CLINCHING A CASPIAN

THE OCCURRENCE AND IDENTIFICATION OF A COUNTY CASPIAN GULL

by Ian McKerchar

Caspian Gull (centre) with Herring Gull (right)

On the 1st of January 2008 I found and identified an immature Caspian Gull at Heaton Park Reservoir, the bird was seen on another two occasions in the roost at the site but unfortunately due to restrictions by United Utilities on the release of sightings from the reservoir and it's strictly permit only nature, the bird was not widely observed. This bird became the counties fourth accepted Caspian Gull, after previous records of a 3rd winter and two adult birds.

It's identification was fairly straight forward, although good experience with the species goes a long way to help, but it's ageing is less of a certainty, although I believe the bird to be a 2nd winter. This occasional uncertainty is mainly due to advanced 1st-winters and retarded 2nd-winters appearing quite similar but either way, in this article I hope to explain the features of this bird and extend our understanding of the species and what to look out for if we should come across one in the future. It is very important however to stress that the first starting point should be in gaining a firm and thorough knowledge of other commoner gulls, particularly Herring (argenteus and argentatus), Yellow-legged and Lesser Black-backed Gulls in all age groups. Whilst browsing through gull books may seem like a good starting point, it is perhaps often more likely to just confuse and deter the would be guller, rather, experience of gulls should be obtained by visiting your local roost and searching through the gulls present, not for rarer species (after all how will you know it is one?) but at the aforementioned species, asking yourself the questions, what age is that one, what species is that, why does it look different from the others etc. Take field notes, get used to picking out and naming (correctly!) the feather groups, attempt to age and identify the gulls you see but don't expect to get them all right or to know infact what they are, there are always some that seem to defy any attempts of identification! Once you have looked through the gulls, hopefully noting as much as you can (hence the importance of field notes) compare what you've seen with what lies in the literature but be mindful over oversimplifying the identification of species such as Yellow-legged and especially Caspian Gull, there are many pitfalls and confident identification requires experience and most importantly, a cautious approach. Claiming such rare county species, especially such as Caspian, should only be done with the backing of a full suite of required identification features, getting it wrong is easier than getting it right!

Anyway, the images below were taken on either the 1st or 4th of January and all in rather less than adequate lighting conditions so their quality ranges from not bad to down right awful but they all posses some features we can observe and hopefully learn from. None of the images has been altered in any way other than slight cropping in some cases.

Above: The extension of the primaries beyond the tip of the tail is clearly longer than the distance between the tip of the outermost tertial and the tip of the tail. The typical head shape expected can be clearly seen here, with a rather 'snouty', elongated look to the front of the face and a pear shaped head profile. The head has a strikingly white ground colour although there is some dusky around the eye, note the grey 'shawl' around the nape extending onto the breast here and the small, black, 'beady' eye. The greater coverts, although already exhibiting some barring on the inners, are uniformly muddy brown, especially at the bases more than the tips.

Above: Not a great photo by any means but this demonstrates the typical 'four-toned' appearance of the bird, with white head, grey mantle, brown wing coverts and blackish centred tertials and primaries.

Above: Note the distinctive tertials with very dark, solid blackish centres, only tipped with white which does not extend along the feather edge, giving the typical 'thumbnail' impression and whilst not easy to make out here, the bill is very parallel sided and lacking in any goyndeal angle, overall appearing quite slim. The small 'white' extreme tip, dark subterminally and greenish-grey base of the bill is apparent and the  mantle colour is very similar to argentatus Herring Gull, noticeably darker than argenteus Herring and slightly lighter than Yellow-legged Gull

Above: Yes, yes, I know, what the hell...but this shot of it in flight (infact flying away from the camera) clearly shows the distinctive sharp and well demarcated black terminal tail band clear cut and contrasting against the startlingly white and virtually unmarked rest of the tail and uppertail coverts .

Above: Note the dark secondaries and greater coverts above them looking distinctly and characteristically two-toned with uniform muddy brown bases and paler tips, the unmarked, white tail and clear cut black tail band can still be seen here too

Above: Crap photo, yes, but here in an attempt to show the white, predominately unmarked underwing coverts and unmarked undertail coverts of this bird, plus the solid black tail band of this bird again as it bathes, all indicative of Caspian Gull

Above: Nope, these photos aren't getting any better are they? This photo 'sort-of' (as best as I could obtain that is!) shows the primaries of the upper wing with the very dark, solidly blackish outer primaries and inner primaries with dark outer webs and paler inner webs creating that typical 'Venetian Blind' effect

Above: As a rather small individual, combined with a head shape which could occasionally appear slightly more rounded; it might be fair to say this bird is possibly a female of the species. As for the age of this bird, the mantle showing some 2nd generation (with darker markings) and all grey 3rd generation feathers, the wing coverts and tertials appearing atleast mostly immature, with the clean whiteness of the inner tail and the distinctly paler based bill all seem to point to a 2nd winter, rather than a 1st winter bird.

Ian McKerchar, January 2008

BACK TO THE IDENTIFICATION ARTICLES HOMEPAGE

BACK TO THE MANCHESTER BIRDING HOMEPAGE