I think it looks very much like Bulwer's too, so I think you were right first time Geoff - it's a common bird in the Taiwan Strait and must occur here.
I agree with all the things Paul says about the shape, esp. re tapered rear end + it also seems to me typical of Bulwer's and very unusual for Wedge-tailed or most other shearwaters that it appears to be flying with its head above - as opposed to out in front of - its shoulders in some of the shots.
I accept, as Geoff clearly does the limitations of these photos, but I think you might find enough experienced observers to say this is Bulwer's from these photos - and there are species on the HK list without photos of any sort having been taken of course.
And finally, concerning size Bulwer's frequently looks bigger and longer-winged than you might expect, especially in shearing flight.
Mike Turnbull
