To me, this bird seems to have black lesser coverts, very extensively white median coverts and broad white fringes to the greater coverts, forming a white wing panel (although curiously this seem more the case on the left side than the right side). I agree that the rump is extensively grey, but to me it seems darker than the mantle. Many of the mantle feathers seem to have very dark centres.
If I had seen it, I would have concluded that this bird was leucopsis (and have done so for similar birds in the past).
