Swamp Harrier (Circus approximans) flying rapidly away overhead after snatching a prey bird from Okiwi reserve. I think the prey species in a starling or perhaps a myna, but it is a bit hard to tell as the photograph is not as sharp as I would have liked.

Swamp Harrier (Kahu)
Photo taken by Alexei Drummond on 9 January 2018, Okiwi reserve, Great Barrier island, NZ