Several populations are given subspecies status. The nominate form with a black bill is found in central and eastern China. The population in Afghanistan, turkestanicus, is often included in the widespread temminckii which has a smaller bill width at the base and is found along the Himalayas east to northern Burma. The population eugenei, which lacks white spots on the median coverts, is found south into Thailand. Cambodia and the Malay peninsula have crassirostris, while dichrorhynchus with smaller spangles occurs further south and in Sumatra. The Javan population, flavirostris, has the thickest bill. The subspecies status of several populations has been questioned.