Still exploring this subject…
This paper just published (authors inc, BF team member Andrea Corso) jam-packed with relevant feathers details.
A ‘wader-fest’ was what I had in mind for 20th July 2004 with fellow birder and BirdGuides doyen, Russell Slack. Unfortunately, Russ cried off at the last minute leaving me to peruse migrating shorebirds unaided. I arrived around 6:00 am at Paull Holme Strays (east of Hull in East Yorkshire on the Humber shore), which is an excellent shorebird hotspot. Among the dozen or so Curlew, I noticed one bird which was immediately paler looking with neat lines of pencil streaks along the breast and upper flanks. It caused me to wonder about the possibility of it being of the eastern taxon orientalis. I knew these were supposed to have gleaming white underwings, so when it took off and showed…gleaming white underwings, I was a bit bothered. Surely there had to be something wrong? Maybe it was a juvenile local Curlew. I had only had relatively brief views and with the tide coming in, I decided to head on to Spurn. I returned later in the afternoon when the tide had receded and relocated the bird in the same spot. Despite being a little distant in rather murky light I was able to get good views and take notes, as well as obtain a few photos over the next hour or so.
|Curlew: Paull Holme Strays, E. Yorks. Adult summer plumage showing features of the race orientalis (Photo: Martin Garner)||Curlew: Paull Holme Strays, E. Yorks. Adult summer plumage showing features of the race orientalis (Photo: Martin Garner)|
|Curlew: North Killingholme, Lincs. Adult summer plumage of the nominate race (Photo: Martin Garner)||Curlew: North Killingholme, Lincs. Adult summer plumage of the nominate race (Photo: Martin Garner)|
In summary, it was clearly paler overall, both on upperparts and underparts and at the longer-billed and longer-legged end of the Curlew spectrum. I reckoned it to be a tad longer-legged than most other Curlew present. The upperparts (whose detail I also studied later in the photographs) appeared to be an adult breeding pattern, with clear notching (holly leaf) on some scapulars and prominent pale and dark barring on the coverts. The coverts in particular had rather whitish fringing and were paler-looking than on other Curlew present. The underparts were even more striking with a pale buff ground colour to the upper-breast, ending in a vague pectoral band. The lower breast ground colour was white, as were the belly and undertail coverts…gleaming white. Overlaid on these, the breast and flanks were marked with neat thin pencil-line streaks. These were a little broader lower down (like a stretched teardrop) and on the area of flanks closest to the wing the streaking was slightly broader with a single line running at right angles to the dark shaft streak producing an ‘L’ shaped mark. There was however none of the heavier streaking, barring and arrowheads normally found on our Curlews in adult-type plumages. The belly was almost entirely plain and gleaming white and the flank streaking only extended down the legs and scarcely beyond. Again, most of the other Curlews were not so strikingly white, with a more extensive buff wash on the underparts with streaking being bolder and more extensive. The head pattern was paler and more open-faced with prominent whitish supercilium which looked unstreaked.
While variable 🙂 … more obvious example of orientalis shows this features in combination:
* overall paler than nominate arquatus * longer-billed and longer-legged * different pattern of fringing on coverts, lacking obvious cross barring * whiter underparts and cleaner white back and rump * outer primaries wholly dark on inner web (or almost) like Slender-billed Curlew * less and especially narrower dark bars on whiter tail * mostly/wholly white underwings (regular in Curlews in NW Europe) * tertials almost reaching primary tips
Several times the bird stretched its wings high, revealing what appeared to be wholly white underwing coverts and axillaries, the only exception being 2 or 3 thin brown bars traversing the feather near the tip of one of the axillaries. In flight it was also possible to see there was some wing moult taking place with the bird apparently missing one or two innermost primaries.
Overall, the combined pattern of upperparts, underparts, underwings, leg and bill length point to the possibility of the bird being a Curlew of the eastern race orientalis.
The orientalis race of Curlew is long overdue to be recorded in this country. It is a much longer distance migrant than our nominate birds, wintering as far west as the Gulf of Guinea in west Africa right down to South Africa. It is already well known from the eastern Mediterranean and BWP indicates that it appears to have been occurring increasingly westward in its migration strategy over the 20th century. The Curlew Sandpipers and Pectoral Sandpipers in the country on that day were probably from at least as far east. We are likely to get some pure and some intergraded type orientalis as indicated by BWP, and perhaps the 2-3 brown bars at the axillary tip may indicate this. I’m still left with some questions: I’d have liked a freeze-frame of the underwing, more flight views showing inner-wing and rump and tail pattern and the exact details of primary moult.
Postscript: A feature I have noticed subsequently and which I tentatively suggest as being helpful is that orientalis tend to have tertials which overlap most ot the primaries so the tip of the tertials can be almost as long as the primary tips. On nominate arquata Curlews, the tertials tips reach only as far as folded p8, thus well short of the tail tip. The tertial/tail tip/primary tip positions on the Paull bird are close to orientalis in arrangement on several photos.