British Birds - Back Issues 2000

Identification, taxonomy and distribution of Greater and Lesser Sand Plovers Erik Hirschfeld, C. S. (Kees) Roselaar and Hadoram Shirihai

Separating Greater Charadrius leschenaultii and Lesser Sand Plovers C. mongolus is far from simple, especially since the various subspecies of the two show some overlap in morphology and biometrics (as well as geographical distribution). On the basis of extensive field observations and detailed examination of about 300 museum specimens of each species, identification criteria are presented. Important characters are considered to be bill shape, length of bill nail, wing-bar shape, prominence of subterminal tail-bar and (in breeding plumage) shape of breast-band; other supporting or inconclusive characters are also discussed. A major pitfall is that the small race columbinus of Greater has a bill closely approaching that of Lesser, although never so blunt-tipped as on any race of the latter. For both species, populations are placed into geographical groups according to biometrics: from these data, supported where possible by other factors, subspecies are defined. Three races of Greater are recognised: nominate leschenaultii, columbinus and crassirostris. Five subspecies of Lesser are recognised: nominate mongolus and stegmanni (the ‘mongolus group’), and pamirensis, atrifrons and schaeferi (the ‘atrifrons group’, possibly an incipient separate species). Even in breeding plumage, subspecific identification of Lesser Sand Plover requires great caution, as wide variation occurs within populations and intermediates are frequent. Identification of juveniles and non-breeding adults is possible only with careful and precise assessment of structure, ‘jizz’, and upperwing and uppertail patterns. Greater (especially columbinus) has an earlier post-breeding (and pre-breeding) moult than Lesser, which does not moult until arrival on winter grounds. In Europe, a vagrant sand plover in full or nearly full summer plumage after mid August is likely to be a Lesser, as also are a small mongolus/columbinus-type in breeding plumage in July or early August and a small individual in active wing moult after September; by contrast, a small sand plover in full summer plumage in February or March is likely to be a columbinus Greater, as is a juvenile appearing in western Europe in June or early July. From this study and existing literature, the global breeding distributions of each species and its subspecies are reassessed. A tentative picture of winter distributions of all races is drawn up, based on biometrics and to some extent on plumage darkness. Of particular note is the fact that western populations of nominate Greater appear to migrate at least partly southwest rather than southeast, and that a possible breeding population of Greater (resembling columbinus, but shorter-winged) exists along the Red Sea.

Marbled Murrelet in Switzerland: a Pacific Ocean auk new to the Western Palearctic Lionel Maumary and Peter Knaus

Between 15th and 18th December 1997, a first-winter Marbled Murrelet Brachyramphus marmoratus of the Asian subspecies perdix was discovered dead in a fishing net at Zollikon, Lake Zurich, Switzerland. It constitutes the first record of this Pacific Ocean species for the Western Palearctic, accepted by the Swiss Rarities Committee as relating to a wild bird and placed in Category A. The circumstances of the finding and identification of the specimen are described, and an updated overview of the conservation status in the breeding range and of the taxonomy of this little-known, threatened auk is provided