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IDENTIFICATION

Above: A typically immaculate and elegant adult Yellow-legged Gull at Audenshaw Reservoirs, late December 2006 (Rob Adderley)

Whilst the identification of adult Yellow-legged Gulls may seem straightforward enough there are in fact many variables and pitfalls for the inexperienced, let alone the experienced! Very few birders take the time to familiarise themselves with the huge variation in Herring Gulls, ask yourself these questions: exactly what is the distribution of black on the primaries on an adult Yellow-legged Gull and how does this compare to the argentatus Scandinavian race of Herring Gull, how variable is their head shape and what is the moult timing of primaries in adults? If you've answered these questions confidently then your likely one of those strange birders who is often termed a 'guller', 'larid lover' or simply 'gull bore/nerd'!

It is can be a rather long winded subject, complicated by the changing appearance of various similar species through the year but close, careful study and a full suite of characters from any suspected Yellow-legged Gull should facilitate a correct identification. This article is not intended to cover everything involved in the identification or pitfalls of Yellow-legged Gull (afterall will the fact that they have triangular shaped nostrils really assist you in the field?), it is intended to be a first step, an introduction, those wanting more should consult the excellent literature mentioned on the previous page.

In a nut-shell...

In comparison with Herring Gull, Yellow-legged Gull is on average an altogether more elegant bird, the head is fuller (especially on the forehead), rather more flat-topped and squared in profile, Their bill is often rather thick and particularly blunt tipped with a steeply curving culmen and they have longer wings with the distance from the tip of the tail to the tip of the longest primary clearly equal to or longer than the distance from the longest tertial to the tip of the tail (see the image above again to re-iterate these features).

Above: Although this individual is in fact a 3rd winter bird (4th calendar year), it demonstrates the head shape and thick, blunt bill to very good effect, Heaton Park Reservoir, March 2008 (Ian McKerchar)

Above: This bird too shows the same characteristics of head and bill shape as well as the long looking wings and is also a 3rd winter bird (4th calendar year). Heaton Park Reservoir, March 2008 (Ian McKerchar)

Above: Even here in this somewhat 'record shot', this adult exhibits typical characteristics for the species, especially considering it is taken in September. It's combination of such a dark shade of grey on the mantle and wings combined with a generally whitish head with only neat, fine streaking and that fuller (especially on the forehead), squarer head shape is conclusive, the wings however appear short due to moult, itself often a distinguishing characteristic. Heaton Park Reservoir, September 2007 (Ian McKerchar)

The upperparts of Yellow-legged Gull are a shade darker grey than our own British argenteus Herring Gull and are similar if often even a shade darker than those of Common Gull though the nominate Scandinavian argentatus race quite often approach or equal the mantle colouration of Yellow-legged Gull and pose problems for the unwary. The wingtip pattern is of more black and less white than Herring Gull, displaying black on 6 and sometimes 7 of the outermost primaries, a feature not dissimilar from our own argenteus Herring Gull (but which has of course a significantly paler grey mantle) but visibly different from that of the darker mantled argentatus which has a pattern of more white and less black. The fifth primary (counting from the outermost) is p5, and should have a broad and unbroken black band across the tip, something argentatus again lack.

Above: This individual is in primary moult and is missing the outer 3 primaries but the broad black tip to p5 is still evident as are the yellow legs and the darkness of the grey mantle and wings. On average Yellow-legged Gulls moult their primaries earlier than Herring Gulls and the primary moult (if present) of any potential Yellow-legged Gull should be noted. Pennington Flash, September 2008 (Ian McKerchar)

Above: The same bird as in the above image: concentrating on the far (right) wing, we can clearly see the outer 3 primaries (p8-p10) still very short and growing. Pennington Flash, September 2008 (Ian McKerchar)

Above: Note the amount of black in the primaries, appearing as a broad 'wedge' and the thick black band on p5, note also the small 'lozenge' shaped white mirror on p10 and the tiny mirror on p9. Pennington Flash, January 2009 (David Winnard)

Above: This terrific shot again demonstrates the amount of black in the wing tips of this near adult bird (in fact a 4th winter), any Yellow-legged Gull should display black on atleast 6 outer primaries (p10 down to p5 atleast) and occasionally even more. The thickness of the bill is evident even in this flight image and the bird's wings are rather broad although difficult to judge without comparison. Pennington Flash, January 2009 (David Winnard)

Above: Again the black in the wingtips is palpable here as is the bulk of the bird's bill. In the field this individual's size and overall bulk was such as to suggest it was a male but the slight black subterminal marks on the bill and black in the primary coverts of the wings suggest the bird was in fact a 4th winter. Pennington Flash, January 2009 (David Winnard)

Above: Extensive black is again visible in the primaries here although in this instance the white tip to p10 is virtually complete with the mirror and the black band on p5 is perhaps at the extreme end of what is acceptable for the species. Audenshaw Reservoirs, December 2006 (Rob Adderley)

Above: Highlighting it's not all plain sailing however, this adult's head shape appears altogether less 'normal' and in fact slightly more Caspian Gull like in this particular image and the un-cautious observer could well jump to the wrong conclusion, once again proving the need for a full suite of characteristics to be obtained. Audenshaw Reservoirs, October 2006 (Rob Adderley)

Yellow-legged Gulls tend to be very white-headed, lacking in extensive, strong streaking during the winter months although they can display some neat, fine streaking around the eye and over the crown early in the autumn (often referred to as appearing like earphones). Herring Gulls on the other hand, especially those darker mantled birds of the argentatus race show coarse streaking creating a messy head pattern but it should be borne in mind that from as early as the beginning of December many British argenteus Herring Gulls can be very white headed and form a trap for the unwitting but their paler grey mantles atleast, should facilitate in excluding any confusion. The Scandinavian argentatus race of Herring Gull form an even higher potential for confusion and are dealt with on the next page under 'pitfalls'.

Above: This adult Yellow-legged Gull exhibits the characteristic head streaking present during the autumn, it is fine and neat, confined around the eye and over the crown. Once again note this bird's very short primaries due to moult. Pennington Flash, September 2008 (Ian McKerchar)

Above: Again this bird shows neat, fine streaking around the eye and across the forehead and also encapsulates the jizz of the head and bill to good effect, It's short primaries are once again due to moult. Pennington Flash, September 2008 (Ian McKerchar)

Above: A handsome, elegant bird displaying a full suite of characteristics, including long primaries with small white tips. Pennington Flash, January 2009 (David Winnard)

The orbital ring of adult Yellow-legged Gull is blood red, creating a darker-eyed appearance when compared to Herring Gull (which can look obviously 'white-eyed') and if one is lucky enough to see one not sat in the middle of a reservoir (not too common in our county!) their yellow legs are usually obvious and particularly long looking, although they vary from a rich yellow to a more subdued yellow for adults (most often in the winter months). Of course judging the actual colour of legs is often precarious as surprisingly, differentiating yellows from fleshy tones can be subjective so caution is advised, when they're yellow, they're usually obviously so! Yellow legs are not however, confined to just Yellow-legged Gulls and Herring Gulls, particularly individuals from certain areas of Scandinavia and the eastern Baltic regions (occasionally but perhaps inaccurately referred to as the omissus race) can show clear yellow legs and such birds have been identified in the county before. Such birds can present the observer with a serious headache and call for a careful assessment of jizz and primary pattern in order to eliminate Yellow-legged Gull.

Above: This individual's long legs are plain to see as is their vibrant yellow colour but it's head shape is slightly less than characteristic in this instance. Audenshaw Reservoirs, October 2006 (Rob Adderley)

Above: Long legs yet again although their colouration looks less vibrant here. The head shape shows well and the head streaking is typical of the time of year. Pennington Flash, September 2008 (Ian McKerchar)

PAGE 3: MORE THAN JUST A MANTLE- SHADES OF GREY AND PITFALLS

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