Unusual 2nd W Common Gull Larus canus at Helsingborg

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1 Unusual 2nd W Common Gull Larus canus at Helsingborg View PDF at high zoom for optimal picture resolution On 22 nd of March 2015, 3 rd CY Common Gull Larus canus with black markings in tail and to a lesser extent in secondaries was observed at Helsingborg Marina, south Sweden. Additionally, the bird showed many brown lesser upper-wing coverts, while both median and greater coverts were tipped brown and showed an overall brownish cast. Each feature is occasionally observed in this age group of the nominate subspecies, however as here, more seldom in combination. Interestingly, the bird also showed a 1 st W -like under-wing pattern. This set of features is more regularly seen in any of the other recognized subspecies, particularly kamtschatschensis and brachyrhynchus, possibly also eastern heinei. Right. Fig. 1. Common Gull Larus canus, Helsingborg Below. Fig. 2. Common Gull L. canus 2nd W at Helsingborg on From this angle, additional obvious feature is a spotted flank. The white spots (mirrors) in outer primaries are restricted to a small spot on the outermost feather in each wing, in this respect recalling Ring-billed Gull L. delawarensis. Here, the bill can be viewed directly from the side, making accurate assessment of length, depth and overall shape possible.

2 Fig 3. Common Gull L. canus, 2 nd W at Helsingborg on Distinct markings in under-wing, with brown tips to axillaries, as well as under-wing coverts. Additional characters of the Helsingborg Common Gull (hereafter the HCG ) were; Large, all-dark eyes medium to small size, estimated similar to average canus medium to moderately dark grey on mantle, i.e. much as nominate adult canus or slightly darker. Context In a NW Scanian perspective, the HCG stands out among other, daily observed 2 nd W Common Gulls, that comprises the nominate form and probably also a low (but unknown) percentage of ssp heinei. From western Europe eastwards, there is a cline across northern Asia, with Common Gulls becoming larger, larger-billed, darker grey and with increasing tendency to show a pale iris. Interestingly, in the contact area of kamtschatschensis and brachyrhynchus in north eastern Russia and Alaska, the pale eye in some adults continue, while bill size and body size drops radically and colour of mantle becomes paler, indicating a genetic divide. Regarding 2 nd W plumage, this also includes a cline from pale, generally unpatterned nominate canus to well-marked kamtschatschensis (and brachyrhynchus), with heinei intermediate. Heinei, more often than nominate canus, shows black markings in tail and secondaries and while lesser coverts regularly include brown feathers, but like canus, rarely shows more than pale brown tips to lesser and median under-wing coverts (cf. fig. 8). Surely, heinei may well include features of more well-marked kamtschatschensis in overlap area in eastern part of range, regardless of age. In canus, these features are said to be rare, at least in combination, but with up to 5% showing dark markings in tail and/or secondaries in winter in W Europe (Malling-Olsen & Larsson 2004). In Finland, this seems to be more common with up to ¼ in winter with black in tail, thought to indicate heinei (Peltomäki 2000). In NW Scania, a rough estimate is that 5-10% of the 2 nd W Common Gulls show at least traces of

3 black in tail (fig. 7), while obvious black spots are found in less than 2% (pers. obs). Grant (1986) states that canus with prominent traces of secondary bar are rare. Common Gulls of race kamtschatschensis as well as brachyrhynchus regularly show 1 st W characters in 2 nd W plumage (Grant 1986, Malling-Olsen & Larsson 2004). These features include black spots in tail ( ink stains ), ranging from almost complete black band to an all-white tail, a varying amount of black in secondaries, brownish upper wing coverts (especially lesser and median) while under-wing coverts are frequently and obviously tipped brown. Additionally, the tertials often show black spots of variable sizes. For these reasons, in the case of the HCG, it is necessary to consider every option. Identification of the HCG Subspecific identification of Common Gulls is not easy, as measurements and plumage features overlap. In extreme cases however, an out-of-range brachyrhynchus or kamtschatschensis seems possible to clinch in the field with relative certainty, though perhaps only extremes in adult plumage. Regarding the HCG, 2nd W brachyrhynchus, as well as kamtschatschensis and well-marked heinei (or intergrades) can obviously show similar plumage features. Also taking individual moult progression into account, there is little chance in excluding any of the forms from an unusually well-marked nominate canus on plumage alone. To investigate the record further, in addition to the obvious plumage features mentioned above, at least the following characters need to be assessed when dealing with a 2 nd cycle individual: a) Size b) Colour of mantle and upperparts c) Bill size d) Bill shape e) Pattern of neck, breast and flanks f) Head shape g) Eye colour h) Pattern on primaries 9 and 10 i) Black on inner primaries a) Starting with the size of the HCG, when seen in flight, the bird appeared to be within the average dimensions of nominate canus. Without direct comparison to other Common Gulls during the observation, it is probably safe only to exclude kamtschatschensis and, perhaps, also males of heinei. b) The grey shade of the mantle is estimated to number 6 on the Kodak greyscale, putting it in the middle to darker end of nominate canus. This overlaps with (at least western) heinei, brachyrhynchus and some kamtschatschensis. In reality, any serious claim of kamtchatchensis

4 would certainly need for the upperparts to be at least a few shades darker to be taken into consideration at all, preferably grey scale 8 or darker. Breeding individuals of ssp heinei (at least some) in NE Kazakhstan seem to show colour of upperparts close to the HCG. c) From western Europe and eastwards, the bill size increases from canus through heinei to kamtschatschensis and pictures of the latter often show a strikingly long bill, entirely different from the HCG. Some heinei show a bill almost as long as kamtschatschensis, while (not surprising) others are within the normal variation of canus. Many heinei though, show a robust bill, regardless of length. From measurements, brachyrhynchus (aka Short-billed Gull) is the shortest-billed of the four taxa, though even with just a trifle compared to canus. This means a total overlap depending on age and sex. To summarize, the HCG ends up somewhere between a short-billed heinei, a normal canus and normal to long-billed brachyrhynchus. bill length depth at gonys depth at base gonys length brachyrhynchus canus heinei kamtschatschensis (from Malling-Olsen & Larsson, 2004) d) More useful is doubtless the shape and depth of the bill: brachyrhynchus (even with just a few 1/10th of a mm) regularly shows a thinner bill than e.g. canus. Picture studies of brachyrhynchus reveal a spiky bill shape, seldom with a marked gonys angle, with the tip pointing slightly downwards. This recalls Bonaparte s Gull Chroicocephalus philadelphia in shape and Black-headed Gull Ch. ridibundus in size (depth). This combination, rather than length (i.e. shortness), is crucial when identifying an out-of-range brachyrhynchus. The bill shape of the HCG must be characterized as typical of nominate canus, being deep at gonys and with a rather bulbous tip. This implies that brachyrhynchus is unlikely, but perhaps not fully ruled out. Turning to heinei and kamtschatschensis, apart from c), no obvious differences in shape have been found. Some heinei (males only?) show nostrils widening at the distal end, a feature not yet observed in any of the other taxa. This may be caused by a larger bill and needs to be investigated further. The shape of the HCG is well within the variation seen in at least western heinei. e) The neck and breast pattern of the HCG involves brown-grey spotting or flecking, intense in hind neck and forming a thin breast band. In addition, the flecking continues onto flank, reaching as far as ¾ of the wing (fig. 2). This plumage pattern is genuinely rare in canus. In henei, the occurrence

5 of this feature is more unclear. Birds from eastern part of the range, or intergrades with kamtschatschensis regularly show pattern on flanks, but for individuals originating from the western part of the range, evidence for this is lacking. On the contrary, many 2 nd W heinei from the Caspian Sea area in winter and early spring actually show less spotting on breast and neck; pattern consists of small, distinct blackish spots, restricted to crown and hind neck, sometimes forming a thin, poorly defined breast band. No individual with spotting on flanks was detected (albeit derived from a small selection of individuals). The overall pattern on neck and breast shown by these birds is different from the HCG and also many canus observed in winter within NW Scania (but resembles bird in fig. 7 and 11). The studied pictures show this feature to be variable among heinei, but when shown might be indicative of that form (needs further studies). In brachyrhynchus, the 2nd plumage regularly includes obvious pattern on flanks. Additionally and importantly, at least in to February, brachyrhynchus also shows an extensive, smooth velvety greybrown colouration on head, neck and breast, almost as if carelessly spray-painted with a thin, diffuse layer. The diffuse spots regularly continue onto lower breast, belly and vent. This pattern is virtually unknown in 2 nd W canus. By March, body moult in any subspecies reduces the amount of brown and may leave the neck and breast whiter, with scattered, diffuse spots, or in some cases almost all white (fig. 8 and 12), with any streaking or spots restricted to head and neck. In brachyrhynchus, the brown-grey velvety spray paint may still be obvious on head and upper neck well into 3 rd winter (and in adult W). Doubtless, if striving to clinch a 2 nd W Short-billed Gull on the eastern side of the Atlantic, ideally, the velvety spray paint pattern would be a desired plumage feature. The HCG does not show this velvety colouration but photograph studies show that the HCG neck and breast pattern is nevertheless fully matched by some brachyrhynchus. At least, the pattern on the flanks shown by the HCG should be regarded as being outside the normal variation in both canus and (western) heinei, but within the regular traits shown by eastern heinei (and intergrades), kamtschatschensis and brachyrhynchus. f) The head of brachyrhynchus is said be rather small and to show a rounded, high profile. Pictures of individuals of any age regularly show a steep forehead with crown peaking behind the rear of the eye. In combination with a small bill, this gives a neat and diminutive impression. Nevertheless, this not always valid or easy to assess, and of course of limited value in flight. Heinei is said to show a more elongated head and a flatter forehead. While this is true for some and even obvious in flight in some cases, many show at least a canus-like head shape, sometimes also recalling brachyrhynchus, albeit the head in heinei normally appears quite large. The elongated shape in heinei may be more obvious further east, as kamtschatschensis often shows a flatter, longer head which, in combination with a longer, stronger bill, sometimes gives the impression of e.g. a small Herring Gull L. argentatus. This is far from the jizz given by the HCG, leaving kamtschatschensis out of the picture.

6 g) While the eye of the HCG was dark, the rate of heinei or kamtschatschensis showing pale iris in 2 nd W is not known. A pale iris is occasionally recorded in corresponding brachyrhynchus. Still, a dark eye is the rule in any form and does not provide any further clues. h) The HCG shows a small, white spot on outermost primary (number 10) and no white on primary 9. The white mirror is divided in two by the feather shaft and ends c. 20 mm from the tip. Preliminary picture studies indicate that c. 80% of brachyrhynchus show white only on p10, the size of the spot being variable. Malling-Olsen & Larsson (2004) describes white on p9 as 0-30mm, i.e. lacking in some, but does not give a rate for this. For kamtschatschensis, Malling-Olsen & Larsson states that white is often lacking on p9. In canus, the vast majority show white mirrors on both p9 and 10 (pers. obs.) and this concurs with Malling-Olsen & Larsson stating that white on p9 is rarely lacking. No information for heinei is found, but possibly (western) heinei is similar to canus, while eastern birds may approach frequency noted in kamtschatschensis. Never the less, in heinei, the status of this feature is unclear. i) The HCG shows solid black onto p5 while p4 has black on outer web only. In brachyrhynchus, black regularly extends onto p3 (Malling -Olsen & Larsson 2004), while picture studies indicate that up to 50% of 2 nd cycles show black only onto p4. Importantly, black on p4 is as a rule a thick, solid black bar across the whole tip. In canus, black often extends onto p4 but, as in the case for the HCG, mainly only on outer web. More seldom is black also recorded onto p3 (pers. obs.). For kamtschatschensis, Malling-Olsen & Larsson states that dark subterminal marks reach p3, while no information is given for heinei. Brachyrhynchus may show string of pearls (white between black and grey in wingtip) in p4-7 but this seems to be at least uncommon in 2 nd W, while it is regular in adults. This feature is not shown by the HCG. Final approach To summarize the points above, each feature on its own shown by the HCG, is at times seen in any of the four subspecies. Instead, the focus should be on the combination of features. Of these, I consider some to be more important; size, colour of mantle, bill size, bill shape, black in primaries and pattern in underwing. As some of the true clinching features of kamtschatschensis and brachyrhynchus are not shown by the HCG, there is no good case for claiming any of those forms. Instead, while many of the points above are well outside the normal variation for canus, the remaining option is to consider the HCG to be of ssp heinei. Admittedly, there is a gap of knowledge in heinei from the middle or eastern part of the range and appearance of birds and variation in the contact zone with kamtchatchensis. However, some pictures of birds in winter from eastern China show close to identical plumage and upperpart colouration to the HCG. It is yet unclear if these are heinei, kamtschatschensis or intergrades.

7 Variation in NW Scania The variation in 2 nd W Common Gulls in NW Scania during winter/early spring is great and many the above mentioned features are recorded on a gliding scale, from unmarked, typical canus to more marked individuals with the HCG at the extreme end. Below, a selection of pictures, all from NW Scania, illustrates some of the different combinations, also showing the difficulty in drawing a sharp line between e.g. canus and heinei. Fig. 4. Common Gull L. canus, 2 nd W at Borstahusen, October This individual shows a typical set of 2 nd W features, with white tail, no black in secondaries and a limited amount of brownish upper wing coverts, mainly restricted to the lesser coverts. Further traits are mirrors in p9 and 10, black on outer web of p4 only. On the other hand, the bill appears long and the streaking on neck is extensive. Fig. 5. Common Gull L. canus, 2 nd W at Skälderviken on This bird shows all-white tail, but noticeable here is limited black in secondaries. Brownish upper-wing coverts much as in previous individual. Mirrors on both p9 and 10, with black onto p4, restricted to outer web.

8 Fig. 6. Common Gull L. canus, 2 nd W at Råå in March Even less amount of dark in upper-wing coverts, and a minimum of black in secondaries. However, no black in tail, and admittedly, finding 2 nd W birds with even small spots may at times be a challenge in NW Scania. Like previous birds, there are mirrors in two outermost primaries and, more importantly, W -shaped black on p4, while p3 in left wing shows small black spot on outer web (p3 in right wing is possibly missing). Fig. 7. Common Gull L. canus at Borstahusen on This bird shows obvious black in tail, however, not in the form of inky spots, but more like thin streaks. Black in primaries extends only to p5 and there are obvious white mirrors on p9 and 10. No black in secondaries and unusually few dark (lesser) upper-wing coverts. Head actually heinei-looking, being flattish with a long bill and distinct dark spots on hind neck. This is a typical example of mixed characters : some pointing at canus while other are regarded as indicative of heinei.

9 Fig. 8. Common Gull L. canus at Borstahusen on Obvious black in all but innermost secondaries is well beyond the variation normally recorded in NW Scania. Black in tail here is actually in the form of ink spots rather than streaks, but not apparent from this angle. Brownish upper wing coverts are present, but to a lesser extent than the HCG. Primary pattern typical of canus, with spots on p9 and p10, while black on p4 is only obvious on outer web. Slight string of pearls effect in p4-6. Note also the white head and neck, a result of partial moult during spring, compare also with previous individual, photographed on the same date. Fig. 9. Common Gull, at Skälderviken on (same as in fig. 5). From below, this individual shows almost all white under-wing, save for a few weak spots at inner fore-arm.

10 Fig. 10. Common Gull at Borstahusen in October 2013 (same as in fig. 4). Note weak brown tips and edges to lesser and median under-wing coverts and also dark lesser underprimary coverts. There are also weak spots (or barring) onto lower breast. As noted in fig. 4, bill is rather long and neck and breast pattern quite strong. A slight mix of characters that could indicate heinei. Fig. 11. Common Gull at Borstahusen on (same as fig. 7). Also from this angle, this bird looks flat-headed, thus still supporting the heinei. However, under-wing coverts are unmarked and not strengthening the case further.

11 Fig. 12. Common Gull at Borstahusen on (same as in fig. 8). From this angle, the ink stain spots in the tail are obvious, recalling a light version of the HCG. Also the under-wing coverts have distinct dark tips, again approaching, but not fully matching the pattern seen in the HCG. Litterature Grant, PJ Gulls. A guide to identification. T & A D Poyser LTD. Malling-Olsen and Larsson Gulls of Europe, Asia and Northern America. C Helm, London. Peltomäki, J Finland next - Ring-billed Gull. Alula 6, pp Internet The Gull Identification website. Flickr.com, Pbase.com and others Mats Rellmar Tyringegatan 41, Helsingborg mats.rellmar(at)comhem.se Sweden