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Adult winter Caspian Gull Larus cachinnans

Summary of Important Features

(Click on any of the thumbnails on the left for a larger image and more text).
In late winter this age becomes perhaps the most difficult to identify, up until this time the majority of Herring Gulls have streaking on the head (usually quite heavy), whilst Caspian and Yellow-legged are unmarked (or virtually so). Key features are structure and plumage details, in particular head and bill shape, tone of mantle and a detailed note of P10 pattern.

Usually a very large gull, with a long primary projection. The head is small with the crown typically rounded, a slight crest noted on some occasions when at rest - when the head is lifted up it is very like a Common Gull. The bill and legs are long, the bill being particularly noteworthy.

Plumage

Head

• Virtually unmarked white at all ages, by early September a few brownish streaks may be just just visible on the hind neck and above the eye. The remainder of the underparts are white.

Mantle

• The mantle tone is frequently very close to that of Common Gull; in direct comparison with argenteus Herring it is darker and alongside michahellis it is paler or equal in tone.

Tertials

• These have narrow white tips and are held flat against the body giving a flat-backed appearance.

Primary moult

A little later than michahellis in my experience, matching that of Herring. In early August an adult had the outer two primaries faded black with P10 having a whitish inner tongue, a white mirror and narrow sub-terminal band. By September, P10 was still retained, P9 was just beginning to grow; P8 was virtually fully grown. The typical pattern of P10 for Caspian is described previously.

Bare parts

Bill colouration changes from a green-yellow in July to a more grey-green colour by September and pale or even richer yellow by mid winter. The eye often appears dark in comparison with argentatus, but may in close views appear pale. The legs are long, thin and coloured flesh, very rarely are they yellow.
Adult Caspian Gull (standing)
Adult Caspian Gull (centre)
Adult Yellow-legged Gull michahellis

Brian Small 1999

e-mail Brian Small

References

Jonsson, L, 1998. Yellow-legged Gulls and yellow-legged Herring Gulls in the Baltic, Alula 3/1998: 74-100

Garner, M and Quin, D, 1997. Identification of Yellow-legged Gulls in Britain, British Birds 90: 25-62

Garner, M, Quin, D, and Glover, B, 1997. Identification of Yellow-legged Gulls in Britain 90:369-383

Harris, A, Shirihai, H, and Christie, D, 1996. Macmillan Birders Guide to European and Middle Eastern Birds

Shirihai, H, 1996. The Birds of Israel, Academic Press, London

Bakker, T, 2000. Birding World

Web sites

Martin Reid www.martinreid.com - armenicus, michahellis, cachinnans

Bob Lewis www.bway.net/~lewis/birds/gulls.html - argentatus, michahellis

Steve Hampton www.west.net/~dj/gulls.htm - michahellis, cachinnans, barabensis, armenicus

Rudy Offereins www.geocities.com/RainForest/Jungle/7550
4th-winter Yellow-legged Gull michahellis
Adult Yellow-legged Gull michahellis (flight)