I got the following mail from Brian...
photo is also uploaded

Dear all,

This weekend, I went to Thika on Saturday afternoon, ducks were on 
every tank, but of the five specialities last week only the Tufted 
Duck and one Spotted Redshank could be found. Forty Pintail have 
moved in. The Thika area has so many ideal swamps and lagoons so 
close at hand to the Settling Ponds, that there is probably a great 
interchange, and probably the two rare ducks will return.

On Sunday I went to the KWS Hippo Camp having never been there 
before, and was well impressed, although try as I did during my six 
hours there, I could not locate the Woodchat, the strong winds could 
well have kept it in cover. 

Before going on to the major observation, there were of interest 20 
Black-tailed Godwit, 6 Spotted Redshank, 2 Temminck's Stints, 
Swamphen, Af Water Rail, 2 drake Common Teal plus all of the usual 
Naivasha waterbirds, including five Ospreys in the air at the same 
time. The most obvious place to bird is the shoreline in front, but 
by heading right along the shore and crossing a few channels, there 
are some wonderfully secluded bays in front of the reeds and 
papyrus, which obviously receive little disturbance. 

Whilst scanning the lake I noticed three large gulls sitting on the 
backs of hippos offshore, possibly nearly a kilometre out. I took 
the accompanying photos, but the gulls kept their frustratingly 
great distance.

My attention was immediately drawn to the largest silvery-backed 
gull, considerably larger than the adult Lesser Black-backed, and 
larger than the immature (presumed) Lesser Black-backed. 

Most features pointed to a Great Black-headed Gull coming into it's 
first summer plumage, but the legs did appear to me to be rather 
pinkish than yellow, although the bird was a long way out.

The bill was pale with a dark tip, but rather longer than heavy, 
unfortunately always kept at an angle away from me, especially when 
I pressed the shutter! This also hid any flat-headed profile in 
comparison with the other two gulls which were far more obliging and 
active. There was a smudge behind the eye as well as a tear-drop 
mark under the eye, which may be a sign of a hood coming through. 
The crown was very white, but a band of grey extended from the eye 
to the nape where it was extensively grey. The underparts were all 
white. The entire upperparts were entirely silvery-grey, apart from 
white tertial tips, the long wings extended well beyond the tail and 
crossed, best seen in the photograph where it casts a shadow on the 
hippos snout. The primaries were all dark lacking any wing mirrors 
of adult gulls. When the bird decided to change to a hippo much 
further out from shore, the broad black tail band was very 
prominent, but the outer-tail feathers (or at least the outer-webs) 
were white, the tips to these darker smudged. The primaries were all 
dark, but the mantle was clear silvery-grey.

All these points match wonderfully with a Great Black-headed Gull 
entering it's first summer plumage, however delve as I might into 
the literature, I can find no reference to the species having 
pinkish tinged legs.

I would like others not only to see this bird, but also to give 
comments on this. My experience with this species was in Delhi over 
twenty years ago, where it was the only large gull present and my 
recollection of the bird is rather dim!

 

Best wishes to all Brian