Marmora's Warbler: new to Britain and Ireland J. Lunn n the late evening of 15th May 1982, G. Lee telephoned me to say that, Iduring that day, at Mickleden Clough, Langsett, South Yorkshire, he had watched a small warbler which he could identify only as a Marmora's Warbler Sylvia sarda. At 07.00 GMT on the following morning, I located the continued.... [Brit. Birds 78: 475-481, October 1985] 475 476 Marmora's Warbler: new to Britain and Ireland bird and watched it for about 35 minutes before losing sight of it; shortly afterwards, it was found about 400m down the valley by other observers, including J. E. Dale. Its identity was confirmed as Marmora's Warbler. Throughout the next few months, until 22nd July, the warbler was watched by many hundreds of observers. It was photographed by A. V. Moon (Brit. Birds 75: plates 145 & 146), John T. Belsey, S. G. D. Cook and John Hewitt (plates 218-220). The record was subsequently accepted as the first for Marmora's Warbler in Britain and Ireland. Description First impressions were of a small warbler, strikingly blue-grey in colour, closely resembling a Dartford Warbler S. undata in shape, and with a noticeably long tail. PLUMAGE Striking: at a distance appeared brown-washed grey or buffy-grey; feather uniform blue-grey, recalling adult Cuckoo tips appeared abraded. Cuculus canorus, this emphasised by dark vege• BARE PARTS Legs originally described as tation background. At closer range, head straw-yellow, later as yellow-orange (differ• appeared darker, especially around lores, ence perhaps due to lighting effects?). Bill and at close quarters various grey-blue hues appeared sharply defined pale at distance, of varying quality and intensity visible on accentuated by dark background and grev head and neck. Underparts slightly paler, plumage; at closer range, upper mandible especially towards belly. Wings grey; re- pale horn, base and lower mandible pale miges often appeared paler, especially in yellow. Eye blood-red. surrounded by blood- bright light (this effect perhaps caused by red orbital ring, conspicuous at close outer webs or feather shafts being paler, or quarters. Mouth pale straw-yellow, striking reflecting light). Tail variously described as when bird singing. Habitat Mickleden Clough is a steep-sided gritstone valley situated at 1,400 feet (426 m) in the southern Pennines. A small, fast-flowing stream meanders northwards through the valley bottom, where the vegetation is dominated by grasses (Nardus, Agrostis and Molinia) and wet flushes of moss Sphagnum, rushes Juncus and cottongrass Eriophorum. The valley sides are dominated by 218. Marmora's Warbler Sylvia sarda, South Yorkshire, May-July 1982 (John T. Belsey) Marmora's Warbler: new to Britain and Ireland 477 heather Calluna vulgaris, bilberry Vaccinium myrtillus, cowberry V. vitis-idaea and bracken Pteridium aquilinum. Small rocky outcrops and quarries are also a feature of the habitat, as too is an almost complete lack of tree cover apart from isolated rowans Sorbus aucuparia and hawthorns Crataegus monogyna on the slopes and a line of mature mixed deciduous trees for about 400m in the valley bottom. General habits and behaviour Throughout its stay, the warbler frequented the steep eastern side of the valley, and was only occasionally recorded in the valley bottom. It occupied almost exclusively an area of about 400m X 50m (its apparent territory) comprised mainly of heather about 0.5 m tall and bilberry interspersed with grass patches and bracken. It was generally very active within this whole area, continuously moving short distances through the vegetation and then flying 30-40 m. The warbler frequently perched and sang, usually on top of some heather, but was out of sight to the stationary observer for consider­ able periods of time. When perched it occasionally cocked its tail to about 45° in Dartford Warbler manner. The Marmora's Warbler frequently gave display. This was very much like that of a Whitethroat S. communis: a steady fluttering ascent to 4-7m above the heather at an angle of 60°-70° to the horizontal, with legs trailing, singing continuously, followed by a very steep undulating dive to alight usually farther down the slope. Display was noted over the whole length of the warbler's territory, and no particular song perches were used ex­ clusively. Collection and carrying of nest material (dry grasses and cobwebs) was seen on a number of occasions, especially during the early part of the bird's stay. The warbler attempted to catch flying insects just above the vegetation, and also moved through the vegetation as if foliage-gleaning. On one occasion, I observed it moving over bare ground under the heather in the manner of a Dunnock Prunella modularis, apparently foraging. No agonistic interactions were reported with any of the breeding Meadow Pipits Anthus pratensis, Skylarks Alauda arvensis and Whinchats Saxicola rubetra. Only one other Sylvia warbler was noted in the vicinity: a Garden Warbler S. borin on 16th May; again, no encounter was observed. Voice The Marmora's Warbler frequently sang throughout the day, at times almost continuously, and often this was the only indication of its presence. The individual song seemed to comprise a two-to-three-second phrase of a weak warbling quality, lacking both strong notes and rich tone; a diagnostic trill, recalling a weak or distant snatch of Wood Warbler Phylloscopus sibilatrix or Tree Pipit Anthus trivialis song, often punctuated and invariably terminated the song. The tonal range was narrow, and the total impression was of a weak quality, recalling Dunnock. A call note was heard infrequently. I described it as a sharp 'twik', typical of Sylvia, but having a more chat-like quality. 478 Marmora's Warbler: new to Britain and Ireland 219. Marmora's Warbler Sylvia sarda, South Yorkshire, May 1982 (S. G. D. Cook) Status and distribution of Marmora's Warbler The distribution of Marmora's Warbler is shown in fig. 1. Two races are generally accepted. The race balearica is confined to the Balearic Islands (Vaurie 1959), where it is largely resident (Berthold & Berthold 1973; Serra 1978). The nominate race sarda breeds in Corsica, Sardinia and possibly Sicily, and winters in North Africa (Vaurie 1959); it is also present in Spain on the Mediterranean coast (e.g. Rolfe 1965; Iribarren 1968; Wallace & Sage 1969; Navarro Medina 1972) and even inland (e.g. Jeffrey 1969; van Impe 1971), and has been recorded on southward passage in Gibraltar (Cortes et al. 1980). This same race has also been found on many of the smaller islands and islets scattered through the western Mediterranean, although its distribution there is, like that of the Dartford Warbler, poorly understood (e.g. Erard^a/. 1972): both species occur on some islands, only one of either species on others, while neither is present on yet other islands (Moltoni 1967, 1968a, 1968b, 1970). Marmora's Warbler has been recorded on passage, commonly in some years, on Malta, where it has also bred (Bannerman & Vella-Gaffiero 1976). In North Africa, Marmora's Warbler is a winter visitor to Algeria, Tunisia and Libya, and accidental in Egypt (Etchecopar & Hue 1967); in Tunisia, it may also be a rare and sporadic breeder (Thomsen & Jacobsen 1979). Numbers fluctuate, however, and the species can be rare in some years and common in others, for example in Libya (Bundy 1976). Marmora's Warbler has been recorded occasionally in northern Italy, in Liguria and Calabria (Toschi 1969; Spano & Podesta 1981). There is one Marmora's Warbler: new to Britain and Ireland 479 Fig. 1. Distribution of Marmora's Warbler Sylvia sarda: breeding stippled; winter hatched; isolated records large dots authenticated record from Roussillon, southwest France, on 28th April 1973 (Afire 1974); although other observers (e.g. Siebert 1970) have claimed Marmora's Warbler in this region, both Afire (1974) and Yeatman (1976) maintained only the one mainland French record. Origin The occurrence of a Marmora's Warbler some 2,100 km north of its previously known range immediately raises questions concerning its origin. The possibility that it had escaped from captivity is insignificant, since, although some Mediterranean Sylvia warblers are kept in captivity in Britain, the number of Marmora's is probably tiny, if indeed the species is kept at all (T. Inskipp in lift.). Furthermore, the likelihood of an aviculturist losing or deliberately releasing a male in near-immaculate breeding plumage (and presumably valuable) which was not even close-ringed is too remote to be plausible. Vagrancy by the subtly different Balearic race (Williamson 1976) can also effectively be discounted owing to its sedentary nature. 480 Marmora's Warbler: new to Britain and Ireland 220. Marmora's Warbler Sylvia sarda, South York• shire, May-July 1982 (John Hewitt) The most likely solution seems to be a spring overshoot of the nominate race, which would correspond closely to the records on the French and Italian Mediter• ranean coasts in mid or late April. Climatic conditions prevailing at and just before the time of the Yorkshire bird's arrival, with high pressure building on the Continent and a warm southerly airstream originat• ing well to the south, also support this view. As usual in May, various typical Mediterranean species, such as Little Egret Egretta garzetta, Subalpine Warbler S. cantillans and Lesser Grey Shrike Lanius minor, were all recorded in Britain on 15th or 16th May 1982 (Rogers et al. 1983). Perhaps even more significant was the occurrence in early June of another typical North African species, a White-crowned Black Wheatear Oenanthe leucopyga, in Norfolk; full details will be published shortly. Discussion A remarkable correlation in habitat occurs between that of the Yorkshire bird and the species' natural biotope on the Mediterranean islands.