One of the numerous disadvantages to birding in the Midlands is that you do not see large numbers of many species which are plentiful at the coast. As a result you may not be familiar with the full range of variation which can occur within the limits of a given species range. Having said that, the comparative rarity of many birds can result in your spending large amounts of time looking at them, perhaps increasing the likelihood that odd individuals will be detected.
The fields around Woolscott recently played host to a flock of eight Whimbrel and I spent a large amount of time watching them principally because I really like Curlews, Whimbrels and their allies and partly because they were so close to my home. After a couple of days I noticed that one of the birds appeared to be showing an increased amount of barring on the rump in comparison to the rest. This reminded me of birds I had seen in Australia where the ‘eastern’ race variegatus occurs. Though it was clear the barring did not extend all the way up the back it was extremely difficult to assess the extent of it as the infrequent flight views usually involved birds passing overhead.
I have no knowledge of the range of plumage variation within nominate phaeopus but assumed it was probably extensive and mentally ‘put the bird aside’. The following day I noticed that one of the birds was darker and a richer brown in colouration to the extent that it was easy to distinguish regardless of range or light conditions. The photo below was taken at an uncomfortable range for my camera but this serves to illustrate the distinctiveness of the bird well (click on the image to enlarge).
It seemed likely that this dark individual was also the one showing an increased amount of barring on the rump and this indeed transpired to be the case. That evening I searched the internet and was pleased to find a plausible explanation quite quickly. It came in the form of a BBRC document which can be found here http://www.bbrc.org.uk/species-information-riact/waders which states that ‘Identification of variegatus is not straightforward as there is a cline in characters with nominate phaeopus, whilst young phaeopus can have more extensive dark markings on the rump than adults’.
I eventually managed to get two sets of shots which illustrate the rump pattern. The second set were taken at closer range and it was apparent that some of the markings on the rump were not discernable in the first. It is possible therefore that the image below may still not show the true pattern but remains the best I was able to secure. It can be seen that the barring on the tail is stronger and darker (what cannot be distinguished is the brown wash on the pale bars). It can also be seen that the barring extends further up the rump than on it does on the other bird in the frame.
A brief search of images on the internet e.g. http://www.wildbirdgallery.com/images/birds/numenius_phaeopus/variegatus.htm and the individual in the last photo on this page http://tsuru-bird.net/a_species/whimbrel/ would suggest that the Woolscott bird may not be entirely outside the limits for variegatus (perhaps at the western end of its range) but a 2cy phaeopus seemed a far more likely explanation so I set about searching for ageing characteristics. BWP didn’t help much (though currently I only have the concise version due to a crisis of shelving space) but yet again The Handbook of Bird Identification (for Europe and the Western Palearctic) came through with the goods. I had noticed that the inner primaries of the ‘dark individual’ were heavily notched (unlike those of the other birds) and thought this may be significant. It turns out that the juvenile is not only ‘warmer and buffer than the adult’ but shows ‘larger and more defined spotting and notching to wing feathers’. So, not a first for the UK in the Upper Leam Valley but an instructional individual (for me at least) and I put it ‘out there’ for the vanishingly small number of people I expect will be remotely interested. Another bird from the UK with extensive barring on the rump and some streaking on the upper back is documented here http://pewit.blogspot.co.uk/2009/09/whimbrel-variegatus.html.