Article and photos by Brian J Small

In North America, there are a growing number of records of Yellow-legged Gull L michahellis largely of adults, and probably involving the races michahellis and atlantis. This note is designed to give the identification features of juvenile and first-winter michahellis an airing from a North American perspective.

In north-western European countries, the occurrence of michahellis in late summer and autumn has become regular and in increasing numbers. With such a population expansion, there is, with the post-breeding northwards movement, no reason why juvenile and first-winter Yellow-legged Gulls should not occur more commonly in eastern USA in the same seasons. Although written from a European viewpoint, the comments accompanying the images here can also apply to eastern USA when comparing Yellow-legged with American Herring Gulls L (a) smithsonianus.

So how do you go about identifying a juvenile or first-winter (first-basic) Yellow-legged Gull? Basing the discussion on three juvenile Yellow-legged Gulls, but including supporting images of others, I will run through the structural and then the plumage features of Yellow-legged Gull. I will include comparisons with Lesser Black-backed (races graellsii and intermedius) and (British) Herring Gull (argenteus). The discussion about each individual will highlight the crucial features needed for identification, although it will also highlight the variation that exists in the plumage of michahellis. All videograbs are taken using a Sony PC3 through a Leica APO Televid, with a 20X eyepiece.

The structure of Yellow-legged Gull, once learned is a good clue to its identity. When having spent some time looking through a flock of Herring Gulls, you suddenly come across a young gull that looks longer-winged (especially when the wings of Herring are still growing) and longer–legged, slightly more majestic, then is the time to pay close attention. In late July and early August you may also find that the advanced state of moult on the scapulars and inner coverts, plus wear on the tertials, may also help in appearing different.

I will discuss the first Yellow-legged in the most detail, with the following gulls showing the variation. The first, taken on Crosby beach, Merseyside, UK on July 28th 2000 (Figures 1 and 2 below), is the earliest of the images presented here, but it shows all of the features that characterise juvenile michahellis.

It is clearly a large and strong-looking gull with a square head and broad bill, showing a prominent gonydeal point and hooked tip. It is attenuated to the rear, with long wings, probably fully grown, which on graellsii and argentatus is rarely the case so early. It is quite ’chesty’, and shows a good ‘tertial step’. The head and body are much whiter than you would expect for either graellsii or argenteus, although some can seem much whiter and less marked than the literature states. In a North American context, it is much whiter bodied than smithsonianus, and would surely stand out from the crowd.

A detailed examination of the visible plumage shows some interesting features that will help.
The overall tone of the centres to the feathers of the upperparts is much more washed out than you might expect on the other species discussed here – and probably only matched by Caspian Gull L. cachinnans.
The edges to the juvenile scapulars are relatively un-notched and not all that clear cut, with the rearmost scapulars seeming large and dark-centred (a feature I regularly note on juvenile michahellis).
The juvenile tertials are largely blackish with the white marks restricted to the tips, as a white edge at first glance seeming of even width, but faint notches are discernible, but also internal spots either side of the shaft.
There are second-generation scapulars and wing coverts visible, these are distinctly patterned and have been moulted much too early for them to be seen on graellsii or argentatus: the earliest I see this amount of moult on a graellsii would be the last week of August; it is rare to see any new scapulars or wing coverts on argenteus in late August and certainly not to this extent.

Features not visible are the clear-cut black tail band with a totally white base to the tail and virtually un-marked white uppertail coverts, plus the dark under-wing, as in this image (Fig. 3 below) taken of a colour-ringed bird at Blythburgh, Suffolk on 13th August 2000.

The next four video-grabs are of a very different michahellis, one that is about as much like a graellsii as you can get. All are taken at Southwold, Suffolk, UK on 8th August 2000 (Figs. 4, 5,6 & 7)

A close look at this gull is needed to confirm that it is indeed a Yellow-legged. Figures 4 and 6 show the bird largely in profile, and it is apparent how long-winged michahellis is, the tip if the tail is only one-third of the way along the exposed primaries, compare this with a more distant shot of another juvenile at Blythburgh on August 9th (Fig. 8 below). So what are the defining features of this gull, if it is so like a graellsii?

• The head streaking is neat and on a white background, on graellsii and argentatus at such an age it (usually) is on a dingy almost gingery cream background, whilst the body is also well-marked, quite unlike the, expected, clean white belly of the Crosby gull and the majority of typical juvenile Yellow-leggeds. Moult of the scapulars is a little more advanced than on graellsii, and the pattern of the feathers is a little more contrasting.
The wear on the tertials and inner greater coverts shows that this gull is older than the fresh-plumaged graellsii appearing in early August. The pattern of the tertials is unlike argentatus. See Fig. 6.
The pattern of the greater coverts themselves is in fact more like argenteus, with well-notched inner to middle feathers.
The tail band is narrow and, although there is barring on the white tail base, well-defined. Look how on the outer two feathers the tail band narrows and how the base is virtually unmarked white It is rare for graellsii to show such a pattern. In flight the tail pattern was a prominent feature.
The bill is stronger than graellsii and argentatus, and rather skua or jaeger-like. It looks short, but was in fact quite long. A feature I have noted on a number of well-marked juvenile michahellis is the white ‘muzzle’ around the case of the bill.

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