Studies of Less Familiar Birds 148. Blue Rock Thrush by Geoffrey Beven Photographs by M
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Studies of less familiar birds 148. Blue Rock Thrush By Geoffrey Beven Photographs by M. D England and A. N. H. Peach (Plates 39-42) Watching from a crag over the stony slopes of southern Europe, the lone figure of the male Blue Rock Thrush Montkok solitarius (plates 39-40) is a handsome sight with blue-grey body and slaty-black wings and tail. In winter many feathers hare brownish fringes which wear off by spring, except in some first-year males, to expose a brighter and more uniform blue. The female (plates 41-42a) is bluish-brown above with faint cross-bars of grey-brown and paler below with rather broader bars, the throat being lighter and giving the appearance of dark markings on a light ground. This plumage is that of the typical subspecies, but there are others which differ in size, in the brightness of the blue in the male, and in the presence and extent of chestnut on the lower parts. The young have little blue, though some dark slate colour, and are mainly brown above and dark buff beneath with dark subterminal bars. The adult is about eight inches long; the bill, which aooears rather long and slender, and the legs and feet are black. RANGE AND HABITAT The breeding distribution of the European race, nominate solitarius, is southern Palearctic and includes Morocco, Algeria, Tunisia, Libya and perhaps the central Sahara, as well as the Iberian peninsula, south France, south Switzerland, Italy, the Balkans, the Mediterranean islands, Asia Minor, the Caucasus and Iran. Other races breed through the central Asian mountains to China, Korea and Japan, spreading into the Oriental region in Formosa and Malaya. Although the European race is mainly resident, some individuals winter in north and west Africa, chiefly the Sahara. The Asiatic races, however, are mainly migratory, wintering in rocky shrub steppes and dry savannah in north Africa and southern and south-eastern Asia south to Ceylon, Borneo and the Celebes (Etchecopar and Hue 1967, Henry 1955, Ramsay 1923, Voous i960). The species has not so far been acceptably recorded wild in Britain: one seen on North Ronaldsay, Orkney, from 29th August to 6th September 1966 was considered suspect because numbers are now imported as cage-birds (Brit. Birds, 60: 324). 303 BRITISH BIRDS The Blue Rock Thrush is very much a bird of the rocks, frequenting warm and barren boulder-clad hillsides, open rocky ground and gorges or cliffs between forests. In the Swiss Alps it is found only in warm stone quarries in Tessin. Breeding occurs at 9,600 feet in the High Atlas and Iran, up to 12,500 feet in the Himalayas and also down to sea level in some areas: in Japan the species is seen only along the rocky sea coasts. In remote areas it is very shy, but in towns in southern Europe where the Blackbird Turdus merula is absent it frequents the roofs of houses, churches and castles, even perching on stone monu ments in busy squares; in Japan it is numerous in coastal fishing villages. It has been suggested that this was the 'sparrow alone upon the house-top' in the Holy Land (Psalm 102, 7). Thus it is far less restricted than most species in its altitudinal range, but generally favours warmer, more barren and lower habitats than the Rock Thrush M. saxatilis (Vaurie 1959, Voous i960). In winter it still frequents rocks on hills or the sea shore, but will make do with quarries, ruined forts, unoccupied buildings, brick kilns and piles of stones, often roosting in caves or under the roofs of houses. HABITS AND FEEDING Usually solitary, the Blue Rock Thrush sits erect on a rock or other point of vantage. The wings are drooped and flaunted and the head raised. When approached, it dives away out of sight with darting flight. It watches for prey from its rock perch and flies down to pick it off the ground or makes sorties after flying insects, sometimes merely jumping up to catch them. Occasionally, it runs along a stone wall at speed, perchine for a moment on each parapet. The Indian race. M. s. pandoo, has a curious habit of frequently dipping forward, as if in a courtly bow (Henry 1955). In contrast to the Rock Thrush, this species is said to perch less frequendy in trees or shrubs in Europe than in Asia (Voous i960), but we certainly recorded it singing from trees and posts in Portugal. In habits and voice it seems to occupy an intermediate position between the typical thrushes Turdus and the chats Oenanthe and Saxkola (Etchecopar and Hue 1967, Harrison 1954). Lack (1954) suggested that, as the tail is neither red nor strongly vibrated, this species is more closely related to Turdus than the Rock Thrush which seems more like a large redstart "Phoenicurus sp. The food is mainly insects which live on the ground and among the rocks, but spiders, earthworms, snails and occasionally even small snakes and mice are taken; also many berries are picked from low bushes. We observed caterpillars, large grasshoppers and lizards being brought to the young in the nest in Portugal, the adult some times foraging two or three hundred yards away. Some of the lizards (plates 393-40) were so large that it was difficult to believe they could i"4 BLUE ROCK THRUSH STUDIES be swallowed. On the sea shore Blue Rock Thrushes feed like waders among the rocks, pebbles and seaweed and around tidal pools, taking sea snails, small crustaceans and marine worms (Voous i960). VOICE AND DISPLAY Several call notes are uttered in circumstances of stress and alarm: these include a deep chat-like tac-tac or tchuck, a plaintive and sibilant tseee, and a uit-uit somewhat similar to notes uttered by the Nuthatch Sitta europaea. In north Italy a female was heard frequently giving a call identical to the rattling alarm notes of a Blackbird over a period of 20 minutes (Harrison 1954). We noticed adults making a musical chuc kle just before arriving at a nest containing young. The song is deliberate, loud and melodious, recalling that of a Blackbird or Mistle Thrush T. viscivorus, but the phrases are simple, short and repetitive. Although the bird normally utters it from exposed rocks, it may also do so from the tops of electric pylons and the branches of trees. Often one will sing during a vertical display flight or while flying across a valley; the song carries far across the gorges. When courting, the male indulges in slow volplaning flights which show off his blue plumage to advantage in the sunlight (Whistler 1941) or he may sail on open wings like a Bee-eater Merops apiaster. BREEDING Nests are usually built in crevices in rocks, cliffs and buildings, under stones or up to at least ten yards inside caves. The site is often on steep, precipitous ground and frequently inaccessible. The well-hidden structure is a shallow cup of roots and dry grasses lined with finer roots. There are three to six eggs, usually five, very smooth in texture with a fine gloss. The ground colour is very pale blue, sometimes unmarked, but often speckled, mostly at the broad end, with minute brownish red spots. Average measurements are 27.5 x 20.5 mm. (Etchecopar and Hue 1967). We found three nests in central Portugal. In May 1964 there was a remarkably high concentration of Blue Rock Thrushes in a rocky valley below a dam known as Barragem de Castelo do Bode, on the Rio Zezere near Constancia, where conditions for watching were particularly good and where the dam had probably increased the amount of suitable habitat. Here I. J. Ferguson-Lees, after several hours' watching, concluded that there were probably nine pairs visible from the dam; two pairs had fully fledged young. A nest found on 1st June was in a high stone wall by a road below the dam. It was built in a hole draining the road above and was about 15 feet from the ground. Both adults were bringing food, including caterpillars; the male left soon after feeding, but the female often remained, presumably to 5°5 BRITISH BIRDS brood the young. The photographs on plates 39~42a were taken during May 1965 at a second site, the nest being nine feet up in a hole between the stones of a wall which was part of a road bridge near Castelo de Vide; the triangular hole was about four inches across. The male, from his plumage probably a first-year bird, often sang from the top of a pole on approaching the nest. Eventually the four young were enticed from the nest by his repeatedly coming without any food. On nth May he led them upwards to the top of the wall; their ability to climb the sheer rock was amazing. In 1965 several pairs were nesting in the Castelo de Vide and in a barren area near the town. The third nest (plate 42b) was found on 17th May on a sloping ledge three feet up between two rocks with an overhanging rock slab at the back of a cave. This structure was an untidy cup shape with long grass stems sticking out from the base, made largely of coarse grasses, but lined with finer ones. It contained three pale blue eggs, two with small brownish spots and the third quite unmarked. While we examined the nest, the female remained near-by, calling in alarm; on the other hand, Leveque (1956) found that the parents kept silent when he disturbed them from a nest with newly hatched young in France.