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Home , Bluethroat, Chat (bird), Indian blue robin, Luscinia, Siberian blue robin, Tarsiger

British VOLUME 70 NUMBER 9 SEPTEMBER 1977

Siberian Blue Robin: new to F. R. G. Rountree Autumn 1975 was remarkable for rare birds in western Europe, but the appearance of this east Palearctic in the Channel Islands was one of the most unexpected events

t 12.50 GMT on 27th October 1975, Philip J. Guille approached a A mist-net set under the canopy of sycamores Acer pseudoplatanus along• side scrub consisting of blackthorns Prunus spinosa at the head of the Banquette valley in Sark, Channel Islands. Hanging in the net was a small and, as he extracted it, PJG realised that the species was unknown to him. Although recalling a small Turdus or rather large, short-tailed Robin Erithacus rubecula in form, its basic plumage pattern of dark olive-brown upperparts and mainly white underparts recalled no small turdid regular in the west Palearctic. Having safely bagged the , PJG summoned assistance and shortly afterwards Alan Marsden, Mrs A. Marsden, my wife and I arrived to witness the customary handling of such a bird and its release. Initially, none of us recognised its identity, but eventually we all agreed that our description and the photographs taken by AM were of a cyane, in what was probably first-autumn female plumage. The record was accepted by the Sark Rare Bird Panel and, later, by the British Birds Rarities Committee, to which body we submitted it in view of the international importance of the occurrence. The rest of this paper gives the details of what was perhaps the most astonishing rarity of a great year for extralimital vagrants through• out western Europe.

The bird in the hand The bird was obviously a small thrush or and, during its extraction from the net, it gave the long, harsh calls typical of such . Its

{Brit. Birds 70: 361-365, September 19773 36l 362 Siberian Blue Robin form most recalled a Robin, but was made distinctive by a rather short tail and noticeably longer and more robust legs. The following description and measurements were taken: Upper mandible dark horn, lower paler; and of olive on the flanks and the under- mouth pinkish with blue cast. Iris dark wing. Plumage fresh and unabraded, except brown. Upperparts including tail uni• for slightly worn tips to the pointed tail formly dark olive-brown; sides of face and feathers. Legs and feet pink, darker in neck similarly coloured, but with slightly front. darker lores, a distinctive whitish-buff Weight 15.75 g. Wing 71 mm (maximum eye-ring and fine buff streaks on the ear- chord), tail 48.5 mm (almost square, but coverts. Wings also dark olive-brown, with outer feathers 5.5 mm shorter). Bill but with a wing-bar formed by reddish- (to skull) 14 mm, tarsus 27 mm. Approxi• buff tips of the greater coverts and with mate length from bill tip to tail tip 123 the folded flight feathers (actually the mm. leading edges of both primaries and Wing formula: 4th longest (4 mm longer secondaries) buffish-olive and appearing than primary coverts), 5th —0.5 mm, much paler than the rest of the upper- 6th —6.5 mm, 7th —9.0 mm, 8th —11.5 parts. Underparts basically white and mm, 9th — 13.5 mm, 10th and secondaries vividly so below the breast, but with olive- —15.5 mm, 3rd —2.0 mm, 2nd —8.5 mm; buff tips on the throat and strong mottling primary emargination obvious on 3rd, 4th of buff tipped olive on the upper breast and 5th, slight on 6th. The bird remained silent during handling and we were hopeful of studying it in the field. Unfortunately, upon release it flew off immediately, calling 'tchak' as it did so. We noted its flight as low and undulating and then it was gone as mysteriously as it had come. The process of identification We could find no hint of what species we had observed in any field guide or other common book of reference, but a wider search of the Palearctic literature showed us that, in addition to the Red-flanked Bluetail cyanurus, which occasionally reaches the western seaboard of Europe, there were several other small related chats to be considered. The search for one that was, like Tarsiger, strongly migratory led us to the Siberian Blue Robin and, with the aid of Kobayashi (1956), King et al. (1975), Dementiev and Gladkov (1968) and other references, we were able to complete the identification. The bird's measurements fell within the limited ranges given by Dementiev and Gladkov, except for the bill, which was 2 mm shorter than any of the 12 quoted, and its plumage accorded with that given for the adult female, except that we did not note the rufous tinge of the tail and uppertail-coverts mentioned by Dresser (1902) and Salim Ali and Ripley (1973), or the brown 'scales' on the breast stressed by King el al. (1975)- These last discrepancies may indicate that the bird was immature and certainly the presence of a wing-bar, like that of a young Robin, suggests a bird in its first year. The combination of the eye-ring, the rather short tail and the long, robust and pale legs was central to the diagnosis and any confusion with the. Black-throated Robin L. obscurus was prevented by the absence of white bases to the outer tail feathers. Against the possibility that must now exist of further occurrences, additional description of the Siberian Blue Robin is essential. Only the Siberian Blue Robin 363 adult male earns its name, its upperparts being almost wholly slaty-blue (palest on the forehead and crown) and interrupted only by black lores, cheeks and throat sides (providing a noticeable black band through the face on to the neck) and olive-brown flight feathers. The male's under- parts contrast markedly with the upperparts, being basically white, but often tinged with bluish-slate or grey-brown on the flanks and across the chest. Like the Red-flanked Bluetail, young males and old females may have their uppertail-coverts and tail washed with blue (King et al. 1975) and such birds would be confusable with Tarsiger on a brief rear view, particularly since tbey also share a prominent eye-ring with that species.

90. Siberian Blue Robin Luscinia cyane, probably first-year female, Channel Islands, October 1975 (A. Marsderi)

The Red-flanked Bluetail, however, shows orange-red flanks at all ages and it is not so short-tailed or noticeably long-legged. D. I. M. Wallace tells me that the character of captive males reminded him of a rather plump, long-legged, short-tailed Phoenicums and certainly most texts stress the frequent movement of the tail in both 'quivering' and 'cocking' actions. The alarm call of the Siberian Blue Robin is normally written 'chuck-chuck-chuck', but our experience indicates that it can sound sharper than that. In its normal range, the Siberian Blue Robin is a secretive, apparently rather silent chat, which spends much time on the ground. Clearly, it is another small rarity that may elude the sharpest- eyed observer. Fig. 1 illustrates the general character of the species and plate 90 shows the Sark bird in the hand. 364 Siberian Blue Robin Associated occurrences The migration of the Siberian Blue Robin is oriented to the southeast and, before our record, the species had not been reported west of Bengal (Salim Ali and Ripley 1973); the capture of one in Sark was thus unprecedented. Fuller research into its distribution, however, tends to lessen the surprise, for the Siberian Blue Robin is closely syrnpatric in central Asia with the Pallas's Warbler Phylloscopus proregulus, whose west European records are fast mounting, and other regular extralimital vagrants, such as Radde's Warbler P. schwarzL The Sark bird appeared

Fig. 1. Siberian Blue Robia Luscinia cyane. Left, adult male, with dark blue upperparts and black mask (extending to neck) contrasting with snow-white underparts; right (foreground), immature, with dark brown upperparts and mottled or scaled chest on mainly white underparts; and right (background), adult female, patterned as immature, but lacking pale covert tips (and often with blue tones in upperparts of older birds). Note, at all ages, obvious length of pale legs and dusky flanks, and, on immature and female, prominent eye-ring (Z>. i", M. Wallace) in the middle of a ten-day flood of such birds {Brit. Birds 69; 324) and there can be no doubt that this complex arrival was influenced by the presence of a strong easterly airstream out of Russia, created by a large anticyclone centred over the Baltic Sea. A review of other past records suggests that the Siberian Blue Robin is no more unlikely to reach Europe than the Siberian Thrush Turdus sibiricus and the Thick-billed Warbler Acrocephalus aedon or those two other astonishing occurrences in October 1975, the Luscinia and the Yellow-browed Bunting Emberiza chrysophrys {Brit. Birds 69: 346 and 357). Certainly, in the general autumn context of unprecedented 'reversed migration', we see no reason to doubt that the robin was a wild bird and this was also the view of the Rarities Committee, which examined the possibility of an escape. Notes on the species The systematics of robins, nightingales and other related small chats remain confused, but Dementiev and Gladkov (1968), Flint et al. (1968) Siberian Blue Robin 365 and Vaurie (1959) all placed the Siberian Blue Robin in the Luscinia —with ten other species, among which are the more familiar Nightingale L. megarhynchos and L. svecica. The Siberian Blue Robin forms a species-pair with the L. brunnea (but the latter undertakes a shorter migration from the to Ceylon at most and is a very unlikely candidate for vagrancy) and, like all its congeners, it favours dense ground cover at all times of the year. The Siberian Blue Robin is apparently the most terrestrial of its kind, with the adaptations of a relatively strong bill, long legs and short tail to show for such a niche. In its breeding range, which stretches east of the Altai across southern Siberia to Korea, it is a fairly common, occasionally abundant species of mixed forest. The breeding cycle begins in May, with males singing 'sweetly and melodiously' from low cover or the ground. The nest is on the ground and is usually well hidden. Eggs are laid in late May and through June; they are plain greenish-blue and range in size from 19.0 x 13.7 to 18,2 X 15.0 mm (Dresser 1902). Details of incubation and fledging periods are apparently unknown. Adults moult in the breeding range from the last ten days of July to mid August. Details of the dispersal from the nesting areas are incomplete, but autumn arrivals are noted in Burma in October. The winter range of the Siberian Blue Robin stretches from Assam eastwards through southeast Asia to southern China; it includes Borneo, Sumatra and the Philippines.

Acknowledgements I express my gratitude to Dr A. S. Cheke, C. E. Davies, J. N. Dymond, R. R. Kersley, Dr J. T. R. Sharrock, D. L M. Wallace and the Rarities Committee for their invaluable assistance. Summary An account is given of the first known European occurrence of Siberian Blue Robin Luscinia cyane, mist-netted on Sark in the Channel Islands on 27th October 1975. References A1.1, S., and RIPLEY, S. D. 1973. Handbook of the Birds of and Pakistan, vol. 8. Bombay. DEMENTIEV, G. P., and GLADKOV, N. A. (eds) 1968. Birds of the Soviet Union. Israel Pro• gram for Scientific Translations. Jerusalem. DRESSER, H. E. 1902. A Manual of Palaearctic Birds. London. FLINT, V. E., BOHME, R. L., KOSTIN, Y. V., and KUZNETSOV, A. A. 1968. The Birds of the USSR. Moscow. (In Russian.) KING, B., WOODCOCK, M., and DICKINSON, E. C. 1975. A Field Guide to the Birds of South• east Asia. London. KOBAYASHI, K. 1956. Birds of Japan in Natural Colours. Osaka. VAURIE, C. 1959. The Birds of the Palearctic Fauna. Passeriformes. London. F. R. G. Rountree, La Perronerie, Sark, Channel Islands