous streaks on the head. The back, rump and wing coverts are dark brown with white and buff spots. The underparts are whitish, but is heavily striped. The other subspecies differ in coloration and size. The upper plumage of young birds is more like that of the male and they have a black beak.
They are very vocal during the breeding season (March to August in South Asia), with a range of different calls. The familiar song of the male is a repeated koo-Ooo. The female makes a shrill kik-kik-kik… call. Calls vary across populations.