Studies of Less Familiar Birds Iy6 Barred Warbler D

Studies of less familiar birds iy6 Barred Warbler D. A. Christie Photographs by A. jV. H. Peach and J. B. and S. Bottomley Plates 12-15 The French 'Fauvette eperviere', German 'S^rforgrasmiicke' and Swedish '.HoAsangare' are all vernacular names for the Barred Warbler Sylvia nisoria. The italicised parts of these continental names all mean Sparrowhawk Accipiter nisus and allude to the superficial resemblance between the two, a notion reflected in several other European names for the species; even the specific name nisoria means 'sparrowhawk-like'. In reality the only similarities are barred underparts and a long tail, but these features certainly distinguish the Barred Warbler from other members of its genus. A large, bulky warbler, at about 15 cm roughly the size of a Red- backed Shrike Lanius collurio, it presents at first sight an essentially uniform grey appearance as it slips into cover. The adult male is grey-brown above with two narrow pale wing-bars, and whitish or pale grey below, the underparts being barred with dark crescent- shaped marks which extend to the flanks and undertail-coverts, where they are often more pronounced. The barring is less con spicuous in autumn and winter, while during the breeding season it varies considerably from one male to another, some individuals being very heavily marked and others showing just suggestions of bars on the flanks and undertail-coverts with the breast almost uniform pale grey. The long tail has white in the outer feathers, particularly at the tips, but this is often difficult to perceive in the field except when the bird alights or enters a bush, when the tail is fanned. In the female and juvenile the upperparts are browner and the barring less distinct, being absent or nearly so in the majority of juveniles, though again it is often present on the undertail-coverts. The strong legs are dark and the noticeably large bill a dark horn. Adults have staring yellow irides which can be striking at close quarters (see plates 12, 14 and 15). The long, sloping forehead and high, rounded crown also lend the bird a distinctive, powerful and rather aggressive appearance. Young Barred Warblers might be confused with a number of other Sylvia warblers, particularly immature Garden Warblers S. borin and Whitethroats S. communis, but the large size, stout bill 108 {Brit. Birds, 68: 108-114, March 1975] Barred Warbler studies 109 and long tail should be sufficient to preclude any real difficulties in separation provided adequate views are obtained. (See photo graph in Limosa, 38: 102, where the stouter bill of this species is obvious in comparison with that of a Garden Warbler.) Caution is also required in separating them from grey Hippolais warblers, particularly the large Olive-tree H. olivetorum which also has a long, stout bill. The Barred Warbler is an east European and west Asiatic species. It breeds from about io°E in Europe, between the Baltic states in the north and the Balkans in the south, eastwards between about 56°N and 36CN to north-west Mongolia, just reaching northern Afghanistan (Vaurie 1959). Birds from Turkestan eastwards are paler and greyer and have been assigned to a separate subspecies merzbacheri. In Europe the Barred Warbler has extended its range north-westwards, small populations having become established comparatively recently in south Finland and southern Scandinavia. Indications that it may still be spreading north-west are provided by the first breeding record in the province of Sodermanland in Sweden in 1963 and 1964 at 5g°8'N (Jenning 1965); in June 1972 breeding was confirmed for the first time in Norway, at Molen in Vestfold (Numme et al. 1973), where the species had been an annual summer visitor since 1969. The preferred habitat is thick shrubbery, usually thorny, on commons and meadowland. Damp meadows of willow Salix and ash Fraxinus are also frequented, as well as loose willow plantations interspersed with buckthorn Rhamnus, birch Betula and scattered firs. In parts of Bosnia and Herzegovina habitat consisting of oak Quercus, willow and hawthorn Crataegus is occupied, and in Montenegro shady deciduous forest (Niethammer 1937, Steinfatt 1938, O. Reiser in Melcher 1952). The Barred Warbler is found also in bushy allotments, parkland and overgrown clearings in woods, though it normally avoids extensive forest. In the eastern parts of the range it occurs in mountains up to 2,300 metres above sea level (Dementiev and Gladkov 1968). A notable feature is the species' preference for damp situations, and a great liking is shown for wet meadows and overgrown ditches, while it is also found, some times in some numbers, in open, bushy peat bogs. In Poland Gotzman (1965) found that low, thick bushes intertwined with tall grasses were a prerequisite for colonisation by the Barred Warbler, while a moderate weed layer and isolated tall bushes were a preferred addition to the habitat. Within all these habitats the Barred Warbler occurs irregularly and locally scattered, though pairs may occasionally nest only 100 metres or so apart. It is one of the most skulking of its genus and, especially during the breeding season, may easily be overlooked. no Barred Warbler studies Since Barred Warblers prefer to feed in thick cover, perhaps the best clue to their presence is the voice. The remarkably loud, harsh alarm call, once learned, is unmistakable. It is usually uttered from cover, though it is not rare for a bird, when taken by surprise, to emit diis metallic, grating sound from an open perch before darting for cover. The call is best transcribed as 'tcherrr' or 'terrrr', dimini shing in speed and often followed by several softer, subdued notes 'tjed, tjed'. A second common utterance used in excitement is a series of short, metallic notes, increasing in pitch and speed as the excite ment intensifies and often heard when an intruder reaches the immediate vicinity of the nest. It may be described as a rapid 'ti-ti- ti-ti-titititi'. Melcher (1952) recalled that when he was taking egg measurements the male perched on a nearby cherry tree and uttered this call continuously, while the female crept about in the bushes silent and almost unnoticed. U. A. Corti (quoted by Melcher) found that the churring call was not uttered in the immediate vicinity of the nest, rather that the bird moved to a distance of about 60 metres before calling, while Melcher himself found 20 metres to be the limit. The bird is, however, not always vocal: Rauhe (1956), after a fruitless half-hour search of habitat in Lower Saxony, suddenly heard the alarm churr only when a Fox Vulpes vulpes appeared. There is also a hard 'tcheck', similar to that of other Sylvia warblers. The song is a rather typical Sylvia warbling, perhaps most similar to that of the Garden Warbler and also somewhat like an improved version of the Red-backed Shrike's song (Melcher 1952). It has a rich tone, comparable to that of the Blackcap S, atricapilla (Fry 1970), with rapid short phrases reminiscent of the scratchy phrases of the Whitethroat, and not infrequently the alarm churr is incor porated into the whole. Melcher found these single phrases often varied and recorded occasional mimicry, fragments of the song of the Tree Pipit Anthus trivialis being emitted, as well as single calls 'dliii, dliii' with a timbre recalling notes in the song of the Nightingale Luscinia megarhynchos. Although the full song is at times uttered from deep cover, more generally a song-post overlooking the territory is chosen. This may be an exposed perch or the top of a well-foliaged taller tree or bush. From such song-posts the song-flight is conducted. This takes the form of an irregular fluttering flight, twelve metres or so above the ground, which may terminate at the starting point or elsewhere in the territory. Though infrequent, it is rather characteristic and may properly be considered a field mark. At the beginning of the breeding season song is most regular in the early morning and late evening. It generally ceases by mid- or late July. Birds arrive on their breeding grounds in late April and early May, Barred Warbler studies in slightly later in the eastern parts of the range, though arrivals are said to commence in the Moscow area from 18th April (Dementiev and Gladkov 1968). Nest-building takes place between mid-May and early June, the site chosen being normally very well concealed low down in a bush, but sometimes up to 2.5 metres above the ground (Dementiev and Gladkov). Of 20 nests examined by Gotzman (1965) in Poland, 15 were in twigs intertwined with tall sheltering grasses. Ten of these nest sites he studied in greater detail and obtained the following averages: total height of the bush in which the nest was placed, 97 cm (50-200); height of the nest above the ground, 44 cm (20-100); thickness of the branches on which the nest was placed, 13 mm (6-22); length of branches, 41 cm (15-9°)- Both sexes are said to build the nest (Witherby et al. 1938), though the male's share may be limited and the nest lined by the female alone (Melcher). It is a typical Sylvia nest, resembling a large Whitethroat's. An untidy structure, it is made of grass stalks and dried plant stems. On the outside the material is put together loosely and projects in all directions (see plates 14-15). The construction becomes tidier towards the inner cup, which is smooth and even and lined with very fine stalks and hair. The nest studied by Melcher had a cup measuring 8 cm in diameter and 4.2 cm in depth, and a total depth of 7.5 cm.

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