Eastern Marsh Harriers breed at Yeyahu Nature Reserve in Beijing. They are one of the star birds of any visit from late March through to October. The spring males are simply stunning and quite different from the closely-related Western Marsh Harrier, some almost resembling one of the other regional specialities, Pied Harrier. Adult females also look very different from Western Marsh and, in my experience, it is only really juveniles/first winters/probable 2 cy birds that could be mistaken for Western Marsh.
I couldn’t find any literature on aging or sexing Eastern Marsh Harriers (is there any out there?). So here are some images of adult males, females, a probable first summer and juvenile birds with some personal comments. Comments from others are very welcome. Having had a bit of difficulty separating a dark juvenile Pied recently, I have much to learn about these wonderful raptors.