Putative Azorean Gull at Stanwick

There are two accepted British records of Azorean Gull, the atlantis race of Yellow-legged Gull, based upon two individuals, one of which was a well-travelled bird that visited Northamptonshire in 2013, 2014 and 2015. Is this another, or the same returning individual in a different guise?

On Wednesday, 4th October, Steve Fisher found and photographed a good candidate for an Azorean Gull at Stanwick Gravel Pits. It appears to be the same bird which he also saw there briefly on both 8th and 15th September. Steve’s images, below, pretty much capture all the visible features, so, is it one?

Head and mantle
This bird does not have a full winter hood and so doesn’t immediately resemble the returning adult from 2013, 2014 and 2015, accepted as the second British record by BBRC. It has been said that the extent of the winter head streaking can vary from year to year in the same individual but this remains to be proven – unless anyone knows otherwise. In any case, the returning individual over those three years appears to have exhibited consistency in the extent of its head streaking, always giving the bird a strikingly hooded appearance. Additionally, the mantle of that bird appeared darker than that of this autumn’s individual, although light conditions, camera settings and processing can, of course, serve to distort the true colour. Having said that, in comparison with the Yellow-legged Gull in the image below, there appears to be little difference in mantle colour. Extent of winter hood varies considerably in Azorean Gull – see here, for example and the bird is not too dissimilar to one, also thought possibly to be Azorean Gull, which visited Shawell in Leicestershire in September 2012.

Wing pattern
The upper and lower wing patterns are interesting and look like they could fall within range of variation for Azorean Gull. There is a single mirror on P10, separated from the small white tip by a narrow black band and no mirror on P9, where Yellow-legged Gull usually has a small mirror. P5 shows a black subterminal band. The underwing shows darkish grey secondaries and primary bases contrasting with white coverts – perhaps not as dark as may be expected for Azorean Gull. Questions: is the mirror on the upper side of P10 too extensive for Azorean Gull? It looks OK on the underside. Is the subterminal black band on P5 too broad for Azorean Gull?

Moult
According to literature (specifically Olsen & Larsson – Gulls of Europe, Asia and North America), Azorean Gull moults earlier than Yellow-legged, which fits with the Stanwick bird which is still growing P10 but everything else, including secondaries and tail, appears to have been completed. Yellow-legged might be expected to still show more signs of moult at this time of the year (but not always).

For reasons stated above, it is clear this is not the same individual as has already occurred here in previous years. So, a very interesting bird, then. Comments welcomed.