The juvenile plumage of the Icelandic Black-tailed Godwit and further occurrences of this race in England

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1 The juvenile plumage of the Icelandic Black-tailed Godwit and further occurrences of this race in England By James M, and Jeffery G. Harrison (Plates 6-7) VERNON (1963) FOCUSED attention on the occurrence of the Icelandic Black-tailed Godwit ~Limosa limosa islandica in Britain and, quoting Williamson and Ruttledge (1958) in support, indicated that this form appeared to favour the 'western and southern half of the country. This opinion was also upheld by Norrevang (1959) and by Boyd (1962) who believed that tne majority of the Black-tailed Godwits wintering in the British Isles belonged to this race. On the European Continent, single specimens of islandica have been identified from continued... 10

2 ICELANDIC BLACK-TAILED GODWITS IN ENGLAND western France (Havre), Belgium (Dunkerque), Holland (Friesland) and Spain (Andalucia), while birds from Norway in both spring and autumn have been assigned to this race by Holgerson and Willgohs (1956). There are no records from Denmark. Ash (1964) examined a number of Black-tailed Godwits found dead in Hampshire and Dorset in the severe winter of 1962/63. Of 19 specimens, he determined twelve on measurement as islandka; of the rest, two were probably islandka, two were intermediate and three which had been damaged by predators were unsuitable as comparative material. In view of these observations, the writers re-examined all the specimens in their collections. It became apparent that the juveniles could be divided into two distinct groups on colour and pattern, one group being assigned to the Icelandic race on measurements. We therefore studied further comparative material, consisting of a pair of breeding islandka and a full-grown juvenile from Dr. Finnur Gudmundsson; five nominate birds and one islandka from Holland; five nominate birds from north-west Germany in J.G.H.'s collection; and 11 nominate and 16 islandka in the British Museum. Vernon stated that islandka could be identified by 'their shorter bills (sex for sex) and by their redder plumage in the breeding season', to which must be added that the plumage on the upper-parts is much fuller and on the under-parts more heavily barred. We have found that the colour distinction also holds good for the Table 1. Colour comparisons of Continental Black-tailed Godwits Limosa I. limosa and Icelandic Black-tailed Godwits "Limosa I. islandka The colours given are those in Maerz and Paul (1950), the figures in brackets showing the number of the plate concerned and the number of the colour on that plate LIMOSA ISLANDICA Adult 6* Hindneck Foreneck Breast Adult $ Hindneck Foreneck Breast Juvenile Hindneck Foreneck Breast Rose beige (5, 10 A) Rose beige (5, 10 A) Rose beige (5, 10 A) nearest to Long ; Beach+(12, 4A) Moonmist(iz.,2A) Parchment (12,3B) Ferruginous (5, 12D) Burnt sienna (5, 12F) Feuille morte (5, 12A) Spice (13, 12D) Bombay (14, 12H) Feuille morte (5, 12A) nearest to Longchamps (5, 9A) slightly yellower than Airedale (14, 6F) II

3 BRITISH BIRDS juvenile plumage. In fact the two races have to be matched from two quite different colour ranges in A Dictionary of Color (Maerz and Paul 1950). In order to define this, we made colour comparisons of the hindneck, the foreneck and the breast in the two races and the results are given in table 1. The far richer chestnut colour of the juvenile islandica can be seen well even in the black-and-white photographs on plates 6 and 7, particularly in the case of the upper-parts (plate 6). But it is not just a matter of intensity of colour, for the pattern is far more striking not only in the adult islandica but also on the upper-parts of the juvenile. There is little doubt that, for anyone familiar with both races in the museum, there are sufficient differences in the juvenile to enable it to be recognised under good visual conditions in the field. In this respect there is a close similarity between the Icelandic Black-tailed Godwit and the Iceland Redshank Tringa totanus robusta, for the latter also has a fuller and more contrasted summer plumage than the more southerly races (Harrison 1944). These differences in colour and pattern help to resolve the problem of the intermediate specimen, for it is recognised that there is some overlap in the measurements that separate the two races. Furthermore, in the case of the juvenile, it enables one to establish an accurate identification in specimens where the bill may not as yet be fully grown. The 18 specimens listed in table 2 are ones in our collections which Table 2. Specimens of the Icelandic Black-tailed Godwit Limosa limosa islandica in the authors' collections identified on bill measurements and plumage characteristics Date Locality Age/sex Bill (mm.) Brookland, Kent near Canterbury, Kent Tetney, Lincolnshire Ringwood, Hampshire near Sandwich, Kent near Sandwich, Kent North Kent Medway Estuary, Kent Juv. unsexed Juv. (J istw. S Unsexed Juv.? Ad. S Juv. unsexed i

4 ICELANDIC BLACK-TAILED GODWITS IN ENGLAND we have identified as islandica on both bill and plumage. They include 16 from Kent, one from Lincolnshire and one from Hampshire, the last having come from a wintering flock of 150. It is noteworthy that we have only five specimens from Britain which can be assigned to the typical race ~Limosa limosa limosa; all are from Kent. It would seem from table 2 that the Icelandic race is a frequent passage migrant in Kent and here again there is a close parallel with the Icelandic Redshank, which Harrison (1953) has shown to visit the county in appreciable numbers (though in winter as well as on passage). The North Sea would seem to be a dividing line between the two races, both on passage and in winter. The nominate race appears to be rather less frequent in Britain than was formerly thought. In this respect, one might wonder which race it is which has returned to breed in England. We have been able to examine a colour transparency taken by Dr. C. D. T. Minton of a juvenile which he caught on 20th August i960, one of seven which had been in that particular locality since the end of July and which Dr. Minton believes were locally bred. There is no doubt that the bird in question is a good example of islandica on plumage characters and, although no measurements were taken, the bill looks relatively short. Although in a scientific sense this is no proof that islandica is the breeding race in England, it is nevertheless suggestive. Occasional breeding birds in northern Scotland have been assumed to be Icelandic, but it might seem surprising that this race should also nest in England. It might be thought that habitat requirements would be different for the two races, but we have seen both on their breeding grounds and the long grasses of the glacio-fiuvial plains of south-west Iceland are little different from the lush fresh marshes of north-west Continental Europe. In studying the races of the Redshank, Harrison (1944) showed that the British race britannica is more closely related to the Icelandic robusta than to the typical race on the Continent. In our opinion, therefore, it is quite possible that the Icelandic Black-tailed Godwit is the race which has returned to nest in England and, especially considering its prevalence on migration and in winter, this may not be so surprising after all. ACKNOWLEDGEMENTS We are very grateful to J. D. Macdonald of the British Museum (Natural History), Dr. Finnur Gudmundsson of the Natural History Museum, Reykjavik, Iceland, and Dr. G. F. Mees of the Natural History Museum, Leiden, Holland, for the loan of specimens and to C. W, Mackworth-Praed for the gift of the Icelandic Black-tailed Godwit from Hampshire. We are also indebted to Professor K. H. Voous for his assistance, to Dr. C. D. T. Minton for the loan of the 13

5 BRITISH BIRDS colour slide and details of the probable English-bred juvenile and to Dr. Pamela Harrison for the photographs of the specimens on plates 6 and 7. SUMMARY Juveniles of the Icelandic Black-tailed Godwit IJmosa limosa islandka are shown to be recognisable not only on measurement, but also on colour and pattern. A further 16 specimens are listed from Kent and one each from Lincolnshire and Hampshire. It is suggested that the nominate race L. /. limosa is less frequent in Britain than -was formerly supposed and the possibility is discussed that the population which now breeds in England belongs to the Icelandic race. REFERENCES ASH, J. S. (1964): 'Observations in Hampshire and Dorset during the 1965 cold spell*. Brit. Birds, 57: BOYD, H. (1962): 'Mortality and fertility of European Charadrii'. Ibis, 104: HARRISON, J. M. (1944): 'Some remarks upon the Western Palaearctic races of Tringa totanus (Linnaeus)'. Ibis, 86: (195 3): The Birds of Kent, London. HOLGBRSON, H,, and WILLGOHS, J. F. (1956): 'First breeding of the Black-tailed Godwit Limosa limosa (L.) in Norway'. Astarte, 13: 1-8. MAERZ, A., and PAUL, M. R. (1950): A Dictionary of Color. 2nd edition. NORREVANG, A. (1959): 'The migration patterns of some waders in Europe, based on the ringing results'. Vidensk. Medd. Dansk Naturb. Form. Kbh., 121: VERNON, J. D. R. (1963): 'Icelandic Black-tailed Godwits in the British Isles'. Brit. Birds, 56: WILLIAMSON, K., and RUTTLEDGE, R. F. (1957): 'Icelandic Black-tailed Godwits wintering in Ireland'. Brit. Birds, 50:

6 PLATES 6 and 7. Skins of Black-tailed Godwits Limosa limosa to show plumage distinctions of Icelandic and Continental races. Left to right in each case: (1) juvenile 9 ishndica, Iceland, August 1958; (2) juvenile $ Umosa, Belgium, August

7 1916; (3) adult tyjslandica, Iceland, May 1957; (4) adult 6* limosa, Germany, April The richer plumage of islandica, in particular on the juvenile upper-parts, can be seen even in black-and-white photos (pages 10-14) (photos: Pamela Harrison)