From the Lothian Bird Report for 1997.
Any thoughts of completing my WeBS count were soon abandoned when I picked up a small, grey and white wader on the Musselburgh wader scrape at 8.15 a.m. on 9th August 1997. The bird was feeding with 175 Dunlin and immediately stood out as being stint-sized, uniform grey above and white below with a longish, slightly decurved bill. Nobody else arrived before it flew off to the River Esk mouth as the tide receded, but fortunately it had approached close enough for me to get enough detail to check some field guides back home - Western Sandpiper, Semipalmated Sandpiper or an odd Little Stint were the choices, in that order of preference. The initial excitement of finding this bird was followed by a long and sometimes onerous and difficult process of identification, spreading the news on grapevines and writing up the description - a process that was to disrupt family life for over a month.
It failed to reappear on the scrape on the evening and following morning's tides, but luckily Dave Allan picked it up roosting on the westernmost ash lagoon. Indeed it transpired that a pale stint had been present on the roost since 25 July (originally with a summer-plumaged Little Stint) and I appear to have seen it on its only visit to the scrape. A group of us finally got close views on Fisherrow Sands (at the end of Mountjoy Terrace) and after much deliberation it was decided to put it out as a probable Semipalmated, largely on the basis that this would encourage others to come and see it, but prevent a major panic. In any case, the bird's build and buffish grey upperparts tended to support this ID.
The stint's routine of roosting on the ash lagoon and feeding on Fisherrow Sands, where it was more approachable, enabled many birders to see and photograph it. However, not surprisingly opinions varied as to its identity. On seeing Gary Bellingham's excellent photos, taken in thick fog on 11th, I guessed that these were going to be the key to its identification - a view also held by Killian Mullarney who I showed a single photo at the Rutland Water Bird Fair. The routine of the bird, now considered to be a Western Sandpiper, changed on 19th, when it failed to appear at Musselburgh. On the following two days (of spring tides) it showed only at low tide, but as a lot of waders commute the 14 km to Aberlady Bay to roost, it was no surprise when Iain Thomson found it roosting there on 21st and 22nd.
On the weekend of the English August Bank Holiday an estimated 2000 people saw the beast, some making a 1000-mile round trip from the south coast. However, the bird decided to lead many a merry dance. On Saturday (23rd) it failed to show at Aberlady and returned to Musselburgh for the day. On Sunday (24th) it was back at Aberlady on the early tide, but was flushed by a Peregrine. It was relocated at Gosford Bay mid afternoon but was back at Aberlady for the high tide roost. On Monday (25th), it again returned to Musselburgh for its final day's appearance.
Identification
As is the case for many stints or peeps, identification was far from straightforward especially as this bird was in a nondescript winter plumage. I have little experience of American peeps and, as I later discovered even for those with experience, the separation of Western Sandpiper from the closely related Semipalmated Sandpiper, is not easy. Considerable detail had to be noted, a process which was made so much easier by having good quality, close-up pictures to hand (see Acknowledgements).
Head pattern, bill shape, overall jizz, scapular/mantle colour and pattern and moult were key features in the identification of this bird.
Its size was estimated to be c.20% smaller than Dunlin, but judged to be not as small and compact as Little Stint. On first glance, it appeared uniform pale grey above, and white below with a bill that was rather longer than that of a Little Stint (more details below). The jizz of the bird was rather variable. In general and at a distance, it looked short necked and rather dumpy, but with longish legs set back of centre. Other times it looked more like a small Dunlin than a stint, perhaps because of its long bill, long legs and at times rather angular contours. Killian Mullarney commented on its front-heavy and rather angular appearance based on the photographs.
On the scrape it fed in shallow water and on mud with the Dunlin, however it kept to the shallowest water and didn't go in up to its belly as did the Dunlin. Its feeding action on the scrape was rather like a Dunlin-walking and probing, not running and prodding on the muddy edges like a Little Stint. On the foreshore, it fed in a similar deliberate way with a rather plover-like walk-and-probe action - walking with jerky head movements and deliberate quick probes before walking on for a short distance.
The overall colour of the upperparts was mousy grey; not totally cold grey, but with a distinct hint of buff especially in dull light. In bright sunshine, it appeared more grey and white. Most of the visible upperpart feathers (scapulars) were buffish grey with a thin dark shaft line and very thin white edging (slightly broader at the tip). Two outer scapulars showed a darker centre to the feather and the lowest of the upper line of scapulars also had darker centres. However, these were not considered to be summer plumage feathers. The tertials were also a slightly darker brownish grey with thin pale edgings. The wing coverts were moulted and fresh. Photos also revealed two small scapulars in the upper row closest to the mantle which are marginally richer brown, but with the same overall pattern.
The underparts were pure white with the only markings being on the sides of the breast. These breast patches consisted of a relatively small area of short dark streaks on a pale wash. In the field they were apparently restricted to the sides, but on photos a line of very short, barely-visible streaks could be discerned extending between the breast patches.
Wing length versus tail and tertials. For most of the time it was impossible to see any primaries projecting beyond the long tertials, but on a few occasions c.1 mm of the primary tips could be see. The tail was about 1 mm longer than the wing.
The crown was well marked with a dense pattern of fine, dark streaks on a grey background. The forehead had finer streaking. The nape and upper back were also streaked but with finer streaks resulting in a paler hue, contrasting with the scapulars and wings. The pale supercilium in front of eye joined over the bill to form a pure white strip above the bill. There was no white above the eye itself, with the crown streaking extending down. No eye ring was visible in the field. There was a prominent supercilium behind the eye-this was broad, pale and flared up at the rear. The lores were darker. The upper ear-coverts had dark streaks as crown, but became less on lower ear-coverts. A clear feature of the head was the 'bow tie' effect formed by the flared supercilium behind the eye and the pale area above the lores in front of the eye.
The bill was black, rather long (longer than typical Little Stint and some 2/3 that of Dunlin) and was straight except that the distal 1/3 was slightly decurved. It was deeper at the base and tapered, but generally rather thin and not broad-based and chunky as in Semipalmated. Where the bill became decurved there was also a slight thinning of the bill. In photos, the lore:bill ratio was measured as 1:2.6 to 2.8, confirming the 1:2.5 estimated in the field. A slight terminal thickening was noticed only at very close range with the bird face on and the bill against the white chest. It was not at all obvious and was considered to be no more than any stint would have. This would be an exceptional bill for any Semipalmated, even a long-billed female. For a Western, the Musselburgh bird's was at the short end of the range.
The legs were black and longer than those of Little Stint, especially below the knee. Several birders saw the partial webbing between the toes at a range of 5 m, and Colin Davison remarked that at close range and against sand the webbing was very obvious-more so than on a comparable Semipalmated he had seen.
A single call was heard by Chris McGuigan when he was very close to the bird. It uttered a very quiet, high-pitched, short, monosyllabic, lispy 'psit'.
Moult
The bird was clearly in an advanced stage of moult into winter plumage having moulted its wing coverts, scapulars, inner seven primaries and outermost secondary. Only three old primaries, the longest ones, remained and one primary (P7) was still growing; the outermost secondary (S1) was also still growing. The primary coverts were correspondingly new except for the outer two or three. The rather haphazard arrangement of scapulars suggested that some of these feathers were also still growing. The greater wing coverts were fresh, except for one (presumed innermost greater covert) which was pale-edged.
Early moult. Semipalmated moult considerably later than Westerns and most (if not all) vagrant adults show signs of summer scapulars and have abraded wing coverts. Although only an indicator, this feature alone was considered to strongly suggest Western. The question of it being a 1st-summer bird, which would moult earlier, is more open to question, but it is suggested that even this would show one or two dark-centred, summer scapulars.
Age
The bird was in non-breeding plumage, and either a 1st-summer or an adult virtually moulted into winter plumage. Perhaps the moult has progressed so far that it is justified to call it simply an adult in winter plumage.
Status
Western Sandpipers breed on the tundra of far north-eastern Siberia and northern Alaska and winter mainly in southern USA, West Indies, Central America and Southern America. They migrate mainly down the Pacific coasts of Canada and the USA, and only use the Atlantic coast south of Massachusetts (they are very rare in eastern Canada).
There were only two previous records of Western Sandpiper in Scotland (1956 and 1988) and these were both on the Northern Isles. It was therefore a first for Lothian, indeed a first for the Scottish mainland, and only the sixth for Britain. As an aside, it is interesting to note the far higher ratio of Western to Semipalmated in Scotland compared with south of the border.
Acknowledgements
I must thank Gary Bellingham and Dr Iain H. Leach for their invaluable photographs, and also Killian Mullarney for his informed opinion on the bird's identification. Without the combined input of these individuals I have no doubt that the bird would have caused many more headaches than it already has.
Ian J. Andrews, 39 Clayknowes Drive, Musselburgh, Midlothian EH21 6UW