268 A NATURALIST IN HIMALAYA 



boughs or climb about the trunks of the trees ; there 

 are some which make sallies into the air, others which 

 busy themselves in the undergrowth, others which 

 cling to the cliffs or hunt about the leaf-strewn ground. 

 Every nook is thoroughly explored ; the troop then 

 passes on and the woods are again deserted of life. 



These troops are to be seen at all altitudes up to 

 10,000 or 11,000 feet near the furthest limits of the 

 trees. In the summer season they are thin and im- 

 poverished since many of the birds separate to fulfil 

 the duties of the nest. Some of the more familiar 

 species then absent themselves from the troop. In 

 early spring they are strengthened by many visitors 

 from the Peninsula. Drongos, magpie robins, differ- 

 ent species of flycatchers then arrive to join in the 

 common throng. The birds utter a continual twitter 

 which serves to keep the troop intact ; often the notes 

 are very faint, perhaps beyond the range of the human 

 ear to detect. When alarmed, as when a gun is fired, 

 they often have the habit of sitting motionless in the 

 trees. It seems for the moment that they have gone ; 

 but soon they reappear and the woods again teem 

 with life. 



This habit of different species collecting into 

 gregarious flocks makes for the benefit of all. The 

 insects driven by the tits from the branches are 

 captured by the warblers, chats or flycatchers in the 

 air, or, alighting on the trunks, fall a prey to the 

 creepers ; others disturbed by the creepers escape to 

 meet a host of enemies. It is on a small scale the 

 same advantage that Bates and Belt describe in the 

 great flocks of hunting birds that traverse the forests 

 of Nicaragua and Brazil. Here bird associates with 



