Taxonomic status of 'Lesser Golden Plovers' Alan Knox n the past, there have been a number of suggestions that the two forms of Ithe Lesser Golden Plover, Pluvialis dominica dominica and P. d.Julva, might warrant separate specific status. The situation was unclear, mainly due to . Writ. Birds 80: 482-487, October 1987] 4oz Taxonomic status of 'Lesser Golden Plovers' 483 the lack of evidence from detailed field studies. That difficulty has been overcome to a large extent by several recent publications. After examining the evidence, the British Ornithologists' Union Records Committee has decided, on the recommendations of its taxonomic working group, to treat dominica and fulva as separate species (BOURC 1986). The English names suggested are American Golden Plover for P. dominica and Pacific Golden Plover for P. julva. In this paper, I shall review briefly the taxonomic problem, and outline the reasons for this change. Fig. 1. Distribution of Pacific Golden Plover Pluvialis fulva (stippled) and American Golden Plover P. dominica (vertical shading), both species breeding in the Arctic and wintering farther south Distribution The Pacific Golden Plover breeds on the tundras of northern Siberia, from the Yamal peninsula east to Chukotski, and across the Bering Strait in west and northwest Alaska. In the latter region, it overlaps with the American Golden Plover, whose range extends from northwest and north Alaska eastwards over arctic Canada to Baffin Island {fig. 1). Small numbers of dominica may breed in eastern Siberia, but proof of this is lacking, although specimens have been collected there during the nesting season. The evidence for breeding by dominica in Siberia was summarised by Portenko (1981), but with undue weight given to uncorroborated statements and inadequately documented records {see also Vaurie 1964). The two Lesser Golden Plovers are extreme long-distance migrants, travelling, in the case of fulva, to winter in northeast Africa, south and southeast Asia, the central and southwest Pacific islands, Australia, New Zealand and Polynesia. A few fulva now regularly winter in southern California. The American species undertakes a loop migration to winter mainly in south-central South America, from Bolivia and southern Brazil south to Patagonia. In wintcr,fulva is often found in coastal areas, whereas 484 Taxonomic status of 'Lesser Golden Plovers' dominica occurs largely away from the sea, on grassland and around inland waters. Taxonomy Several early workers in the Bering Strait area had noted the apparent overlap of the two Lesser Golden Plovers in Alaska and possibly eastern Siberia. With the similarity of appearance of the two forms, especially during the breeding season, it was difficult to determine to which taxon some of the birds should properly be allocated. The issue was further confused by reports of individuals with apparently intermediate characters. These were assumed to have been hybrids and it was argued, quite reasonably, that, if the forms were interbreeding with any regularity, they were better treated as subspecies. It is perhaps surprising that more attention was not paid at the time to the study by Conover (1945), since he showed that the two forms overlapped in Alaska without hybridising. The debate about intergradation continued, however (e.g. Gabrielson & Lincoln 1959). Recently, attention was drawn back to the subject by the decision of the Checklist Committee of the Ornithological Society of New Zealand to split dominica and Julva into separate species (OSNZ 1980). This was done on the basis of apparent differences in moult strategy and the time taken to reach maturity (Stresemann & Stresemann 1966), in addition to external appearance and migration pattern (Sibson 1977). The interpretation of some of these data has been controversial. The Stresemanns (1966, pages 53 & 200) did not actually look at the moult of dominica, only of Julva. They also quoted two authors who reported (immature)/«foa summering in the wintering areas. Subsequently, Kinsky 243. American Golden Plover Pluvialisdominica, Cornwall, September 1980 (W. R. Hirst) Taxonomic status of 'Lesser Golden Plovers' 485 & Yaldwyn (1981) found large numbers of immature/tt/wz on the wintering grounds in summer, lending support to the suggestion that julva did not return to their breeding habitats until IV2 or 2V2 years old, compared with dominica, which were said to return after six months. Observations by Johnson & Johnson (1983), however, differed in a number of respects from those of Kinsky & Yaldwyn. The Johnsons noted that first-year/ttfoa could be recognised in spring by their worn primaries, which were by then nine or ten months old. The adults, in contrast, moulted during winter, and had fresh, unworn primaries. Using these criteria to age Julva in Hawaii, they found that, although some young birds over-summered in the winter quarters, many did indeed return north. Johnson & Johnson were unable to substantiate a stay of up to 2V2 years in the winter quarters for 'most' Julva (contra Kinsky & Yaldwyn). Primary wear was also examined in Alaska, on specimens in breeding plumage (Connors 1983). As predicted by Johnson & Johnson, Connors found a large number of first-year Julva; in fact, his data suggested to him that many more Julva than dominica returned after one winter. This was in contradiction to the views of the Stresemanns. and Kinsky & Yaldwyn. Johnson (1985) was able to account for this discrepancy. He collected a small sample of migrant dominica in spring, and showed that birds aged internally as first-years had fresh primaries, as did the adults. Although most first-year dominica return north to Alaska in spring, they had not been recognised by Connors because of the differences in moult betweenjulva and dominica. Connors also examined birds collected in west and northwest Alaska and found sympatric* breeding of Julva and dominica in an area 1,300 km across. There were a few apparent intermediates, but he found the frequency of intermediate plumages in the area of sympatry to be no higher than in areas of allopatry* (Siberia; northeast Alaska together with Canada). On this 244. Pacific Golden Plover PluvialisJulva, USSR, September 1975 (Y. Shibnev) *A sympatric breeding area is one in which two or more different populations are found nesting alongside one another (in an area of sympatry). Where the populations do not overlap, they are said to be allopatric. For further information see Mayr (1969). 486 Taxonomic status of 'Lesser Golden Plovers' evidence, he recommended that the forms be treated as separate species. DeBenedictis (1984) argued against separation, saying that 'The main evidence, the scarcity of intermediates, would also be observed between subspecies which intergrade abruptly . and no samples come from the actual zone of intergradation.' Connors' data, however, clearly weigh against the existence of any hybrid zone. Indeed, they suggest that intermediates in the area of sympatry are not of hybrid origin. Since they are equally frequent in areas of allopatry, they are more likely to be part of the normal range of variation of the pure types. Furthermore, an area of sympatry 1,300 km across, running from almost pure dominica at one end to almost pure fulva at the other, would scarcely be called an abrupt inter­ gradation. The absence of samples from a short stretch in the centre of this zone is unlikely to affect Connors' conclusions. The differences between fulva and dominica in structure and plumage (Pym 1982; Connors 1983; Hayman et al. 1986), moult (Johnson 1985), migration pattern (no large-scale over-summering in the wintering areas has yet been reported for dominica), and lack of interbreeding in areas of sympatry (Conover 1945; Connors 1983) suggest that the two forms are better treated as separate species. Connors (1983) and Johnson (1985) have discussed the possible evolutionary history of the two taxa, and the selection pressures on them. The English names to be adopted by the BOU are those suggested by Connors (following Kinsky & Yaldwyn). They are in agreement with the 4th edition of the AOU checklist (1931), although the 6th edition (1983) uses Asiatic Golden Plover for fulva. 'Lesser Golden Plover' should be avoided, to remove confusion with the old name referring to both forms. The identification of the two species was discussed by Pym (1982, 1984) and, in greater detail, by Hayman et al. (1986). The status of the two forms in Britain and Ireland was reviewed by Pym (1982). Over 100 American Golden Plovers have been found here, mostly since 1966. In contrast, there are only a handful of records of Pacific Golden Plovers, the most recent being in Humberside in January-February 1985 (Brit. Birds 79: 544) and in Lincolnshire in July 1986 (Brit. Birds in press). Acknowledgments This paper is based on a report that was prepared for the BOURC. I am grateful to the other members of the Committee and Lars Svensson for comments at that stage. R. B. Sibson kindly sent me a copy of his note in Tara, which I was unable to locate in this country. I am also indebted to Iain Bishop, Robert Hudson and John Marchant for valuable comments on the manuscript. References AMERICAN ORNITHOLOGISTS' UNION (AOU). 1931'. Check-list of North American Birds. 4th edn. Lancaster, Pa. 1983. Check-list of North American Birds. 6th edn. Lawrence, Kansas. BRITISH ORNITHOLOGISTS' UNION RECORDS COMMITTEE (BOURC). 1986. Records Committee: twelfth report (April 1986). Ibis 128: 601-603. CONNORS, P. G. 1983. Taxonomy, distribution, and evolution of Golden Plovers (Pluvialis dominica and Pluvialis fulva). Auk 100: 607-620. CONOVER, B. 1945. The breeding Golden Plover of Alaska. Auk 62: 568-574. DEBENEDICTIS, P. A. 1984. Gleanings from the technical literature. Birding 16: 280-282. Taxonomic status of 'Lesser Golden Plovers' 487 GABRIELSON, I. N., & LINCOLN, F. C. 1959. The Birds of Alaska. Stackpole, Harrisburg. HAYMAN, P., MARCHANT, J., & PRATER, T.