SIBERIAN THRUSH ON THE ISLE OF MAY: A NEW BRITISH BIRD By D. G. ANDREW, J. A. NELDER and MARY HAWKES ON 2nd October 1954 an adult male Siberian Thrush (Turdus sibiricus) was trapped on the Isle of May. It had been glimpsed, but not positively identified, shortly before dusk on the previous day and was still present on the island when we left on the 4th. It had gone by the 7th. Two photographs of the bird, taken while it was being examined in the hand, are reproduced' on plate 7. The following notes are based on the detailed description taken down at the time. The general body colour was slate-black, against which the long, pure white eye-stripe stood out in brilliant contrast. The feathers on the centre of the belly and the under tail-coverts were broadly tipped off-white, but in the case of the under tail-coverts these whitish tips were not long enough to cover the blackish bases of the feathers and the resulting pattern was one of alternating black and white crescents. The general colour of the wings was again slate-black with blackish flight-feathers. The complex pattern on the underwing can be seen in the lower photograph on plate 7. The rectangular white panels on the inner webs of the primaries and secondaries (absent on the four innermost secondaries and decreasing in extent on the outer primaries until practically non-existent on the second primary) combined with the white tips of the under greater coverts to form a broad white band running almost the whole length of the under-wing. A narrower, shorter band at the base of the wing was formed by the white bases of the under median coverts and the white tips of the under lesser coverts. The tail had 12 rectrices, the feathers ending in a fine spike at the tip. The two central pairs were blackish: the remainder, with the exception of the outer pair, were blackish with small pure white wedges at the tips which were most extensive on the outer feathers. The outer pair were sooty, with the outer web narrowly tipped white as in the other feathers but with the inner web broadly tipped' off-white. This feature can be seen in the upper photograph on plate 7 where the left hand outer tail-feather has been turned out of position to show the pattern. Measurements and structure: wing 125 mm. ; tarsus 30-31 mm.; bill: upper mandible 21 mm., lower mandible 5mm. shorter. The lower mandible had been broken off just short of the tip and the upper mandible had grown over this and was strongly decurved at the tip (just apparent in plate 7, upper). The weight when trapped about midday on 2nd October was 59.7 gm. It was retrapped first thing next morning when it weighed 61.6 gm. The 21
22 BRITISH BIRDS [VOL. XLVIH top of the skull was noticeably flat and' lacking in "forehead", giving the bird's head a much less rounded outline than is shown in the illustration in A Field Guide to the Birds of Britain and Europe, p. 222. Soft parts: Gape orange-yellow; bill black, except for tip of upper and base of lower mandible which were horn; legs and feet front of legs and top of toes purplish horn, back of legs, soles and joints dirty yellow; iris dark brown. Field-characters: In stance, build and behaviour the bird was a typical thrush. In behaviour it most resembled a Blackbird (Turdus merula), tending to skulk under huts and other cover. It was not unduly shy. The white on the under-parts hardly showed up at all in the side view, and the bird appeared almost uniform slate-black with a pronounced bluish tinge except for a paler patch on the flanks (caused by white shafts to the flank feathers) and an appreciably darker colour on the head (caused by black centres to the crown feathers). Viewed from the front, the white belly merely showed up as a narrow whitish stripe between the legs. The white eye-stripe was always a most conspicuous feature. In flight the white tips to the tail-feathers showed up most strikingly as a row of disjoined white spots. The white band along the underwing immediately caught the eye and, when the wing was fully extended, we also had the impression of a narrower white line along the upper surface of the wing. The bird fed normally in spite of its deformed bill. The only call-notes heard were a gruff squawk when suddenly flushed at close quarters and a short "zit", very much like that of a Song Thrush (Turdus philomelos) but softer and perhaps purer, but it was a rather silent bird. The arrival of this bird on the island coincided with a brief spell of south-east wind and drizzle which started during the night September 30th-October 1st and continued for most of the following day. Some Gold'crests (Regulus regulus) (apparently of the Continental race) came in during the small hours of the morning, but otherwise there was no sign of immigration until midday, when the first Redwings (Turdus musicus) of the autumn began to be seen (those trapped were of the Continental race, T. m. musicus). By the end of the day about 75 of these birds were on the island but the only other arrivals were a Pied Flycatcher (Muscicapa hypoleuca), at least 3 Brarnblings (Fringilla montifringilla) and a Reed Bunting (Emberiza schoeniclus), and it is rather remarkable that such a small-scale influx should have brought with it a migrant from Siberia. An examination of the synoptic charts for September 1954 casts little light on the wanderings of this bird. Throughout the month pressure was generally high over south-east Europe and south Russia, with light winds, while a continuous stream of depressions passed eastwards across the Atlantic, then north-east across Europe. The south-east wind which brought this bird to
VOL. XLVIII] SIBEEIAN THRUSH ON THE MAY 23 the island was localised over the northern North Sea and the east coast of Britain, suggesting - a Scandinavian starting point for the flight across the North Sea, but the meteorological situation further east at that time does not allow any obvious interpretation of the bird's movements. THE WORLD DISTRIBUTION OF THE SIBERIAN THRUSH (Turdus sibiricus) (Compiled and drawn by Holger Holgersen) The breeding range is indicated by the darker, cross-hatched area, the winterquarters by the lighter, stippled portion. The various European records are shown by dots. The typical race of the Siberian Thrush, Turdus s. sibiricus, breeds in central Siberia. The breeding range of the species extends eastwards to Japan; Japanese birds are separated as Turdus s, davisoni, and are characterised in the male, among other things, by a near or total absence of white on the belly and under tail-coverts. It is worth mentioning perhaps that the amount of white on the tail of the bird caught on the Isle of May was greater than that on most, it not all, the adult male skins examined at the British Museum. The species winters in south-east Asia. We are very grateful to Dr. Holger Holgersen for allowing us to reproduce here his map of the distribution of the Siberian Thrush which
24 BRITISH BIRDS [VOL. XLVIII originally appeared in Stavanger Museums Arbok 1953, p. 104. In spite of the remoteness of its breeding grounds, this species has been recorded in most European countries and its appearance in Britain is not therefore very surprising, [The Siberian Thrush may now certainly be regarded as a British bird, but this is not the first occasion on which the question of its occurrence in this country has been raised. Two previous records, neither of which has received universal recognition, are mentioned in various published works, including The Handbook (Vol. II, p 141). Their rejection seems to date from the time of Howard Saunders who said in the revised (1899) edition of his An Illustrated Manual of British Birds : "An example of the Siberian Thrush (T. sibiricus, Pallas), said to have been shot in Surrey in the winter of 1860-61, and originally supposed to be a melanism of the Redwing, was in the collection of the late Mr. F. Bond, who bequeathed it to the British Museum; while I fully believe that another was picked up exhausted at Bonchurch, I of Wight, in the winter of 1874; but the evidence is as yet not sufficient to warrant the introduction of this species into the British list." Substantially the same account appeared in the 1st edition (1889). The second part of this statement has been much quoted, usually without comment, and in this way it appears in The Birds of Hampshire and the Isle of Wight (1905) by J. A. Kelsall and P. W. Munn, but we have been able to trace no further evidence and the record can therefore at this time be safely ignored. The Surrey bird, on the other hand, has a wealth of supporting information as the following account from J. A. Bucknill's Birds of Surrey (1900), pp. 15-16, shows: "The only example of this Asiatic species which has been definitely recorded in this country up till March, 1899 (though Mr. Howard Saunders, in his Manual of British Birds, p. 12, mentions another possible example from the Isle of Wight, 1874) is a bird which is said (fide Mr. Harting, who was told by Mr. Bond) to have been shot in Surrey between Guildford and Godalming in the winter of 1860-61. It was sold to, and was for many years in the collection of, the late Mr. Frederick Bond (perhaps the best known and most popular collector of the century) by a dealer. Mr. Bond and others considered it to be merely a melanism or dark variety of the redwing, and Mr. Edward Blyth (whose technical and practical Eastern experience was very great) was the first to identify it as being a Siberian thrush. He mentioned it incidentally, in a note on the various rare thrushes which had occurred in this country, in The Field, September 24, 1870, p. 277, and since that date it has been generally accepted as a more or less genuine example, Yarrell (B.B,, 4th-ed., vol. I, p. 279 note), in particular stating that there seems to be no reason why the account should be disbelieved. [This was of course written by Newton. Eds.]. Mr. Gould, who figures the specimen in his Birds of Great Britain, vol. 2, states that it was a female and was shot by a Mr. Drewitt at St. Catherine's Hill, near Guildford, in the beginning of February, 1855, during the Crimean War. There is some discrepancy between the two accounts, but I think Mr. Gould's is probably correct, and, with the exception of the date, is not incompatible with the remainder of the other story. This identical specimen is now in the National Collection at the South Kensington Natural History Museum.
VOL. XLVIII] SIBEBIAN THRUSH ON THE MAY 25 Although the occurrence is not wholly free from doubt, it has been so generally accepted that I have no other option than to include it in the present volume. It may also be mentioned in support of its claims that it has occurred without question so near this country as Germany, Belgium, and France, so that its accidental appearance in England and in Surrey is not entirely improbable". The only additional information available that we have found is the statement by J. H. Gurney (Trans. Norfolk Nat. Soc, Vol. IV, p. 629) that Bond obtained the bird from "Mr. Smither of Farnham in Surrey, near which place it is believed to have been killed by a Mr. Drewett in February 1885 [sic, presumably a misprint for 1855]. Smither was a retired gamekeeper, and Gould gives him a high character in his article on the Dartford Warbler". [He was not therefore a dealer in the ordinary sense.] The main reason for doubting the validity of this record, where there is no question of the identification being wrong and where there is little likelihood of fraud since the bird was first regarded as a Redwing, appears to be the slight discrepancy over the dates. However, it seems obvious that the 1855 one is correct. Gould would not gratuitously mention the Crimean War if the event had actually occurred later and Gurney (allowing for an obvious misprint) supports him. It seems probable that the 1860-61 winter was the date when Bond acquired the bird from Smither, not that in which it was shot. EDS.]
PLATE 7 J). Q. Andrew SIBERIAN THRUSH (Turdus sibiricus) ON THE ISLE OF MAY, 1ST-4T11 OCTOBER I 954 The upper photograph clearly illustrates the slate-black plumage, the white stripe over the eye and the broad off-white tips to the inner webs of the outer tail-leathers (one has been turned out of position to show this); an indication of the white tips on all but the central tail-feathers can also be seen. This bird had an elongated upper mandible and this is just visible. In the lower photograph, the remarkable pattern on the underwing, rather like that of White's Thrush (Turdus dauma), is shown, (see page 21).