Page:EB1911 - Volume 22.djvu/988

  The salinity of the waters is relatively great, the highest recorded being 42.7 per mille (Gulf of Suez), and the lowest 36.2

(Perim harbour). The distribution is, speaking generally, the opposite to that of temperature; salinity increases from the surface downwards, and from the south northwards, and it is greater towards the western than the eastern side. This statement holds good for the Gulf of Suez, in which the water is much salter than in the open sea; but in the Gulf of Akaba the distribution is exceedingly uniform, nowhere differing much from an average of 40.6 per mille.

The movements of the waters are of great irregularity and complexity, rendering navigation difficult and dangerous. Two

features stand out with special distinctness: the exchange of water between the Red Sea and the Indian Ocean and the tidal streams of the Gulf of Suez. From the observations of salinity it is inferred that a surface current flows inwards to the Red Sea in the eastern channel of the Strait of Bab el-Mandeb, while a current of very salt water flows outward to the Indian Ocean, through the western channel, at a depth of 50 to 100 fathoms from the surface. In the Gulfs of Suez and Akaba, almost the only part of the Red Sea in which tidal phenomena are well developed, a sharply defined tidal circulation is found. Elsewhere the surface movements at least are controlled by the prevailing winds, which give rise in places to complex “transverse” currents, and near the coast are modified by the channels enclosed by the coral reefs. During the prevalence of the north and north-west winds the surface level of the northern part of the Red Sea is depressed by as much as 2 ft. The great evaporation going on from the surface probably causes a slow vertical circulation in the depth, the salter colder waters sinking, and ultimately escaping to the Indian Ocean. Extensive collections of the deposits forming the bed were made by the expeditions of the Austrian ship “Pola” (1896 and 1898). These were analysed by Dr K. Natterer, whose conclusions, however, have been disputed by a number of other investigators. The zoological collections of the “Pola” expeditions show that certain well-defined districts are extremely rich in plankton, while others are correspondingly poor; and it appears that the latter occur in districts surrounded by currents of relatively low temperature, while the richer parts are where the movements of water are blocked by irregularities in the coast-line.

.—A. Issel, Morfologia e genesi del Mar Rosso. ''Saggio di Paleogeografia, Congresso Geogr. Ital''. (Florence, 1899); “Die Korallenriffe der Sinai-Halbinsel,” ''Abhandl. Math.-phys.'' ''Gesell. Wiss.'', vol. xiv. (Leipzig, 1888); Meteorological Charts of the Red Sea (Meteorological Office, 1895); Report of the Voyage of the Russian Corvette “Vitiaz” (1889); “Berichte der Commission für oceanographische Forschungen,” 6th series, 1898 in vol. LXV. of the Denkschriften der K.K. Akademie der Wissenschaften (Vienna); also various notes and preliminary reports in the Sitzungsberichte of the Vienna Academy of Sciences; Report of the Voyage of H.M.S. “Challenger” “Oceanic Circulation,” p. 30; J. Hann, Klimatologie (1897), vol. iii. p. 76. (H. N. D.)

 REDSHANK, the usual name of a bird—the Scolopax calidris of Linnaeus and Totanus calidris of modern authors—so called in English from the colour of the bare part of its legs, which, being also long, are conspicuous as it flies or runs. In suitable localities it is abundant throughout the greater part of Europe and Asia, from Iceland to China, mostly retiring to the southward for the winter, though a considerable number remain during that season along the coasts and estuaries of some of the more northern countries. Before the great changes effected by drainage in England it was a common species in many districts, but at the present day there are very few to which it can resort for the purpose of reproduction. The body of the redshank is as big as a snipe's, but its longer neck, wings and legs make it appear a much larger bird. Above, the general colour is greyish-drab, freckled with black, except the lower part of the back and a conspicuous band on each wing, which are white, while the flight-quills are black, thus producing a very harmonious effect. In the breeding season the back and breast are mottled with dark brown, but in winter the latter is white. The nest is generally concealed in a tuft of rushes or grass, a little removed from the wettest parts of the swamp whence the bird gets its sustenance, and contains four eggs, usually of a rather warmly tinted brown with blackish spots or blotches; but no brief description can be given that would point out their differences from the eggs of other birds, more or less akin, among which, those of the (q.v.) especially, they are taken and find a ready sale.

The name Redshank, prefixed by some epithet as Black, Dusky or Spotted, has also been applied to a larger but allied species—the Totanus fuscus of ornithologists. This is a much less common bird, and in Great Britain as well in the greater part of Europe it only occurs on its passage to or from its breeding-grounds, which are usually found south of the Arctic Circle, and differ much from those of its congeners—the spot chosen for the nest being nearly always in the midst of forests and, though not in the thickest part of them, often with trees on all sides, generally where a fire has cleard the undergrowth, and mostly at some distance from water. This peculiar habit was first ascertained by Wolley in Lapland in 1853 and the following year. The breeding-dress this bird assumes is also very remarkable, and seems (as is suggested) to have some correlation with the burnt and blackened surface interspersed with white stones or tufts of lichen on which its nest is made—for the head, neck, shoulders and lower parts are of a deep black, contrasting vividly with the pure white of the back and rump, while the legs become of an intense crimson. At other times of the year the plumage is very similar to that of the common redshank, and the legs are of the same bright-orange. (A. N.)

 REDSTART, a bird well known in Great Britain, in many parts of which it is called firetail—a name of almost the same meaning, since “start” is from the Anglo-Saxon steort, a tail. This beautiful bird, Ruticilla phoenicurus, returns to England about the middle or towards the end of April, and at once takes up its abode in gardens, orchards and about old buildings, when its curious habit of flirting at nearly every change of position its brightly-coloured tail, together with the pure white forehead, the black throat, and the bright bay breast of the cock, renders him conspicuous, even if attention be not drawn by his lively though intermittent song. The hen is much more plainly attired; but the characteristic colouring and action of the tail pertain to her equally as to her mate. The nest is almost always placed in a hole of a tree or building, and contains from five to seven eggs of a delicate greenish blue, occasionally sprinkled with faint red spots. The young on assuming their feathers present a great resemblance to those of the (q.v.) at the same age; but the red tail, though of duller hue than in the adult, forms even at this early age an easy means of distinguishing them. The redstart breeds regularly in all the counties of England and Wales. It also reaches the extreme north of Scotland; but in Ireland it is very rare. It appears throughout the whole of Europe in summer, and is known to winter in the interior of Africa. Several very nearly allied forms occur in Asia; and one, R. aurorea in Japan.

A congeneric species which has received the name of black redstart, Ruticilla titys, is very common throughout the greater part of the continent of Europe, where, from its partiality for gardens in towns and villages, it is often better known than the preceding species. It yearly occurs in certain parts of England, chiefly along or near the south coast, and curiously enough during the autumn and winter, since it is in central Europe only a summer visitor, and it has by no means the high northern range of R. phoenicurus. The males of the black redstart seem to be more than one year in acquiring their full plumage (a rare thing in Passerine birds), and since they have been known to breed in the intermediate stage this fact has led to such birds being accounted a distinct species under the name of R. cairii, thereby perplexing ornithologists for a long while, though now almost all authorities agree that these birds are, in some sense, immature.

More than a dozen species of the genus Ruticilla have been described, and the greater number of them seem to belong to the Himalayan sub-region or its confines. One very pretty and interesting form is the R. moussieri of Barbary, which allies the redstart to the stone-chats (see ), and of late some authors have included it in that genus. In an opposite direction the bluethroats, apparently nearer to the redstarts than to any other type, are placed in the genus Cyanecula, containing two or three distinguishable forms: (1) C. suecica, with a bright bay spot in the middle of its clear blue throat, breeding in Scandinavia, northern Russia and Siberia, and wintering in Abyssinia and India, though rarely appearing in the intermediate countries, to the wonder of all who have studied the migration