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SOME NOTES ON THE SPECTACLED WARBLER IN THE MALTESE ISLANDS BY JOHN GIBB.

OPPORTUNITY FOR OBSERVATION. FROM September 1941 until July 1945,1 was stationed in Malta and was able to devote much of my spare time to studying the bird-life of the islands. Malta, together with the sister isles of Gozo, Comino and Fihia, is primarily of interest to the ornithologist as a migrant station, for its breeding species are few. Among these few the Spectacled Warbler (Sylvia c. conspicillata) is prominent. Throughout my stay in the islands I was most concerned with keeping note of the shifting bird population, but it was inevitable that I should at the same time gain a closer acquaintance with the Spectacled Warbler than with any other single species. In the early spring of 1945, before the main influx of passage migrants was due, a slightly more intensive study and census of the species was made in order to fill some of the gaps in my previous notes. I was fortu­ nate in having the valued company and co-operation of Mr. D. A. Slight, of the Malta Command Signals, during the latter period.

STATUS, DISTRIBUTION AND HABITAT. The Spectacled Warbler is a sedentary resident on Malta, Gozo and Comino Is. I was unable to visit the rocky islet of Filfla, lying three miles to the south of Malta, which can scarcely boast sufficient cover even for this species; Wright (1863) did not find it there. Schembri (1843) first recorded the Spectacled Warbler in Malta as arriving in March and leaving again in September; a summer visitor. Some 20 years later, however, Wright (1864) described the species as being the only warbler that was a constant resident, and Despott (1916) agreed with this. (Despott inexplicably omits the Spectacled Warbler from his list in the Ibis, 1917). Mackay (1899) has evidently confused the present species with the Whitethroat (Sylvia c. communis) when he says of the latter that he "frequently found their nests"; in fact his notes are so full of inaccuracies that none can be taken seriously. I found no evidence of migration whatsoever, and numbers appeared constant throughout the year. This is perhaps the more curious as the Spectacled Warbler is migratory in Spain (Jourdain, 1937), France (Mayaud, 1936), Southern Italy and Sicily (Arrigoni degli Oddi, 1929) and even, to some extent, in Tunisia (Whitaker, 1905) ; there is also evidence of migration in Algeria (Ticehurst and Whistler, 1938). No matter where one may go about the Maltese islands one is bound to meet the Spectacled Warbler. It is as well at home along the rugged cliffs of the south-west coastline as in a thistle-patch in VOL. XL.] SPECTACLED WARBLER. 299 the corner of a flat field in the centre of the island. I found it on the rocky wastes at 800 ft. and on the ancient bastions of Valletta city itself. In fact the rougher and less cultivated the ground, the better it fares: for the bird shuns the few places on Malta where trees abound, notably in the Boschetto and the St. Anton Gardens —but this is not typical Maltese country. Yet the species is far from catholic in its tastes. It demands a very specialized breeding ground, which Malta can provide abund­ antly for it. It requires an open uncultivated patch with just enough low cover for the nest, no more and no less, Whether this patch be surrounded by cultivated land, barren acres of rock or by city buildings, as in Valletta, matters not at all. It is interesting to compare this Malta habitat with that elsewhere in the range of the Spectacled Warbler. It is common in Egypt on the scrubby desert fringing the Delta (Meinertzhagen, 1922). In the Camargue (Alexander et at., 1933, Glegg, 1931 and Yeates, 1943) it is almost exclusively a bird of the Salicomia scrub; in Sicily (Whitaker, 1905) it is confined to the higher mountain districts. In Tunisia (Whitaker, 1905) it is apparently common on the semi- desert plains and on the inland salt-marshes, whilst in some parts of the regency it is a common garden bird. South of the Atlas mount­ ains it frequents the low patches of Thymelcea hirsuta scrub where this gives way to the Saharan sands (Heim de Balsac, 1924, 1926, 1936) and breeds in Zizyphus scrub in Algeria and Morocco (Jourdain, unpub. and Lynes, 1925). It penetrates into the valleys and on to the open plateaux between Ghardaia and Zirara, some 350-400 miles due south of Algiers. In the Cape Verde Is. (Bannerman, 1939) S. c. orbitalis is found from sea-level to the mountain tops; here it favours acacia and other thickets and nests as high as 7 ft. from the ground. In the Canary Is. (Bannerman, 1922) the vertical range of its habitat extends from the semi-desert belt of the Maritime Zone up to 6,000 ft.; though showing a preference for the Euphorbia shrubs of the former.

FIELD CHARACTERISTICS AND GENERAL HABITS, Out of the migration season there can be no mistaking the Spectacled Warbler in Malta. No other resident species, summer or winter visitor can be confused with it, and the much greyer Sardinian Warbler (Sylvia m. melanocepkala) is the only other resident warbler. In the migration season confusion is perhaps most likely with the Whitethroat, but the Spectacled is redder on the wing coverts and this alone is always adequate for identification purposes. The white eye-rim from which the bird gets its name is difficult to detect under field conditions. The sexes are generally similar, but may be distinguished in a good light. In the breeding season especially the male is appreciably brighter and smarter than the female, but the differences are purely comparative. Juveniles resemble the female. 300 BRITISH BIRDS. [VOL. XL.

The birds are usually seen in pairs and remain together in one restricted locality all the year round. In Malta there is no suggest­ ion of the winter flocking recorded for S, c. orbitalis in the Cape Verde Is. by Bannerman (1939). Although capable of skulking behaviour at times and adept at disappearing into the absolute minimum of cover, the Spectacled Warbler is by no means secretive. They often pause in their activities to sing a brief phrase or scold an intruder, standing conspicuously erect with upcocked tail. Flight is low and direct except in the early breeding-season, when longer and higher excursions are taken. The birds feed in short vegetation, along the rough stone walls and on the ground ; I have seen insects taken on the wing.

VOICE. Notes are an high-pitched "tseet," used continually at all times, especially in company; and a scolding churr. This varies from a full-throated angry churr, rasping and metallic, down to a soft subdued mutter in mild annoyance, often used when preoccupied with more important business. The song is a sweet exhilarating warble of short duration, quickly repeated; not stereotyped. It resembles that of the Sardinian Warbler, but is less raucous. It is sweetest when sung with slow deliberation and quickly deteriorates in excitement as more squeaky notes are introduced. It is delivered from a prominent minor feature or occasionally early in the breeding-season from tree-tops up to about 20 ft. There is also the hovering or planing flight-song in spring, which is more hurried and less musical. Regular song is from the end of January, though a spell of warm weather may produce good song some weeks earlier. It continues unabated until the first eggs are hatched, thereafter diminishing gradually; by June it is almost silent. Autumn song begins in September and is a half-hearted affair. The sub-song is a soft faint echo of the normal song, uttered with closed bill.

DISPLAY AND POSTURING. Song flight. The bird rises from the ground or higher perch quickly and silently to about 30 ft., and then slowly descends singing with rapidly beating wings and fanned tail. Sometimes it rises no more than 6-10 ft., planing to the ground at a gentle incline as it sings. In anger or excitement the male alternates the scolding churr with outbursts of furious song ; the feathers of the crown are raised to an appreciable crest, wings drooped and tail cocked at an acute angle Courtship. The following procedure was noted once in March, 1945, The female was first seen sitting hunched and dishevelled in a low fig tree, whilst the male excitedly hopped from twig to twig within 18 ins., always keeping to the rear and slightly above the female. This continued for two or three minutes ; the male dancing VOL. XL.] SPECTACLED WARBLER. 301

about behind and above the female as if manoeuvring for an attack, but the female paying little apparent regard. The male eventually attempted to mount the female, but without success, for the latter immediately flew off a short distance to a stranded wire fence. The male followed closely and alighted on the strand above the female, then sang softly for a few moments. The female again flew off followed by the male and out of my sight. "Injury-feigning." (a) By female, when flushed from the nest at advanced stages of incubation and with young. An agitated flapping progress with broadly fanned tail for 2-5 yards over the ground. (b) By male, coaxing a snake away from young recently fledged. The bird lamely hopped and fluttered a couple of feet in front of the snake ; silent. When I interrupted the snake made off and the warbler altered its tactics to curse me roundly, churring and singing. (c) By male, luring a cat from the young, which were in the process of leaving the nest. The bird fluttered slowly over the ground, attracting the attention of the cat with a slight churring; then, when the latter gave chase, it half-flew and half-fluttered away until the cat was only two or three feet behind in headlong pursuit. It only left the ground at the very last moment, flying uncertainly a couple of yards ahead. The ruse was abandoned after the cat had been lured some 40 yards from the young.

BREEDING. Nest site. The vast majority of nests were within a foot of the ground ; some on it, and a very few as high as 2ft. 6ins. They are built in any low thick vegetation, matted grass, thistles and small dense shrubs. Nest construction The nest is similar to that of the Whitethroat and considerably less robust than that of the Sardinian Warbler. It is surprising to read that nests south of the Atlas Mountains are apparently more substantial. Heim de Balsac (1924) particularly remarks on their solidity, saying that they differ in this respect from the other breeding warblers of that area, Sylvia h. hortensis, S. a. atricapilla and S. m. melanocephala; Salvin (1859), on the other hand, described a nest from the same district as "loose but neat." The outer framework of dried bents, rootlets and old leaves (especially skeleton thistle leaves of the previous years' growth) is followed by a layer of soft down; a final loose lining of fine roots and a little hair is added. Both sexes build, the female taking the greater part in the later stages of the first nest at any rate. In April, 1945, I watched one male building a second nest while the female fed the young, which had flown from the first five days before : I cannot say if this was later used. The male sometimes builds "cock's nests." Construction of the first nest of the season is a casual affair and, if disturbed, the birds may stop work and disappear completely for 302 BRITISH BIRDS. [VOL. XL. an hour or so, allowing the nest to be inspected without a note in protest. Its building takes up to a fortnight, and two or three days may elapse between the completion of the nest and the laying of the first egg. I have no data for subsequent nests. Eggs. Eggs are laid one per day. The ground is dull white with greenish-brown, occasionally reddish-brown, fine spots zoned at both ends. Some are lightly spotted, others densely covered. In Malta the normal clutch-size is five; of nineteen clutches found sixteen were of five, two of four and one (a very late clutch com­ pleted on June ist) of three eggs. Five seems to be the usual clutch from Spain also; the seven clutches recorded by the late F. C. R. Jourdain (unpublished) are all of five. But in the Atlas Mountains " eggs in one nest seldom exceed four" (Salvin, 1859). Of nine clutches of S. c. orbitalis from Tenerife two were of five, five of four and two of three eggs (Koenig, 1890), and Boyd Alexander found four more commonly than five there; a clutch of six is also reported from the Canaries (Bannerman, 1939). Thus there is some indication of the latitude trend for clutch-size "to increase from the tropics outwards towards the poles" (Lack, 1947). Breeding-season. From March to June. In 1942 the first eggs were laid in five nests watched on March 3rd, 4th, 5th (2) and nth. In 1945 the dates for nine nests were March 6th, 7th, 9th, nth, 14th, 19th, 20th, 22nd and 23rd. The species is normally double-brooded. The last date recorded for the laying of a first egg in a clutch was May 30th (1944). These late nests are probably "repeats" although genuine third broods may well occur. In south Tunisia (Whitaker, 1905) breeding begins from mid- to end of March, and considerably later in the north. Bannerman (1922) found eggs of S. c. orbitalis in the Canary Is. from March 7th to May 5th. Incubation. Is by both sexes. Period 13 days ± 6 hours for first broods in March (two cases), and 12 days ± 6 hours for a second or possibly third brood in June. Period reckoned from laying to hatching of the last egg. I believe incubation normally begins with the laying of the last egg, but have twice flushed a female from the warm eggs of an incomplete clutch : once off three eggs and once off four eggs of clutches later completed to five. Writing of S. c. orbitalis, Reid (1887) oddly notes, ". . . .the birds sitting very close, even before incubation had commenced." Fledging. Young are fed by both parent birds; food is brought in the bill. Period 12 days ± 12 hours (two cases), reckoned from hatching of last egg to last young leaving the nest. In one instance recorded young of the last brood of the season were being fed three weeks after leaving the nest. Nest sanitation. Excreta are carried 15-20 yards from the nest, which is kept clean throughout the fledging period. Breeding ecology. In late February the winter visitors are VOL. XL.] SPECTACLED WARBLER. 303 beginning to leave and the bird population of the islands is steadily declining owing to their departure. But this is only a transitional period, for the sudden impact of the spring passage migration hits Malta in the last week of March*. In the first fortnight of April the bird density is at its peak, and this coincides with the most luxuriant stage in the growth of the indigenous herbaceous plants and shrubs as well as with the hatching of the first broods of the Spectacled Warbler. In the latter half of April the sun scorches the landscape to a browner shade ; the formerly crimson fields of flowering sulla (Hedysarum coronarium) are now cut and stooked, grasses withered and wheat ready for harvesting. The ecological conditions under which the Spectacled Warbler must rear its second brood thus differ enormously from those of its first. The brief super-abundance of early spring and its competition with a variety of insectivorous passage migrants is contrasted with a semi-desert of parched soil and shimmering rock. The trans­ formation is completed in a couple of weeks just when most pairs of Spectacled Warblers are in the initial stages of their second broods. The migrants have now dwindled away and the only other breeding species with an overlapping habitat are the resident Corn-Bunting (Emberiza calandra), the Short-toed Lark (Calandrella b. brachy- dactyla), a summer visitor arriving at the end of March, and the Sardinian Warbler, which keeps more strictly to the shade of the carob, fig and citrus-fruit trees.

POPULATION AND TERRITORY. These two aspects in the life of the Spectacled Warbler were studied concurrently from mid-February to mid-April, 1945, in the same restricted area. Description of area. Work was begun in mid-February on an area of approximately 100 acres. This comprised two short wieds joined at their lowest point and containing a broad spur of cultivated land in the angle between them. The highest point above Mean Sea Level was 300 ft. and the lowest 100 ft. There were two main factors governing the choice of this area: it had to be easily accessible and as nearly typical of Maltese country-side as possible. The cultivated spur was divided by stone walling into narrow terraced fields with, here and there, rock outcrops interspersed with coarse grasses, thistle, small shrubs, prickly-pear and stunted carob and fig trees. The crops were wheat, sulla, broad beans, field pea, potato, tomato and other mixed vegetables. In the wied bottoms there was a little rough pasture, but it was mostly rocky uncultivated ground. Census. This area contained 14 pairs of Spectacled Warblers, of which nine were centered directly on the wieds, and, by way of comparison, 12 pairs of Sardinians. The density for the area as a whole was therefore one pair of breeding birds to approximately *For arrival dates see antea, pp. 71-78. 304 BRITISH BIRDS. [VOL. XL. seven acres. The census was taken over a period of six weeks and includes breeding birds only. Owing to the open nature of the country it was found a comparatively simple matter to locate and keep track of these sedentary birds. Territory. This was loosely denned except in the steep and sheltered wied running north and south, where pairs were closest; there alone was it possible to trace the limits for each pair with any precision. Territory disputes were still of daily occurrence in mid-February, but the status quo had been restored with the start of actual breeding in early March. I arrived on the scene probably a month too late to see the initial boundaries being decided. The male advertised its territorial claims from vantage points around the territory, and trespassers, both neighbouring pairs and man, were greeted alike with aggressive song. If song proved an inadequate threat to other Spectacled Warblers, which was seldom, they were driven off without further ceremony. Two pairs, whose nests were but 15 yards apart, lived on the friendliest of relations and were seen to feed in company ; yet there was continual friction between two other pairs whose nests were separated by a full 75 yards. Other species were tolerated within the territory, and in fact those of the Spectacled and Sardinian often overlapped. I once watched a Spectacled Warbler harry an intruding cock Sardinian from the immediate vicinity of its nest.

REFERENCES. ALEXANDER, W. B., HARRISSON, T. H., PEASE, H. J. R. and TUCKER, B. W. (1933). Some Spring Observations on the Birds of the Camargue. Ibis, 1933. P- 527- ARRIGONI DEGLI ODDI (1929). Omitologia Italiana, p. 251. BALSAC, HEIM DE (1924). Voyage d'etudes ornithologiques dans la region Nord du Sahara. Revue Francaise d'Ornithologie, 1923-24, pp. 73-4. BALSAC, HEIM DE (1926). Contributions a 1'Ornithologie du Sahara central et du Sud-Algerien. MSmoires de la SocUtt d'Histoire Naturelle de I'Afrique du Nord, 1926, pp. 57-8. BALSAC, HEIM DE (1936). Biogeographie des Mammiferes et des Oiseaux de I'Afrique du Nord. Bulletin Biologique de France et de Belgique, Supple­ ment, xxi, p. 256. BANNERMAN, D. A. (1922). The Canary Islands, p. 296. BANNERMAN, D. A. (1939). The Birds of Tropical West Africa, Vol. v., pp. 25-27. DESPOTT, G. (1916). The Breeding Birds of Malta. Zoologist, 1916, p. 164. DESPOTT, G. (1917). Notes on the Ornithology of Malta. Ibis, 1917, pp. 281-349. GLEGG, W. E. (1931). The Birds of "L'lle de la Camargue et la Petite Camargue." Ibis, 1931, p. 229. JOURDAIN, F. C. R. (1937). The Birds of Southern Spain. Ibis, 1937, pp. 110-152. JOURDAIN, F. C. R. (unpubl.). Diaries and notes in possession of the Edward Grey Institute of Field Ornithology, Oxford. KOENIG, A. (1890). Ornithologische Forschungsergebnisse einer Reiser nach Madeira und den canarischen Inseln. Journ.f. Ornith, 1890, pp. 257-488. LACK, DAVID (1947). The Significance of Clutch-size. Ibis, 1947, pp. 302-352. VOL. XL.] SPECTACLED WARBLER. 305

LYNES, H. (1925). Ornithology of the Sous Territory of Southern Morocco. M&moires de la SociiU des Sciences Naturettes du Maroc, 1925, pp. 1-82. MACKAY, SERGEANT H. (1899). Ornithological Notes from Malta. Zoolo­ gist, 1899, p. 258. MAYAUD, N. (1936). Inventaire des Oiseaux de France, p. 128. MEINERTZHAGEN, R. (1922). Notes on some Birds from the Near East and from Tropical East Africa. Ibis, 1922, pp. 621-671. REID, S. G. (1887). Notes on the Birds of Tenerife. Ibis, 1887, pp. 424-435. SALVIN, O. (1859). Five Months' Birds'-nesting in the Eastern Atlas. Ibis, 1859, pp. 302-352. SCHEMBRI, A. (1843). Catalogo Ornitologico del gruppo di Malta. TICEHURST, C. B. AND WHISTLER, H. (1938). Autumn Impressions in Algeria. Ibis, 1938, pp. 717-748. WHITAKER, J. I. S. (1905). Birds of Tunisia, Vol. i, pp. 82-3. WRIGHT, C. A. (1863). A Visit to the Islet of Filfla, on the South Coast of Malta. Ibis, 1863, pp. 435-440. WRIGHT, C. A. (1864). List of Birds observed in the islands of Malta and Gozo. Ibis, 1864, pp. 163-5. YEATES, G. K. (1943). Some Field Notes on the Spectacled Warbler. Ibis, 1943, p. 68.