Eastern Marsh Harrier

The eastern marsh harrier is 48–58 centimetres long with a wingspan of 113–137 centimetres, and the female is usually larger than the male. The male's plumage is variable: typically the head, breast, back and wing-coverts are blackish with pale streaks, the rest of the wing is grey with black wingtips and a white front edge, the tail is grey, the rump white and the underparts mostly white. The female is dark brown with buff streaking on the head and underparts, a rump often whitish and a barred tail. (Wikipedia, general species account)

It was previously treated as the same species as the western marsh harrier. Eastern marsh harriers are generally migratory. The breeding range covers northeast China, Mongolia and southeast Siberia as far west as Lake Baikal, with small numbers in northern Japan, and there is some overlap with the western marsh harrier around Baikal, where interbreeding has occurred. The wintering range includes southern China, Taiwan, Korea, southern Japan, northeast India, Bangladesh and Southeast Asia as far south as the Philippines, Borneo and Sumatra. (Wikipedia, general species account)