CASPIAN GULL AT HEATON PARK AND AUDENSHAW RESERVOIRS

A PHOTO ESSAY

by Ian McKerchar

In late 2005 and early 2006, Greater Manchester’s first accepted Caspian Gull rather irregularly and unpredictably graced the nightly gull roosts at either Heaton Park or Audenshaw Reservoirs. As an initially quite controversial bird and given that its 3rd winter plumage is the rarest to observe, this short photo essay is intended to illustrate the main identification features. 

The following images were taken in December 2005 unless otherwise stated (photographer in brackets).

Above: Note the very long neck in this pose, with angled nape and typically small head appearing slightly more rounded here. Compare the colour of the mantle to the argenteus Herring Gull on the left, although the lower scapulars and wing appear slightly darker due to affects of shadow. Very faint remnants of the nape spotting are just visible here as are the brownish feathering in the lesser/median coverts and outer tertials (Ian McKerchar).

Above: Here, taken in dull conditions, the mantle appears unnaturally darker and the base of the bill more distinctly greenish. Note the ‘classic’ pear shaped head, the small ‘beady’ eye, long primary projection beyond the tail and the way the rear end is carried at a very acute angle, high out of the water, which was a consistent feature of this bird (Ian McKerchar).

Above: Again, the head shape is quite distinct and the breast particularly ‘full’ looking while the mantle colouration would be similar to a darker argentatus Herring Gull (Ian McKerchar).

Above: This photo, taken at Audenshaw in poor light, has the Caspian on the far right with a graellsii Lesser Black-backed Gull in the centre and argenteus Herring Gull far left. The dark subterminal bill mark, long wings and darker grey upperparts of the Caspian are obvious (Rob Adderley). 

Above: This the only open winged shot obtained. Any white mirror on P10 would be difficult to make out on this evidence but note the paler, grey inner webs to P7 and P6, quite broad black subterminal band on P5 with prominent white tip and tiny dark subterminal mark on the outer web of P4, just visible (Rob Adderley).

Above:  In brighter light the mantle appears lighter grey and here the bill looks quite long and slim, showing the rather gentle curve to the tip of the upper mandible. Note the protruding breast, long wings and small-headed appearance again, which looks more rounded here (Ian McKerchar).

Above: In this image the bill looks particularly long and parallel sided and the forehead long and sloping but note the upperparts appear paler grey and bill base more yellow due to the strong sunlight (and some image lightning) (Rob Adderley).

Above: Again, the head profile is distinctive in this image and the breast particularly ‘full’ looking although here the bill appears to exhibit a slightly ‘blob-ended’ look, which was a product of this particular photograph and not present in field observations or subsequent images. Note the very conspicuous dark subterminal bill ‘band’ with paler tip (Ian McKerchar).

Above: This image was taken upon the birds reappearance in January 2006, over 6 weeks after the last sighting of the bird in Greater Manchester and again, in strong sunlight (with very slight image lightning) the bill appears more yellowish and the upperparts paler grey. The long sloping forehead, weak goyn angle and parallel-sided bill show well here and the bird still maintains its ‘arse-in-the-air’ posture (Rob Adderley).

Above: Also taken in January 2006 and under the same bright conditions as Fig.9, this image allows a useful comparison of the shade of grey in the upperparts between the Caspian and the graellsii Lesser Black-backed Gull as both birds are under the same lighting conditions and at a similar angle. Importantly, this image clearly shows a small pale mirror on P10, visible on the underside of the far wing (Rob Adderley).

On the whole, once seen the Caspian Gull was very distinctive and easily picked out from the many (often thousands!) of other large gulls at the roosts. Initial doubts over the birds identification arose form afew misleading images (and a small part due to our unfamiliarity with this particular plumage) which portrayed 'illusionary' features or unnatural colouration due to lighting conditions and image quality, highlighting yet again the necessity of obtaining a series of photograph and importantly compiling detailed field notes and not relying solely on our cameras.

Just incase anyone was wondering, the leg colouration was seen, with initial views in dull light showing slightly greyish and views in brighter light distinctly pinkish, so greyish-pink then!

Acknowledgements

I would like to thank Rudy Offereins and Dick Newell for offering their opinions on the identification of this bird, Rob Adderley for his continued discussion, comments and supplying me with his excellent photographs, Pete Berry and Tony Disley for their comments and to all the birders who showed an interest in this highly educational sighting.

Ian McKerchar, March 2006

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