Four Problem Stints

British Birds VOLUME 79 NUMBER 12 DECEMBER 1986 Four problem stints P.J. Grant his paper discusses four records of stints Calidris, the identification of T which has been much debated. All demonstrate the advances which have been made in recent years, especially including the publication of Lars Jonsson's stint paintings (Jonsson & Grant 1984). Reference to that paper will be useful when considering the records described here, as many of the identification points are illustrated and more fully described therein. Several important lessons can be learned from these case histories. The last three in particular demonstrate some of the major pitfalls and difficulties occasionally involved in stint identification, and the high degree of care necessary with some problem stints. Also well demonstrated is the importance to the identification process of good photographic evidence, and it is again urged that positive steps be taken to obtain a representative series of photographs (preferably colour transparencies) when a rare stint is suspected or identified. (Naturally, such steps should always have due regard for bird, habitat and other observers.) 1. Dungeness, Kent, 6th to 9th September 1965 The identity of this bird has been discussed in detail already (Brit. Birds 59: 543-547, plate 79; 72: 264-275, plates 127-129). It is again portrayed here (plate 306). It was originally identified as a Baird's Sandpiper C. bairdii, but [Brit. Birds 79: 609-621, December 1986] 609 610 Four problem stints 306. Juvenile stint Calidris (left), now identified as Little Stint C. minuta, with Dunlin C. alpina, Dungeness, Kent, September 1965 (Pamela Harrison). To facilitate easy comparisons, several photographs (this one and also plates 312, 317-319,321 & 323) have—at the specific request of the author—been reversed left to right, so that all the relevant birds are facing in the same direction 307. Juvenile Little Stint Calidris minuta, Kent, September 1979 (R.J. Chandler) iccepted by the British Birds Rarities Committee (BBRC) as a Semi- )almated Sandpiper C. pusilla (59: 289). This decision was withdrawn in 979, when it was described as 'probably either Little C. minuta or Red- lecked Stint C. ruficollis' (72: 266). The fact that it can now be firmly dentified as a juvenile Little Stint (and that any 'lurking doubts' that it Four problem stints 611 may have been a juvenile Red-necked can be dismissed) is clear evidence of recent advances, especially in the identification of the previously little- known Red-necked. Identification of this individual is now actually rather straightforward. It shows the classic features of a juvenile Little: 1. Fine-tipped bill with very slightly decurved lower mandible (bill of Red-necked averages shorter, straighter and blunter-tipped). 2. Prominent split-supercilium and dark central 'ridge' on crown (whole crown of Red-necked usually rather uniform). 3. Obvious white mantle V (usually faint or lacking on Red-necked). 4. All scapulars, wing-coverts and tertials 'matching', showing blackish centres and neat pale fringes (on Red-necked, only the upper scapulars have blackish centres, and there is thus contrast between these feathers and the plainer, greyer lower scapulars, wing-coverts and tertials). 5. Dark streaking on the breast-side forms an isolated patch (streaking on Red-necked more extensive and more diffuse). 6. Shape normal for Little Stint, lacking typical Red-necked's long-bodied, short-legged outline. Semipalmated Sandpiper was also excluded for similar reasons, and one photograph clearly showed unwebbed toes, as previously noted (72: 265). 2. Covenham Reservoir, Lincolnshire, 7th to 19th September 1974 This previously unidentified and very 'different-looking' stint (plates 308 & 309) has, not surprisingly, prompted much speculation. In 1979, it was reported to have 'provoked a range of opinions' within the BBRC, and was labelled 'stint, perhaps Red-necked, but identity still uncertain' (72: 264- 274, plates 141-143). Judging only by its plumage features, it is clearly another juvenile Little and certainly not Red-necked: it has all the classic features, as described above for the Dungeness individual, and colour photographs also show very strong rufous fringes on the tertials and wing- coverts which Red-necked would never show in such strength of colour. Again, better knowledge, especially of juvenile Red-necked, is the key to this identification. 308. Juvenile stint Calidris, now identified as Little Stint C. minuta, Covenham Reservoir, Lincolnshire, September 1974 (Keith Atkin) [The inclusion of colour plates 308-321 has been subsidised by ZEISS West Germany. EDS] 612 Four problem stints 309. Juvenile stint Calidris, now identified as Little Stint C. minuta, Covenham Reservoir, Lincolnshire, September 1974 (Keith Atkin) 310. Juvenile Red-necked Stint Calidris ruficollis, Japan, September 1983 (T. Shiota) In other ways, however, this bird is undeniably odd. The bill is long and rather straight (nonetheless still closer in shape to Little than to Red necked), and the body looks peculiarly long. Unlike normal Little Stints, its tail projected slightly beyond the wing-tip, and careful field observations over long periods clearly showed that it was 10-15% larger than accompanying Little Stints (K. Atkin in litt.), although 'size-illusion' may have exaggerated its large size in some photographs, as discussed Four problem stints 613 311. Juvenile Little Stint Calidris minuta, Alaska, USA, September 1983 (GeraldMaisel) previously (76: 327-334; 77: 323-325). It fed steadily, without the usual dashing activity of Little Stint, and its call was lower-pitched and slightly slurred compared with Little's usual high-pitched, sharp 'stit' note (K. Atkin in litt.). It was probably just an extremely large, long-billed female Little Stint, but there remains a possibility of some other explanation for its unusual appearance. 3. Fair Isle, Shetland, 11th to 13th August 1982 This remarkable-looking 'stint' in worn adult-summer plumage (plates 312-315) was submitted to the BBRC as Britain and Ireland's first Red necked Stint. On its first circulation, it was unanimously accepted, although seven of BBRC's ten members called for a confirmatory check of this little-known plumage against museum specimens or by an independent expert. Accordingly, the descriptions and the two photographs then available to the BBRC (plates 312 & 313) were sent for comment to Lars Jonsson, who was then working on the illustrations for the forthcoming stint identification paper. His opinion, later unanimously endorsed by the observers and the BBRC, was stunning: not a stint at all, but a Sanderling C. alba\ The following is a summary of the main pro-Sanderling points from Lars Jonsson's very thorough analysis: 1. Whitish area on ear-coverts below eye (never shown by Red-necked). 2. Colour on chin, throat and ear-coverts (at least in the photographs) rather too orange- toned (not the 'brick-red' of classic Red-necked). 3. Fine, dark streaking on throat and ear-coverts (always unmarked, uniform brick-red on Red-necked). 4. Mantle and scapulars strongly chequered black-and-white (Red-necked has white-fringed upperparts feathers in fresh summer plumage after the spring moult, but these fringes quickly disappear through wear: in moderately-worn summer plumage, upperparts of Red-necked would be strongly rufous-fringed). Four problem stints 615 314 & 315. Adult summer Sanderling Calidris alba, originally identified as Red-necked Stint C. ruficollis, Fair Isle, August 1982 (James Dickson) 6. The dark marks on the breast-side have some orange tones intermixed (breast-side basically white on Red-necked). 7. Some of the breast-side markings are fine, wavy bars (always sharp streaks or arrowhead- shaped marks on Red-necked, never bars). 8. The bill is rather too large and stout for a Red-necked. 9. The moult of the primaries (evident from the primary shaft visible in some photographs) is more advanced than would be expected for Red-necked (according to BWP vol. 3, earliest primary moult is August-December), but fits Sanderling (earliest, end July-late October). 616 Four problem stints Some other considerations are important. One photograph (not included here) clearly shows that the bird has no hind toe, a unique feature of Sanderling amongst the small sandpipers. The bird frequented Fair Isle's stony, short-grassed airstrip, rather unusual habitat for a Sanderling in most parts of Britain (but normal in its breeding areas) and was thus 'out-of-context' to observers familiar with its normal wave-chasing behaviour. It was undoubtedly a small individual (size estimated in the field as about that of a Wheatear Oenanthe oenanthe or about 75% that of Ringed Plover Charadrius hiaticula which were alongside), but it should be noted that the largest Red-necked in BWP vol. 3 has a wing-length of 112 mm, only about 7% smaller than the smallest Sanderling at 120 mm, which could thus easily be mistaken for 'stint-sized' without direct comparison. Worn adult-summer plumage of Sanderling is not a familiar plumage to most observers in Britain, and is quite different from the more familiar fresh summer-plumage of spring migrants (but which provides its own particular pitfalls when out of usual Sanderling habitat). Wear and wing-moult would have reduced the strength of the usually broad, white wing-bar, normally an easy mark of Sanderling. Finally, the call, noted as a quiet 'swit', is compatible with the usual 'twik' of Sanderling. This experience draws attention to the major pitfall in the identification of an adult summer Red-necked Stint: an out-of-context Sanderling in worn summer plumage. Claudia Wilds (in litt.) has pointed out that a less orange (female?) worn adult-summer Sanderling could also be mistaken for a Semipalmated Sandpiper in summer plumage. 316. Adult summer Red-necked Sdnt Calidris ruficollis, Alaska, USA, June 1985 (Jon Dunn) Four problem stints 617 4.

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