Oriental Honey Buzzard (Pernis ptilorhyncus) sub adult male. also known as Oriental Honey-buzzard and Crested Honey Buzzard. Despite its name, this species is not related to Buzzards, and is taxonomically closer to the kites.
The head lacks a strong supraciliary ridge giving it a very un-raptor-like facial appearance. It has a long tail and a short head crest. It is brown above, but not as dark as Honey Buzzard, and paler below. There is a dark throat stripe. Unusually for a large bird of prey, the sexes can be distinguished. The male has a blue-grey head, while the female’s head is brown. She is slightly larger and darker than the male. The male has a black tail with a white band, whilst the female resembles female Honey Buzzard. It breeds in Asia from central Siberia east to Japan. It is a summer migrant to Siberia, wintering in tropical south east Asia. Elsewhere it is more-or-less resident. It is a specialist feeder, living mainly on the larvae and nests of wasps, although it will take other small prey.
The Oriental Honey Buzzard breeds in woodland, and is inconspicuous except in the spring, when the mating display includes wing-clapping. The display of roller-coasting in flight and fluttering wings at the peak of the ascent are characteristic of the genus Pernis.
Thanks to Shiva for helping me to identify.