Candidate 3cy American Herring Gull, Seton

This strikingly marked imm “Herring Gull” leapt out at me on the Seton Burn, 15:28hrs on 3/12/22. Mantle a shade lighter than neighbours, with a hint of pastel blue, but massively contrasting heavy nape and flank streaking extending to the belly. These are all good initial clues to identification of an American Herring Gull, but given the variability in so many aspects of immature gull plumages a careful analysis is needed to establish the required suite of features to confirm ID. Fortunately with 90s of video recorded, as well as 40+ photos, many features could be checked, though views of the inner wing were limited to when it was partially open for preening (viewing from side and rear), while the tail was seen well but not fully spread.

The first essential step is to establish the age. Though nearly all plumage features, and bare parts, might give clues to age, the critical ones are the primary pattern, in particular whether the feathers have been replaced with third cycle feathers which are pale grey (not mixed with brownish) in the inner primaries and, critically, showing proper white “tips” to the feathers (big in inner wing and progressively smaller to outermost). While the image quality is not great, there is no doubt that these features can be seen – careful scrolling through the video enabled to establish that the feather with the dark subterminal mark is P4, thus P5 has a big white tip (also just visible in closed wing), P6 a quite small one and then tiny tips out to both P9 and P10. This is a typical pattern for 3cy American (European Herrings are essentially the same but tend to have more extensive white tips in outer primaries, especially in argentatus). Further support for the age is seen in terms of the moult step and greyer replaced primary (3) and secondary (1) greater coverts, as well the mainly white under/upper tail coverts, rump and vent, the white underwing and the good overall progression of moult with the scapulars completely replaced in pale grey, along with the upper tertials, though apart from coverts moult none of the latter on their own are definitive (but also American Herrings, especially from the East coast, tend to be more retarded in appearance compared to European, i.e. having on average more brown feathers in the scapulars).

Now coming to the identification, the critical features are the black or very dark brown colours in the tail, the secondary bar and the bases of the tertials. The tail is certainly quite striking, appearing entirely a solid black colour, save for a faint white subterminal band (which is expected, even in birds with otherwise solidly black tails). Careful analysis of all the footage, including the video, shows that it is otherwise certainly entirely black, even in T6 up to the position where the retrices disappear into the tail coverts, with no sign of the white in the base of the tail edge (which would be expected even in a 2cy Herring Gull). In addition the secondary bar also is consistently blackish (visible in rear views below the coverts when wing drops while preening, and even in the underwing when wing raised while preening), and the bases of the unmoulted tertials also appear as either blackish or very dark brown, depending on the angle. A good supporting feature is the contrasting dark brown greater coverts bar (with one replaced greyer feather as noted) which is also typical for 3cy American.

Further reflecting on this proposed identification and information in the literature, it is known that an all dark tail is characteristic of American and these critical features of dark blackish markings in tail, secondaries and tertials, when viewed in conjunction with the heavy nape and flank marking and strong contrast in the mantle, therefore all point towards identification as American. In their seminal identification paper, Lonergan & Mullarney (2004) highlight the significance of tail pattern in particular:
"While there is extensive overlap in the tail patterns of second-winter smithsonianus and European Herring Gulls, it seems that even the most extreme examples of the latter usually show a narrow wedge (widest at the base) or ‘sliver’ of white along the outer edge to the tail (shown by some smithsonianus too but a definite lack of white edges may be significant).

This example of a 2cy European Herring with an unusually black tail still shows obvious white in the edge of closed tail: https://chrisgibbins-gullsbirds.blogspot.com/2011/03/herring-gulls-variability-in-first-and.html. The same is true for this example for a 3cy with an unusually dark tail: https://www.flickr.com/photos/johnswildlifephotos/24854194186

In fact by 3cy most European birds have much less black, quite often just faint residual marks (e.g. http://www.gull-research.org/hg/hg3cy/3cynov06.html), while American can retain a nearly entirely black tail (e.g. http://gull-research.org/smithsonianus/smith3cy/3cydec002.html, http://gull-research.org/smithsonianus/smith3cy/3cynov02.html). Immature gulls are of course hugely variable in appearance, but while it is very true that some immature American Herring Gulls can therefore not be definitively identified, extensive dark in the tail at 3cy age should be diagnostic.

Next, on tertials, Lonergan & Mullarney (2004) state:
"Many show extensive, sharply defined, solid-black/blackish-brown markings towards the bases of some tertials, usually, the middle and/or outer feathers. Such definite, blackish markings as in the best-marked smithsonianus are seldom, if ever matched by European Herring Gulls.

Finally, for the body, Lonergan & Mullarney (2004) state:
"The dark head, neck and breast-markings of third-winter types average heavier and more blotchy than in European Herring Gulls, especially argentatus, on which these markings tend to be paler and less extensive. On the most heavily marked birds, the density of dark spotting, especially on the hindneck and breast, is strikingly different from anything usually seen in Europe but a few ‘dark’ sub-adult argenteus can be similar".

To conclude, while the resolution in the images obtained falls a way short of what would be ideal, I believe it is sufficient to see key features on this individual which should permit an indicative identification. Indeed had it been lacking in some of those features, in particular the very heavily marked nape and flanks, there is a good chance I would never have noticed it in the first place. Looking ahead, such an individual should remain pretty distinctive in appearence at least while aged 4cy, and probably beyond, so the hope now is that it can be seen again – a main purpose of this short account is to alert people to be on the lookout for further sightings, whether here or further afield…

References

• Adriaens, P. & Mactavish, B. (2004) “Identification of adult American Herring Gull”, Dutch Birding 26: 151-179
• Dubois, P.J. (1997) “Identification of North American Herring Gull”, Brit. Birds 90:314-324
• Howell, S.N.G. & Dunn, J. (2007) “Gulls of the Americas”, ch. 25, Peterson Reference Guides, Houghton Mifflin Harcourt
• Lonergan, P. & Mullarney, K. (2004) “Identification of American Herring Gull in a western European context”, Dutch Birding 26: 1-35 [Presented and illustrated on the Gull Research Organisation website: http://gull-research.org/smithsonianus/1cyoct.html]
• Mullarney, K. (1990) “American Herring Gulls in Ireland”, Birding World 3:96-100
• Olsen, K.M. & Larsson, H. (2004) “Gulls of Europe, Asia and North America”, Helm
• Van Duivendijk, N. (2010) “Advanced Bird ID guide, The Western Palearctic”, New Holland