344 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1925 



bird is explained by its environment. It ploughs into the ground 

 after the manner of the ground chough, hammering the surface with 

 its powerful bill and securing its food by boring into the soil. And 

 since the soil is often frozen and difficult to penetrate, this species 

 of the plateau must have a sharper bill than the closely allied species 

 of the plains. 



That remarkable bird, the ibis bill, provides an excellent example 

 of how the bill of a bird is adapted to its method of securing food. 

 It is a high-altitude wader with a long hard and slender bill curved 

 something like that of a curlew. This bird is met with in the moun- 

 tain torrents that pour from Tibet into the Himalayan range. It 

 specially likes those places where the stream is broad and meanders 

 through a bed of stones. There it runs about upon the layer of 

 boulders, sometimes wading into the torrent up to its breast, thrust- 

 ing its long bill under the stones in the hope of finding insects be- 

 neath. Sometimes it curves its bill around the front of the stone, 

 sometimes inserts it from one side. The bill is an excellent instru- 

 ment for this purpose. Were it straight, it would not suit the round- 

 ness of the i)ebbles. The curve is a necessary feature of the 

 implement, and is excellently adapted to the habits of the bird, for 

 it is curved in such a way that it fits neatly around the boulders 

 when the bird is probing for food. 



The peculiar environment of the Tibetan plateau has caused some 

 of the high-altitude birds to change their customary habits, of life. 

 Some kinds, owing to the absence of trees, have become almost 

 exclusively village birds. Thus the tree sparrow is to be found near 

 every habitation. The accentors, which usually haunt bushes, in 

 Tibet live amongst houses and in streets ; also the rose finches, which 

 naturally like jungle, are frequently seen on the village walls. The 

 magpies are like house croAvs in the way they keep to the villages, 

 and, like choughs, they frequent precipitous cliffs. Many of the 

 wildest birds have lost their sense of fear. The rudd}' sheldrake 

 and the bar-headed goose, which in India are amongst the most 

 timid of birds, in Tibet swim about the ponds near the villages as 

 fearlessly as in a city park. The hill pigeons fed as boldly at 

 our Everest base camp as if they were the tame birds in a London 

 street. We observe the same tameness in the case of some of the 

 mammals. Wild sheep, for example, are naturally very timid, yet 

 at the base camp they came within 20 yards of our tents, and they 

 are said to visit the caves in the mountains, where they take food 

 from the hermits' hands. Thus we see how pliable is animal instinct. 

 This usual tameness must be due to the absence of persecution, and 

 shows that the sense of fear is not altogether innate, but is developed 

 as a result of persecution by man. , 



