The populations in mainland India, "erythropygia" has the rump patch uniform dark chestnut without any dark shaft-streaks. The tail fork is shallow and the white patch on the inner web of the outer-tail feathers is indistinct. Populations of "japonica" breed in eastern Asia and winter in Thailand, Burma, India and northern Australia. They are heavily streaked on the underside and have faint streaks on the rump. The populations along the Himalayas "nipalensis" migrate to peninsular India in winter and breed from Kulu in the west to Bhutan and Arunachal Pradesh in the east. This population has the rump paler with dark shaft streaks. Subspecies "rufula" of Southern Europe, the Iberian Peninsula east to Baluchistan and Kashmir is resident and winters further south. The chestnut of rump fades to white towards the tail base. The nominate population breeds in Mongolia and Trans-Baikailia wintering in South and Southeast Asia. Subspecies "gephyra" of inner Mongolia is considered indistinguishable from the nominate subspecies. The African populations include "kumboensis" from the highlands of Sierra Leone and Cameroon; "melanocrissus" of the Ethiopian highlands and "emini" of Sudan, Uganda, Kenya and Zambia. Many of the variations are separable only on tail and wing lengths and these vary with overlap across populations.