 Seven subspecies have been named but the largely contiguous populations show clinal variation and intergrade with each other. Individuals from northern India (ssp. albirictus) are larger than those from the Sri Lankan population minor while those from the peninsular India (nominate subspecies) are intermediate in size. Race cathoecus is found in Thailand, Hong Kong and China. This race has a much smaller rictal spot and the wings are dark with a greenish gloss. In southern Siam a race thai is resident, but overlaps with wintering cathoecus. Race javanus is found on the islands of Java and Bali. Race harterti found in Formosa has the tail length less than the wing.
