Arctic Skua
As Mike T has said, there is no doubt that this is an Arctic Skua with its diagnostic pointed central feathers. Also its relatively small-headed appearance with relatively light bill and moderately built body all fit Arctic and rule out Pomarine [heavier all round] or Long-tailed [shorter heavier bill, narrower wings, longer tail and lighter build]. Furthermore, the white flash on the primaries is too wide for Long-tailed and doesn't extend onto the primary coverts like Pomarine.
It appears to be an intermediate type because of its overall darker underparts but not dark enough for dark morph because of its paler streaked neck contrasting with its dark cap, and strongly barred flanks, upper and undertail coverts against a white background [not all dark].
The underwing barring and two-tone bill indicate it is either first summer or second summer. On balance it appears to be second summer because of the adult type head pattern with plain dark cap. Other points in favour of second summer are the grey inner two thirds to upper mandible [with no hint of yellow which can be present in first summer], and the black legs seen as the bird takes flight [they change from light to dark with age]. Would expect the pointed central tail feathers to be longer in second summer, as they get progressively longer with age, but there is considerable overlap between age groups.
Whilst most first summers apparently remain in their winter quarters, a larger proportion of second summers are reported to migrate north, which would explain this June record in Hong Kong waters.
Mike Chalmers
