Great set of gull pics. Eight species on one tide [if you count Vega]! Just goes to show how good HK is for gulls in late winter.
Interesting to see the albino/leucistic Black-headed Gull in pic 1. I saw a previous one in Castle Peak Bay in March 1975 [see note in the 1977 Bird Report]. Olsen & Larrson note aberrant birds are not infrequent in this species.
As for your Vega gulls, see seperate discussion by Geoff of Owen's pics of same birds.
Mike Chalmers