Blue Rock Thrush in Strathclyde: New to Britain and Ireland R
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Blue Rock Thrush in Strathclyde: new to Britain and Ireland R. A. Hume, on behalf of the Rarities Committee On 14th June 1985, Mrs Elizabeth McConnell wrote to the British Trust for Ornithology from Girvan, Ayrshire. The first lines of her letter caused immediate excitement: 'Enclosed please find "bird": we think it is a Blue Rock Thrush.' The letter gave brief details, and John Marchant responded with considerable interest: it was, indeed, a Blue Rock Thrush Monticola solitarius and, as such, potentially the first record for Britain. The specimen had arrived safely, but had begun to decay. Initial details given were that it had arrived at Skerryvore Lighthouse, Strathclyde, on 4th June and had been found dead by A. McConnell on 8th, after which it had been kept in a deep-freeze. The weather was fine, occasionally sunny, during the bird's stay, and it hopped about on the rocks of the small island. Mr McConnell suggested that dehydration might have been the cause of death, as there is no fresh water available on the island. Further correspondence revealed that Skerryvore is a pillar lighthouse on a rocky base with space for a helicopter pad and some small rocky areas, which are all completely awash in rough weather. There is no terrestrial vegetation at all. There were five or six birds present at the time the Blue Rock Thrush appeared, but it remained separate from them; it was not heard to call. A dish of fresh water was ignored by all the birds, and the rock thrush spent its time picking insects from the rocks. It was nervous when approached, always flying off out of sight behind the rocks when it realised it was being watched. It appeared to seek a crack in the rocks at night. Other birds on the rock usually include a few wagtails Motacilla, although they seem not to survive: the McConnells had previously found dead Common Snipes Gallinago gallinago and Oystercatchers Haematopus ostralegus after at least 60 waders had flown around the light at night, and noted a small 130 [Brit. Birds 88: 130-132, March 1995) British Birds, vol. 88, no. 3, March 1995 131 variety of passerine migrants, too, on occasion, often attracted to the light and not infrequently being killed by collisions with it. John Marchant examined the bird and considered that the amount of wear and the lack of damage to feathers around the bill or to the bill, claws and toes gave no cause to suspect captive origin. The specimen was transferred to a deep-freeze at the British Museum, Tring, but was too decayed to allow the preparation of a skin. R. A. Hume, 15 Cedar Gardens, Sandy, Bedfordshire SG19 1EY EDITORIAL COMMENT Dr David T. Parkin, Chairman of the British Ornithologists' Union Records Committee, has commented as follows: 'A BOURC file on Blue Rock Thrush has been in existence since 1966, but previous circulations have never resulted in the species gaining admission to Category A of the British & Irish List. A reappraisal of existing records took place during 1991-92, involving birds reported from North Ronaldsay, Orkney (29th August to 6fh September 1966); Rye, East Sussex (10th August 1977); Skerryvore Lighthouse, Strathclyde (4th-8th June 1985); and Moel-y-gest, Gwynedd (4th June 1987). There was no problem with the identity of any of these birds [all accepted by both the British Birds Rarities Committee and the BOURC]; the debate has always centred upon the likelihood of natural vagrancy versus escape from captivity. 'The intra-specific taxonomy of western populations of the Blue Rock Thrush is in need of revision. At present, three races are recognised, although there is clinal variation between them, and considerable overlap in the range of variation of both size and colour. The westernmost form is M. s. solitarius, which breeds in Mediterranean Europe, North Africa and across Asia Minor and the Middle East towards the Caucasus Mountains. It is largely resident or semi-migratory. M. s. longirostris is paler and greyer in colour and smaller in size. It breeds across Iraq and Iran into Afghanistan and is migratory, wintering from Egypt and Sudan across Arabia to Northern India. M. s. pandoo is both smaller and darker than the nominate race (Vaurie 1959; Cramp 1988). Dr Alan Knox examined the specimens in the Natural History Museum, Tring, for the BOURC, and concluded that there is sufficient variability within populations for it to be unwise to assign many individuals to a particular race on plumage alone, particularly in the field. 'According to the records of Tim Inskipp (Secretary of the BOURC), and earlier information from the late Derrick England, Blue Rock Thrushes were imported regularly into Britain from India until the late 1970s. These birds were probably of the race pandoo, and there seems to be little evidence that either of the other races has figured significandy in trade or importation. 'The caution against assigning racial identity on the basis of plumage colour is borne out by the North Ronaldsay bird. This was described as "decidedly lighter than the illustration" in the Peterson, Mountfort & Hollom Field Guide. Since pandoo moults in August/September, and thereafter darkens progressively with wear (Cramp 1988), the bird might, however, have been a recentiy moulted individual of that race. In the 1960s, Blue Rock Thrushes were still being imported from India, and the presence of damaged tail feathers on this bird has consistendy led to its placement in Category D rather than on 132 Blue Rock Thrush: new to Britain and Ireland the British List. The recent reappraisal did nothing to disturb this conclusion. The Rye bird also occurred at a time when there were still importations, and this led the Committee to conclude that the escape possibility was too high and so that record was also accepted into Category D. 'The Skerryvore bird died, and its remains were available for examination. Although not suitable for making into a study skin, the bird has been preserved by evisceration and freeze-drying, and is retained in the Natural History Museum at Tring. On plumage and gonadal characteristics, it has been identified as a first-summer male. Dr Alan Knox examined the specimen on behalf of the BOURC, and compared its measurements with skins from the collections there. The wing measured 121mm, which is shorter than that of any nominate solitarius males in BWP (Cramp 1988), and only one at the NHM was smaller than this specimen. The wing length is closer to the average for longirostris males, and is towards the upper limit for partdoo. The bill is slender; this character is also variable, but Knox could find no specimens from the west or central Mediterranean with a bill as slender as the Skerryvore bird. It fits better with longirostris and pandoo, but the depth of the bill is greater than that of many pandoo males. The bird was carrying several ectoparasites. These were kindly identified by Keith Hyett from the Natural History Museum. There was a larval sheep tick Ixodes ricinus, a species found on many wild and domestic animals. There were also several females of a mite tentatively identified as Bakericheyla chanayi (Cheyletiellidae), which is a new genus for Britain, although this is not unusual with such a difficult and little- studied group. 'Assignment of the Skerryvore individual to any particular race is probably unwise, but the specimen appeared closest to birds from the Middle East, and it was unlikely to have come from Western Europe. There was no evidence that soft-billed birds had been imported from the former region at that time, and the record was accepted into Category A of the British & Irish List (Ibis 135: 220-222). 'The Moel-y-gest record was also considered. As the acceptance of the Skerryvore bird meant that the species had already been admitted to the British List, this was not strictly necessary. The coincidence of dates with the Skerryvore bird (two years later to the day), however, and the lack of any evidence of damage to the plumage, led the BOURC to accept this bird also as a Category A record. It is worth noting that Tim Inskipp recorded an advertisement in Cage & Aviary Birds for this species "arriving soon" three weeks before the Gwynedd sighting and from a locality only 65 miles (100 km) to the northeast. 'It should also be noted that Blue Rock Thrushes have started to appear in captivity again in the last few years (Knox 1994) and featured in a recent centre-spread of Cage & Aviary Birds. Future records should be scrutinised with this in mind.' References CRAMP, S. (ed.) 1988. The Birds of the Western Palearctic. vol. 5. Oxford. KNOX, A. G. 1994. Vagrants on the cheap. Birdwatch Qune 1994): 40-44. VAURIH, C. 1959. The Birds of the Palearctic Fauna. Passeriformes. London. .