For birders all over the world
The probable identity of the gull Larus sp. at Kings Lynn, UK
Images taken on 30th July 2000 by Brian J. Small. Surfbirds.com or Brian Small would be grateful for any feedback offered, or opinions about the identity of this gull. At the moment we have an open mind about its identity.
Discussion below by Brian J. Small
All images taken using a Sony PC-3 through a Leica APO Televid 20X or 30X eyepiece.
|Just when you begin to think that you have got large white-headed gulls sorted, along comes one that totally confuses. The gull at Kings Lynn (hereafter KL gull) is one of these. In my opinion it is a Caspian Gull, but one that is, for most birders, outside the current accepted norm for this species, and I intend here to put my reasons for this.
The confusion surrounding or, rather, questioning of the gulls identity, is largely a result of a lack of information on the plumage of this, and other, species in late summer. Most images present in the birding press are taken in the winter or spring, and many birders have an impression of Caspian in autumn based upon Lars Jonssons photo in Alula, taken in September. We are still pushing the envelope in gull identification; the KL gull has certainly stretched it a bit.
I feel that I am lucky, and have had a bit more insight, as a result of finding a typical first-summer Caspian Gull at the Blyth estuary, Suffolk, UK, only two days after seeing the KL bird. Also, I have had much correspondence from people and I am grateful to Richard Millington, Rik Winters, Peter Adriaens, Visa Rauste and Dick Newell for their informative and knowledgeable comments. The general consensus is that it is certainly not a Heuglins, most likely a Caspian, but (a remote possibility in my opinion) possibly a hybrid cachinnansxmichahellis or xargentatus.
A detailed study of the plumage of both gulls showed so many similarities that I feel that they have to be the same. In fact the only odd or different thing about the KL gull is its structure (in particular head and bill structure) - Rik Winters who has had more experience than I in Holland, says that it matches the largest Caspian Gulls seen there.
Lets look at the plumage of the Kings Lynn gull closely (what follows is out of necessity very detailed)-:
Now we are getting to the confusing features. The mantle and scapulars were an admixture of dark spots or diamonds (forming rows), greyish or brown-grey feathers, with, or without, a slightly darker sub-terminal line, and (particularly towards the rear scapulars) those that had a darker brown-grey base, and two bars across white or grey. Most of these tended to look quite worn these were similar in pattern to that shown by the Greater coverts. Compare this with the Blyth Caspian and we can see the similarities: the rows of dark diamonds on basically grey or (along the lowest scapulars) brown-grey with thin darker sub-terminal lines; the rearmost scapulars had dark bases with two darker bars across white. The only thing which we expected the KL gull to have were the rather contrasting white scapulars, with large black diamonds at the base and thin black lines extending to the tip. These feathers are those which have been used to support the hybrid theory, but my observation would show that they in fact normal for Caspian in late July or early August. Why seek a confusing answer when a more obvious one is already there?
The new inner eight primaries on each wing showed from above a Venetian blind effect, with darker grey outer edges contrasting with silvery white inners, darkening towards the outer edge where the dark outer edge hooked back to form darker tips. From below the effect was to produce a virtually white hand with a dark or blackish trailing edge. Compare this with the (admittedly poor) images of the Blyth bird and the same pattern is visible.
|Please send us your comments and opinions .|
|This flight shot was taken on August 3rd. All other Caspian shots taken on August 1st|