Dear All,

More on the Naivasha Gull…. 
sorting through Dutch Birding, kindly  lent by Bernd de Bruijn, I 
found the photograph of a first year Great Black-headed (listed as 
Pallas's) Gull, taken in Sicily, (the photo can bee seen in the 
Mystery File at the Photos section of the group).

It does show a remarkable similarity to the Naivasha bird however…..

Whilst the bill appears extensively dark tipped, it does appear to 
have a dark lower mandible.

If the head were turned more to the side, it would doubtfully show 
the same dramatic sloping head.

The head appears small in proportion to the body, whilst the Sicilian 
bird has a proportionately larger head.

The dark nape patch on the Sicilian bird passes much higher, making 
the cap contrastingly white, the Naivasha bird has the nape patch 
much lower, and the result is that the head looks whiter.

The primary tips look much blacker, more extensive and contrasting in 
the Sicilian bird, although the angle makes a difficult comparison 
with the Naivasha bird.

Compare now with a presumed 2nd summer Heuglin's Gull taken in 
Nairobi Park April 2002.

Should the Naivasha bird be of the Herring Gull complex, then it 
would be approaching its' third year. The Nairobi bird is younger, 
but already  shows yellow leg colour coming through, (better seen in 
inset)whereas the older Naivasha bird shows pink legs, feet and 
webbings, fairly uniformly, presumably the final colouration of the 
adult bird.

I have inserted a profile of the Nairobi gull taken at exactly the 
same time, the main picture shows the birds head slightly tilted and 
looking back. Note how this completely changes the apparent bill/head 
ratio, and depth of culmen, making comparisons with anything other 
than perfect side profiles misleading.

The Nairobi bird has a pale lower mandible base, but dark upper 
mandible, the Naivasha bird is the reverse of this, although there is 
always a possibility that the apparent dark base to lower mandible of 
the Naivasha bird is caused by shadow. As can be seen the sun was 
high demonstrated by the shadow on the hippos head.

This is just more food for thought, hopefully to eventuate in a 
conclusive identification.

all the best,
Brian