298 BEITISH BIRDS. 



country and Central Abyssinia C. aquatorialis occurs^ which is somewhat 

 intermediate between it and the Common Swift. In its dimensions it is 

 exactly intermediate between these two species, and has the dark belly of 

 the latter^ but the less forked tail o£ the former. 



The Alpine or White-bellied Swift very closely resembles the Common 

 Swift in its habits. It is, however, much more of a rock bird, and is 

 rarely seen except amongst mountains. It delights to frequent the bare 

 heights, the stupendous passes and ravines, the perpendicular cliffs and 

 rocks, where, secure from all enemies, it can rear its young in peace. It 

 is generally a gregarious bird, and is usually met with in large or small 

 flocks. Like its congener it is a somewhat4ate summer visitor to Europe, 

 seldom arriving in Spain and Asia Minor before the last half of March, 

 and in Switzerland not before May, generally leaving again in August. 

 In Palestine Canon Tristram says that it arrives much earlier than the 

 Common Swift. The first time he noticed them was on the 13th of 

 February, when at Jerusalem he saw large flocks, apparently on migration, 

 flying north at a great height and with amazing rapidity. It is pro- 

 bably a partial resident in the valley of the Jordan, which may be regarded 

 as an outlying island or a peninsula of the Ethiopian Region which 

 stretches northwards far into the Palaearctic Region. The zoological 

 regions are bounded longitudinally by seas which are geographical boun- 

 daries, but their extent to the north or south is simply a question of 

 climate. The valley of the Jordan enjoys a tropical climate because it lies 

 below the level of the sea, and it consequently belongs to the Ethiopian 

 Region. 



As might naturally be expected from a bird which, small as it is, 

 measures nearly two feet in expanse of wing, the Alpine Swift is capable 

 of very rapid and powerful flight. It sometimes flies near the groiind, 

 especially in the morning and evening and in rainy weather, but at other 

 times it searches for its insect food in the highest air, occasionally going 

 beyond the range of human vision. 



The Alpine Swift is rarely seen on the ground and scarcely attempts 

 to walk, its long wings and short legs causing its mode of progression 

 to be little better than shuffling or creeping ; but if alarmed it has not 

 the slightest difficulty in instantly taking wing. The structure of its 

 feet makes it difficult for it to perch on a branch or horizontal surface 

 but against the perpendicular face of a cliff or tower it clings with the 

 greatest ease. The hole in which the nest is built serves as a roosting- 

 place for both birds, and, after the young are hatched, for the whole family. 



Like its British ally it is an early riser, and is often seen abroad before 

 dawn. It dashes in reckless haste along the face of the rocks, or darts 

 down like a feathered meteor to the plains ; then ascends far up into the 

 sky, wheeling in large circles, gliding smoothly along, turning suddenly 



