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Message: <blockquote data-quote="Martin Garner" data-source="post: 1584476" data-attributes="member: 5554">Following a request from Gail Mackiernan last night and subsequent help from Michael Boatwright today in accessing some of the full range of images I think this bird can be identified as a slam-dunk Mongolian Plover. Hopefully these comments are useful and clear enough to follow. From here on I will refer to Greater Sand Plover (generically all forms), Lesser Sand Plover (atrifrons/pamirensis schaeferi) and Mongolian Plover (mongolus/ stegmanni).  My ‘first off’ impressions of this bird are that it does suggest a Mongolian Plover. I know that sounds perhaps a bit over-confident, but that was my gut reaction based on the summer ‘breeding plumage’ still present on head and body (not normally OK for Greater Sand in September) and the bill/ head proportions and the slightly greater ‘rangyness’ compared to Lesser SP; Greater always shows this slightly overlong look to the bill, which seems a product both of the overall bill length and the long nail (though it can be hard to describe) and I just don’t see  a Greater SP bill here. All of the UK records for Lesser/Mongolian Sand Plover have begun as ‘Greater Sand Plover’. I also saw a Greater Sand Plover in Cumbria, England in 1988 which was hotly debated at the time and was thought originally to be a Lesser. All kinds of formula/ photos and measurements were used with this latter bird by proponents of its identification both as Greater and Lesser Sand Plover. The mathematical formulas (bill/ eye, head/ bill, bill/ legs etc) seem to have a tendency to be difficult to apply and a reputation for cancelling one another out as the photographs of birds don’t provide empirical data (like biometrics), so while they can be useful sometimes, so I would prefer to focus to other approaches.To the Virginian bird:1)    Head and Body plumageIt shows clear remnants of worn and moulting summer ‘breeding plumage over the head and especially the underparts. Greater Sand Plover normally undergo at least head and body moult prior to leaving the breeding grounds, so by September should appear to be in ‘winter plumage’ with a few feathers in areas such as wing and tail still to be moulted. Any sand plover still retaining some obvious element of ‘breeding plumage’ to the head and body in August and September will normally prove to be a Lesser or Mongolian Sand Plover. There may be exceptions in regard to moult and vagrants sometimes (though none that I know of), but better to start with the norm.2)    Bill I agree with other commentators that the bill looks fine for Lesser/Mongolian and I don’t see the slightly ‘clownish’ long nail and bill proportions of Greater. Those who also consider the head and bill to be more Lesser -like have already done a thorough job of attempting to explain why, so I don’t need to attempt to repeat that, suffice to say I agree with Killian Mullarney’s assessment on ID Frontiers and (with photos) on Birdforum. 3)    Overall structureIn some shots it looks a long-legged rangy bird. This is subjective but I think Mongolian (versus Lesser) has greater tendency to look rather rangy and sometimes ‘large’, which is maybe why there is a greater tendency for Mongolian to be confused with some Greater S P’s. Mongolian is intermediate in size between Lesser and Greater. In, for example wing length, Mongolian overlaps considerably with Greater, whereas Lesser for the most part does not: Wing length: Greater S.P. = 135 - 155mm, Mongolian S.P. = 128 - 146, Lesser S.P. = 120 - 137.4)    Leg colour and length. Some myths persist over characters related to the legs of sand plovers, which should be laid to rest. The leg colour in all forms of sand plover is variable. Mongolian Sand Plover frequently show long-looking greenish legs. The only useful comment that might be made in regard to leg colour is that very black legs do not normally seem to be found on Greater Sand Plover. Otherwise any combination of grey though greenish can be found on any sand plover. In regard to extension of the toes beyond the tail, Mongolian can show this, no problem.5)    Tail Pattern. There are a several shots showing the tail pattern. The darker central tail feathers are found in Mongolian and Greater Sand Plover but not as far as I know in Lesser Sand Plover (pattern is paler and more uniform).6)    FlanksThis seems to have been barely touched on. While I wish the photos resolved better and were less blurry I can see non-white feathers on the flanks on both sides of the bird. They look pale greyish brown and create a slight ‘grubby’ area here. The feathers are on that area of the flanks that butt up to the normal folded wing position and so can be (partly) obscured by the wings.  In fact photos with raised wings clearly show there is more dark rear flank feathering hiding under the folded wing. Also because the grey-brown colour on such flank feathers is weak and somewhat translucent –looking, it is not very striking and has to be ‘looked’ for. In these photos it is hard because of the distance and quality of the images. Nevertheless, it is clearly visible on this bird in a number of photos, and I hope others can see it too. (Maybe someone with high quality field notes/ drawings has recorded this).  In some shots it just looks like vague browner wash on flanks just below the folded wing but on a few photos (e.g. those by Phil Davis), clear darker-patterned feathers can be seen blowing up against the folded wing (on both flanks of the bird). This is diagnostic for Mongolian being found in 60-70% of birds in winter plumage and so should be expected but not guaranteed. It is not found in Greater or Lesser SP. On Greater and Lesser Sand Plovers the flanks are gleaming white. Occasional ‘fluffed –up’ feathers can look a bit darker as they overlap the brown wing coverts and the colour of the latter ‘shows though’ but that artefact should be discernable as such nonetheless.ConclusionSo I see a combination of state of moult (pro Lesser/ Mongolian); bill proportions (pro Lesser/Mongolian); tail pattern (pro Mongolian/ Greater); and dark mid/rear flank feathering (diagnostic of Mongolian) giving me confidence that, while the features are subtle and have to be carefully read in the various photos, in their combination, the bird can indeed be identified as a Mongolian Plover.</blockquote>

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