It was previously considered to be conspecific with the western marsh harrier (Circus aeruginosus) but is now usually classified as a separate species.

It has two subspecies: C. s. spilonotus in eastern Asia and C. s. spilothorax (Papuan harrier, perhaps a separate species) in New Guinea.

The male's plumage is variable; typically the head, breast, back and wing-coverts are blackish with pale streaks.

Large numbers of birds migrate along the Chinese coast with thousands passing through sites like Beidaihe during the autumn.

Its preferred habitat is open country including marshland, paddy fields and grassland.