Studies of less familiar birds 143. Subalpine Warbler By eoffrey Beven Photographs by M. D. England (Plates 13-16)

THE SKULKING HABITS of the Subalpine Warbler Sylvia cantillans make it difficult to observe. The male is distinctively coloured, how­ ever, with unmarked throat and breast of bright chestnut shading to pale pinkish-buff on belly and flanks; the chestnut throat is separated from blue-grey upper-parts by a characteristic white moustachial stripe which extends from just below the base of the bill to beneath the ear- coverts. This stripe may appear as if prolonged into the pale lower mandible (plates 13,14a, 16b). The dark tail is bordered by white outer feathers and rounded at the end (plate 16a). At close quarters an orange- red orbital ring is well-defined in both sexes and even nestlings may begin to show this (plate 13). Some males are not as brightly coloured

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123 BRITISH BIRDS as others, but the females and young are normally much duller with drab brown upper-parts and a buffish-white throat (plate 14b); older females sometimes develop a pink throat and a recognisable moustachial stripe. Subalpine Warblers and Dartford Warblers S. undata are often found breeding near each other, but the former are distinguished by their paler upper-parts, unspotted throat and shorter tail. The females and young also have to be distinguished from the corresponding plumages of Sardinian Warblers S. melanocephala and Spectacled Warblers S. conspicillata. In these plumages, however, Subalpine Warblers are much paler (especially on the crown) and more buff than Sardinian Warblers which have greater contrast between cheek and throat and appear dark and heavy-looking in the field; female and young Spectacled Warblers have a striking chestnut wing-patch, while Subalpine Warblers have only an inconspicuous pale brown one (Sharrock 1962, Swift 1959).

RANGE The Subalpine Warbler has a restricted breeding distribution confined to most countries and some islands of the Mediterranean Basin, though not in Egypt or Israel. The typical race breeds in Iberia, southern France, Italy, Corsica, Sardinia and perhaps Malta, but apparently not in the Balearics (Bannerman 1954). The two other subspecies generally accepted are albistriata in the Balkans, Crete, and perhaps Asia Minor, and inornata in north-west Africa. The distribution limits lie within the July isotherms of 73°F and 86°F (Voous i960), but possibly the main reason for the species' restricted range is its preference for certain types of xerophytic scrub and heath characteristic of Mediterranean lands. The species is generally regarded as a summer visitor to Europe, but summary statements vary from 'European populations migratory' (Vaurie 1959) to 'partial migrant' (Witherby et al. 1938-41). Migrant Subalpine Warblers winter among the acacia scrub on the western and southern edges of the Sahara east to about Lake Chad, but it is not clear what happens to any which do not migrate. No evidence of wintering individuals could be found in Malta by Gibb (1951), in northern Tunisia or north-eastern Algeria by Snow (1952) or in western Morocco by Smith (1965). Nevertheless, it seems likely that at least those which breed early in southern Iberia may have wintered there. On return migration in spring many Subalpine Warblers use a more easterly route and so, besides being plentiful in Tangier in March and along the east coast of Tunisia in early April, they also appear in large numbers in late March in Tripolitania, Cyrenaica and Egypt where they are rarely seen in autumn. They are said to arrive in southern Spain from the second week of March to the end of April. For further discussion of migration see Moreau (1961).

124 SUBALPINE WARBLER STUDIES In spite of its southern range the Subalpine Warbler is sometimes recorded much further north in Europe. In fact, there are now 25 records for Britain and Ireland, 19 of them since 1951. No less than twelve of these have been in Scotland, including seven on Fair Isle, while England has produced eight, Ireland four and Wales one. Two have been in April (both in 1964), ten in May, six in June, one in July, three in September, two in October and one in November, the extreme dates being 19th April and 3rd November. Williamson(1964) suggested that the spring records on the north and east coasts might involve mainly individuals of the eastern race albistriata which had overshot tbeir normal range in anticyclonic weather and he proposed that special attention should be paid to subspecific identification in the future. (The male of this race tends to have a broader moustache and to average rather darker on the throat and breast, the female tends to be whiter below, and the second primary in both sexes is usually slightly longer than the fifth, but these are only moderately well differentiated subspecies and individuals may be difficult to name.) On the other hand, records from Ireland and western Britain may chiefly involve the western cantillans, either as a result again of overshooting in spring or of post-juvenile dispersal in autumn. The species has also been recorded in the Netherlands at least twice and three times on islands off the north coast of Germany.

HABITAT The main habitat of the Subalpine Warbler is xerophytic and often thorny scrub characteristic of the sun-baked, stony and arid soil on the slopes of hills and mountains in the Mediterranean area. Such vegeta­ tion can be divided into two main types of 'maquis' and 'garrigue'. The maquis consists of the small trees and evergreen shrubs which remain after the destruction of oak woods and usually contains the short, evergreen, spiny-leaved holm oak Quercus ilex and the stunted, thorny kermes oak Q. com/era with such other trees as myrtles, Myrtus com­ munis, wild olives Oka europaea, junipers Juniperus and strawberry trees Arbutus unedo, often bound by thorny creepers into an impenetrable thicket. In places such habitats have degenerated even further as a result of drought or repeated forest fires into garrigue, a sparse and scrubby growth that is a prelude to bare, stony wasteland. Garrigue is also favoured by this warbler whose habitat may then consist mostly of cistus Cistus, broom Cytisus and other small shrubs or a kind of low heath scrub with such fragrant plants as thyme Thymus, rosemary Rosmarinus and lavender "Lavandulaan d perhaps with the odd kermes oak and dwarf palm Chamaerops humilis. Nevertheless, the Subalpine Warbler also breeds not infrequently in less arid situations, such as thick hedgerows with oak, bramble Rubus

125 BRITISH BIRDS and bracken Pteridium aquilinum, and alongside streams among rush and oleander Nerium oleander, while near Portel in southern Portugal its partiality to small ravines in the neighbourhood of streams is very marked (H. W. Coverley unpublished, Voous i960, Witherby et al. 1938-41). It may also be found breeding in open woodland with luxuri­ ant undergrowth, and Snow (1952) recorded it in noith Tunisia and north-east Algeria in forests of cork ozkQuercus suber and also in pure forests of Atlas cedar Cedrus atlantica, inhabiting bushes between the large well-spaced trees. Voous (i960) has pointed out that the Sub- alpine Warbler inhabits higher and more hilly regions than the Spec­ tacled Warbler, and it nests as high as 7,000 feet in the High Atlas in Morocco (Bannerman and Priestley 1952). It inhabits garrigue more frequently and pure dense maquis less frequendy than the Dartford Warbler, but may occur in the maquis beside Dartford and Spectacled Warblers. The Sardinian Warbler prefers high maquis with taller shrubs, but there may be some competition with the Subalpine Warbler; when the sedentary Sardinian Warblers almost vanished from the south of France in the severe winter of 1947, most of their habitats were occupied in that spring by Subalpine Warblers (Voous i960). Coverley (1939) has remarked that the breeding habits of these two species are closely associated in Portugal and we certainly found them side by side there in maquis scrub; I noted the same association in a similar type of scrub near Aries, France, in May 1948, since recorded by Hoffmann (1958).

GENERAL HABITS Since it spends so much of its time actively searching dense low scrub, this little warbler is difficult to glimpse more than momentarily as it suddenly appears and then quickly vanishes in the depths of a bush. In its flight and movements it resembles a Whitethroat S. communis, and the crown feathers are often erected to form a slight crest (plate 16b). When excited it raises its tail much like a Dartford Warbler does and it sometimes keeps it continuously cocked while feeding in tree tops (Sharrock 1962). In summer and winter its food consists mainly of insects and their larvae collected in scrub and also in the foliage of olives, oaks and other trees. Witherby et al. (1938-41) could specify only beetles and cater­ pillars and also a few small grass seeds, but Armitage (1930) noted fragments of the wings of moths below the nest. Bannerman (1953) mentioned a fondness for Salvadora berries in winter quarters in West Africa, and Williamson (1952) recorded that a migrant on Fair Isle fed 'industriously' on gnats (Chironomidae). At nests in Portugal we saw the young being fed on caterpillars and the larvae of flies (Diptera). on crickets and spiders and at least five times on green stick-insects (Phasmidae) between \\ and 2 inches long, though on many visits the

126 SUBALPINE WARBLER STUDIES bundles of small insects brought by the adults defied identification. Noisy alarm notes are frequently uttered and have been variously transcribed as tac-tac, tec-tec, or chit-chit, or likened to a clicking sound; these notes may be run together to produce a quick chattering alarm. The song is Whitethroat-like and lively, but more sustained and musical, with some rather prolonged and sweet notes, sometimes including harsh squeaky and rattling ones as well, although often without these. The bird usually sings from the cover of scrub or lower branches of trees, but sometimes from an exposed spray or while performing a pretty dancing flight from one bush or tree to another. A sweet but subdued warbling subsong was often heard from males perched close to hides (Armitage 1930). Yeates (1946) described how in courtship display 'the cock makes conspicuous use of the attractive black and white pattern on the underside of his tail. This in posturing he keeps cocked up in the attitude of a blackbird alighting and it is fanned open to full stretch so that the white outer tail feathers are shown to full advantage. Thus, with shimmering wings, he moves about the female.' 'Injury-feigning' has been observed when nestlings are being handled, the female flutter­ ing among the plant stems and over the ground with wings and tail outspread and head held out in front, gliding along as if driven by clockwork (Armitage 1930).

BREEDING The nests are usually in low bushes, especially in gorse Ulex, myrtle or brambles, and often in cistus or even among rush and oleander, between one and three feet from the ground; they may occasionally be in the lower branches of small scrub oaks or even stone pines Pinuspinea. We found three nests in Portugal in 1965. One was about 18 inches above the ground in the centre of a small patch of dwarf holm oak about two feet high (plates 13-15); a second was 22 inches above the ground and supported by branches of broom and bracken in a large patch of broom about four feet high (plate 16a); and the third was about twelve inches up in bramble, bracken and scrub oak by the side of a road. The first two were neat cup-shaped structures of coarse grasses, lined with much finer ones, and incorporating a certain amount of white vegetable down and a few small leaves, including prickly ones from the holm oak; the nest in plates 13-15 was three inches across and z\ inches deep, with the inside of the cup two inches wide and two inches deep. The third nest was much more bulky and coarsely constructed with thicker and longer grass stems, and also corn stalks, sticking out round the edge and with dry leaves and bracken incorporated. Armitage (1930) also described a more bulky nest in gorse and a more compact one in cistus, the latter lined with wool and goat hairs; Sharpe (1897) mentioned

127 BRITISH BIRDS the inclusion of thistle leaves in the main structure and a lining of long horse hairs. In Portugal and southern Spain the breeding season starts in early April. Full-grown young have been seen on the wing at 3,000 feet in the Sierra de Gredos on 6th June, while eggs have been found there as late as 8th June and in the Middle Atlas in Morocco as late as 16th June (Armitage 1930, Bannerman 1954, Snow 1952). Our third nest was incomplete and unlined on 22nd May, but contained three eggs by 31st May. These were whitish, heavily blotched with reddish-brown especially at the obtuse end. According to H. W. Coverley, this ery- thristic type is the rule rather than the exception in Portugal. Armitage described two types in Spain: (1) drab, pale buff or greenish with brown and grey spots; and (2) white or pink with reddish spots and small frecklings. Pure white eggs also occur. Coverley considered three or four to be the usual clutch (five in only one instance), but Armitage found that three to five eggs were common in the first clutch, whereas four to five were 'invariably' laid in the second. Armitage never saw a male close to a nest with eggs and it seems to be generally considered that incubation is chiefly by the female, although H. Lynes once flushed a male from eggs (Witherby et al. 1938-41). It is of interest, therefore, that over a period of at least six hours' observation from the hide at our second nest on 1st and 2nd June M. D. England noted that the male and female took alternating sessions of almost exactly 30 minutes each in incubating the three eggs (plate 16a). Similarly, during a two-hour watch on 3rd June I found that the male incubated for a total of 5 2 minutes in four sessions varying from seven to 19 minutes, and the female for 54 minutes in four sessions varying from three to 2 5 minutes. Each sat very closely and would not leave until approached within three feet; they both flew off quite quietly when flushed, but soon returned. At each of the two nests with four young which we watched from hides, one in the first week of May and the other in the last week, the young were fed by both sexes and it actually appeared to us that the male took the greater share. On the other hand, Armitage found that the male fed the nestlings only on rare occasions and he put this down to the close proximity of his hide. The food brought at both our nests sometimes seemed rather too large for the size of the young; this applied particularly to the green stick-insects which tended to remain protruding from a nestling's gape like a cucumber and then be gradually swallowed in a series of gulps. When it was very hot the female would stand on the nest, gasping in the heat, with wings partly outstretched to shield the young from the sun (Armitage 1930). With young in the nest, both male and female scolded persistently while skulking among the bushes.

128 SUBALPINE WARBLER STUDIES

ACKNOWLEDGEMENTS I am extremely grateful to Derrick England for helpful advice and for allowing his observations to be incorporated. We had much patient help in the field from other members of the party, especially Jack and Beryl Hulbert. John Armitage kindly sent us information and we were fortunate in having access to the unpublished records of the late H. W. Coverley. It is also a pleasure to thank Miss Maisie Collyer for translations from the German; and R. W. J. Uffen and the staff of the British Museum (Natural History) for help with the identification of insects and botanical specimens.

REFERENCES ARMITAGE, J. (1930): 'Field notes on the Subalpine Warbler'. Brit.Birds, 24: 176-178. BANNERMAN, D. A. (1953): The Birds of West and Equatorial Africa. Edinburgh and London, vol. 2: 1017-1019. (1954): TheBirdsof the British Isles. London, vol. 3:152-155. and PRIESTLEY, J. (1952): 'An ornithological journey in Morocco in 1951'. Ibis, 94: 406-433, 654-682. COVERLEY, H. W. (1939): 'Nesting notes from Portugal, 1937-8'. Ibis, 23: 149-152. GIBB, J. (1951): 'The birds of the Maltese Islands'. Ibis, 93: 109-127. HOFFMANN, L. (1958): 'An ecological sketch of the Camargue'. Brit. Birds, 51: 321- 350. MOREAU, R. E. (1961): 'Problems of Mediterranean-Saharan Migration'. Ibis, 103a: 373-4^7.580-623. SHARPE, R. B. (I 897): A Hand-book to the Birds of Great Britain. London, vol. 4: 299- 300. SHARROCK, J. T. R. (1962): 'The field identification of Sardinian, Subalpine and Spectacled Warblers in autumn'. Brit. Birds, 5 5:90-92. SMITH, K. D. (1965): 'On the birds of Morocco'. Ibis, 107: 493-526. SNOW, D. W. (1952): 'A contribution to the ornithology of north-west Africa.' Ito, 94: 473-498. SWIFT, J. J. (1959): 'The separation of Subalpine and Spectacled Warblers in juvenile and first-winter plumages'. Brit. Birds, 5 2:198-199. VAURIE, C. (1959): TheBirdsof thePalearcticFauna. London, vol. 1: 266-267. Voous, K. H. (i960): Atlas of European Birds. London, pp. 227-244. WILLIAMSON, K. (1952): 'Subalpine Warbler at Fair Isle'. Brit.Birds, 45: 260-261. (1964): Identification for Ringers. 3. The Genus Sylvia. B.T.O. Field Guide No. 9. Oxford. WITHERBY, H. F., et al. (1938-41): The Handbook of British Birds. London, vol. 2. YEATES, G. K. (1946): Birdhife in Two Deltas. London, p. 123.

129 PLATE 13. Male Subalpine Warbler Sylvia canlillans at nest, Portugal, May 1965. Note the white moustache which separates the chestnut-pink throat from the blue- grey upper-parts, and also the orange-red eye-ring and the cocked tail. This nest was about 18 inches up in a dwarf holm oak (pages 123-129) (photo: M. D. England) PLATE 14. Subalpine Warblers Sylvia cant Mans, male above and female below, Portugal, May 1965. These two photos show the pair in the same typical stance. Note the female's pale throat and consequent absence of moustache; older females which develop pink throats then show the stripe (page 124) (p/jo/os: M. D. England) PLATE 15. Female Subalpine Warbler Sylvia cantillans with male visible behind leaves on right; this is typical of the way one of a pair of passerines will wait as the other feeds the young. The female has a cricket; other food included fly larvae, caterpillars, spiders and stick-insects (page 126) {photo: M. D. England) PLATE 16. Male Subalpine Warblers Sylvia cantillans at two more nests, Portugal, May-June 1965. Above, incubating (page 128) on nest in broom and bracken; note white outer tail-feathers used in display (page 127). Below, at roadside nest in brambles, bracken and scrub oak; the eye-ring shows well {photos: M. D. England)